Building an AR: Priorities in Accuracy?

[JeepHammer]

I have built and shot the AR platform since the very early '70s.
I have figured a few things out in that time...
I built small arms for the Marines for nearly 16 years.

With respect to others, I know I'm going to write some things that some will disagree with...
Please don't think I'm attacking anyone in particular or directly, I am not.
Please don't attack me.

1. Shooter,
Depends if you are bench shooting, Rested, Freehand.
Bench rifles can be hyper accurate, it takes time and experience to build one that is hyper accurate.

Field & General rifles are much easier to build.

2. Ammo,
The 'Best' ammo will be like any other rifle,
Once it's built, you tray a few brands,
Run different weights and velocities through a cronograph,
See how they print down range.

3. optic/sights,
This is a sticking point for most people.
In Europe, they have a $1,000 optic on a $200 rifle and shoot well.
In America, we buy $1,000 rifles and glue on a $100 optic HOPING that optic imparts some magical accuracy on the rifle itself, or the shooters abilities...

4. trigger,
I shot competition for several years with a 'Worked' stock trigger, and about all my field/rested rifles have stock triggers now (that have been worked).

I've spent up to $400 for 'Match' triggers that did absolutely NOTING a 'Worked' factory trigger wouldn't do for $2 in dremel tool bits and some time.

5. Barrel,
You will loose about 300 to 350 FPS speed between a 16" & 20" barrel.
If you use a post front sight, you lose 4" of sight radius, making the rifle inherently less accurate.

The barrel is the single most important thing you can spend money.
If you don't have an accurate, rigid barrel with good rifling and no restriction points in the bore,
Then you simply aren't going to build an accurate rifle no matter what you pay for all the other parts.

The 'Easy' way to sub MOA rifles is to start with a full diameter National Match barrel,
But keep the rifling twist rate REASONABLE.
Some idiots are making up to 99 grain bullets for AR-15,
And the most usable will be between 50 and 60 grain at the ranges (and beyond) you are talking about.

6. Freefloat,
This can be a BIG DEAL *IF* you have a 'Skinny' barrel.
If the barrel you want to use is undercut, the pressure of the handguard springs will effect (bend) the barrel.

If you use a full diameter barrel from chamber to gas port,
Then taper down a little for the gas port,
Stay full size to the muzzle cut,
Then the hand guard springs, or having the hand guards sitting on something usually won't affect your point of impact.

If you have one of those undercut barrels (many early military, civilian and guys that had a weight restriction in competition) will have SEVERELY undercut barrels to save weight.
These barrels will move around under the tension of the handguard springs, sitting on bags or rests, ect.
It's a REAL good idea to free float a 'Skinny' or undercut barrel.

7. chamber,
This usually isn't an issue.
If you have the ability to use a chamber reamer,
Then you have the ability to pull the chamber nut off the barrel and cut a couple more threads,
That moves the barrel back in the chamber nut,
And it moves the chamber backwards.
Cut a couple threads off the back of the barrel and put the chamber nut back on.

You simply use a chamber reamer to cut the chamber for headspace and you are done,
Unless you want to mess with free bore.

Everyone has at least three opinions about freebore and the .223 Rem./5.56x45mm round, so I'm not even going to get into that fight...

8. 16 vs 18 vs 20 inch barrel,
20" barrel will give you a MINIMUM of 300 FPS with about any load, and having that extra velocity at the muzzle is always a good idea.

There isn't much to be gained with a 24" barrel,
Although you will gain a little between 20" and 22".

It will also be MUCH easier to find a 20" H-Bar (heavy barrel, No undercut) than it will be to find a 16".
Most guys with 16" H-Bar start with a 20" and cut it down themselves.

I would never recommend cutting the barrel lenght under 20" unless there was some competition class rules about 'Carbines', and I would have as much barrel as the rules allowed for...
Barrel is accuracy.

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In SPECIFIC,
NO UNDER CUT BARRELS.
If the barrel isn't full diameter between chamber and gas block,
Then full size between gas block and muzzle, I don't consider it for an 'Accuracy' Rifle.

TRUE THE UPPER RECEIVER!
True it for bore, And for front face where the barrel shoulders in the front threads.

EVERY single upper I've seen in several years DOES NOT have the front of the receiver trued after the coating process.
This makes the barrel 'Cocked' at an angle in the upper,
And you will NEVER get the optics aligned with the barrel.
Change range, change point of impact, it's probably a thicker coating on one side of the receiver mouth than the other...

USE A SOLID OPTICS MOUNT!
There is NOTHING worse than a cheap optics mount for accuracy.
Long, thin stems raising the optics center line up are unstable, just a fact of life.

Figure out how much rise you need once you have a cheek weld,
Then buy a good, solid optics mount that keeps the tube at that eye level.

Proper cheek weld SHOULD align your optics each and every time with your eye.
If you have to move your head up and down to find center of the optics,
Then you are never going to do well...

HONE ALIGN THE RINGS!
Most times, the RINGS don't line up with each other.

This puts a curve, bow, 'S' twist in the tube when you tighten down the clamps.
With all this idiotic 'Tactical Black' finish now days, the tube heats up, the bow, twist, curve gets WORSE as the tube expands with heat.

A lapping bar in 1" or 30mm and some fine grit & grease will hone the rings STRAIGHT with each other.

If you trued the upper receiver barrel mating surfaces,
The barrel is now straight with the upper receiver,

Get a HEAVY mount for the optics,
Lap hone the rings STRAIGHT with each other and the upper,

The upper *Should* shoot in a straight line no matter what the range...
Barrel, Upper Receiver, Optics have to be aligned with each other, or you will NEVER shoot in a straight line at different ranges.

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A Word About 'Sights'...

If you are using apature sights, then move the front sight to the END of the barrel.
This increases your sight radius, and makes the rifle inherently more accurate.

If you are using 'Magnified Optics' ('Scope'),
Then consider your usage, there are three rules to a 'Good Scope'
1. Application.
2. Application.
3. APPLICATION!

If you are TARGET SHOOTING, and nothing else,
Then those large, sticking out in the way target knobs with 1/8" or 1/4" 'Clicks' are OK.

If you are STATIONARY hunting, where you have time to make adjustments BEFORE you take the shot,
Then get turrets with CAPS, NOT EXPOSED KNOBS.

If you are 'Walking Hunting' or Mountain hunting,
Then consider FRICTION knobs, not 'Clicks',
LOW TURRETS that don't snag on brush, get banged around, ect.

Friction knobs allow you PRECISE adjustments, where 'Clicks' can be a little one way or the other...
I've found that my 'Mountain/Walking' rifles with a range finding reticle, like to be zeroed at about 200 yards,
Using the hold over in the reticle for those shots where you don't have time to mess with 'Knobs' works pretty well.

Again, solid mounts/rings, trued with the receiver,
And true the receiver so the barrel goes on straight and you will be pretty well ready to find a load that works for you.

[DarthNul]

Interesting post and lots of good advice here.

I'm not sure if it matters but if you really plan to run nothing but white box Winchester ammo through the gun, how would you ever know if it's actually accurate or not? I've got nothing against WWB. Pretty much everybody shoots it sometimes. It may be accurate "enough" some/most of the time, but it's not likely to be anybody's first choice for accuracy.

Now for my $0.02: If your versatility plans includedoing any sort of rapid fire shooting, get a heavy profile barrel. A heavy barrel will keep your groups tighter longer than a standard profile or pencil barrel. I don't care how accurate a skinny barrel is cold-bore, once you get three or more shots downrange quickly they'll start to wander if you don't pace yourself or stop and let it cool down.

[JeepHammer]

Yup, A good barrel is a thing of beauty and a joy for the next 15,000 rounds or more...

Since every firearm is about ACCURACY,
Then spend your money on an ACCURATE BARREL.

Then get that barrel in the upper receiver SQUARELY.
The same 'Bolt Rifle' basics apply to the AR upper,
Square bolt bore with the front face,
So the barrel is square with the upper receiver,

And pay attention to the locking lugs on the bolt.
When the bolt hits 'Battery', it needs to be square with the barrel bore.
I see TONS of guys that won't square the upper reciever,
Then complain the rifle shifts 'Zero' when they change distance/range.

This is simply a front receiver that isn't square/true with the barrel.
The optics/sights are on a different base line (line of sight),
With the barrel bore.

Virtually All AR upper receivers have the finish MIS-Aligning the barrel with the upper receiver,
So that finish has to be lapped or lathe turned off to true/square the front of the upper receiver,
Then the barrel can mate SQUARELY with the upper and you are off to the races!

Once upper and barrel are square/true,
Then 90% of the work is done.

Again, lapping the bolt lugs and the chamber nut lugs to fit together make a big difference,
And this is pretty easy also.
I use an old bolt carrier modifed to turn a bolt aligned with the upper/bore and lap in the bolt to fit the chamber nut with a hand drill.
Takes about two minutes...

When the bolt locks up in the SAME PLACE, EVERY TIME,
Consistency shoots WAY UP, and accuracy will do the same.

Once the upper, barrel and bolt all lock up in a straight, true, square line, you have the tiger by the tail!

The barrel nut, the hand guard side nut, I also lap.
My lapping bar allows me to lap the inside barrel nut surface so the barrel nut sits SQUARELY on the chamber nut holding the barrel in the upper.

Again, this is about a 2 minute process with the correct lapping tool and a hand drill...

This means the barrel nut fits SQUARELY against the chamber nut holding the barrel into the upper receiver.
Again, this is a consistency thing,
When the barrel/barrel nut/upper heat up, the barrel nut compression holing things together doesn't allow the barrel to cock sideways/diagonally/vertically in the upper receiver.
Point of impact doesn't shift as the unit heats up under use.

Accuracy is all about the bore,
And how the bolt locks up the chamber,
And what those components do when they heat/cool...

It's funny to me to see guys have zero shift 2" when the rifle lays in the sun...
Still swearing that because they paid a ton for it, it has to be the ammo or optics.

Cheap, light weight optics mounts, cheap optics tubes, will shift when they heat up,
but when they are using IRON sights and zero shifts,
You KNOW the barrel moved in the upper shifting the zero around,
And they just flat deny it can happen.

Growing 'Longer' as it heats up is one thing,
Shifting point of impact around is something else entirely...

[jrucker2]

Wow thanks! That is a lot of detailed info, it is very interesting. Some of it may be a little overkill for my purposes, but definitely get to know if I decide to build a hyper accurate bench rest rifle in the future. I guess my greatest take away from this thread is that I should focus my money on a barrel a quality optic and mount, Quality ammo and lots of range time. This is a great Takeaway so that I don't end up spending all of my rifle budget on $300 triggers, fancy buffer springs, exotic bolt coatings and thus having little left over for a barrel in optics.

Just an update on my Build: I picked up an Anderson lower and lower parts kit yesterday for 60 and $50 respectively. This morning I ordered a Anderson buffer tube kit on sale for 25, a magazine 15, a adjustable stock for 35, and a charging handle for $15. That being said, I'm coming in quite a bit lower on the budget Than I expected and hopefully will have more to put toward the barrel.

I'm planning on installing the barrel myself once I get to the portion of the build. That being said I'm not completely following you on lapping the upper to make sure that it fits square with the barrel. Do you know of any YouTube videos where they show this process?

Thanks again for the great information.

[4V50 Gary]

I was talking with another classmate this week about that AR that our classmate had that keyholed badly. He told me that the fellow was using steel case ammo. That ammo gouged the receiver (he didn't have a M-4 carbine type receiver). I'm now wondering if that bullet was undersized by a few thousandths or if it had a steel insert that was unbalanced or threw the projectile off.

[JeepHammer]

'Steel Case' gets used a lot...

Actual steel cartridge case, or steel jacket on the bullet (Brass Washed or copper plated to make it look like a copper jacket bullet)

Unless you are buying American made ammo, take a magnet with you...
Caliper to measure the bullet with wouldn't hurt either,
A lot of the 'China' and 'Russia' ammo is over/under size bullets.

Even with a actual copper jacket, a lot of the 'Russian' (eastern European) ammo has a large hollow in the nose of the bullet that keeps the rounds from stabilizing like a full length core would.
The nose flattens, angles sideways, the bullet tumbles.

High velocity, super fast twist rate barrels, and thin bullet jackets don't get along.
At 3,200 FPS, fired from a 1 in 7 twist barrel,
The round is spinning around 300,000 RPM.

Varmint shooters went through this with thin jacket bullets,
The rotational forces throw the jacket off the bullet, the bullet doesn't stabilize.

High velocity also strips a thin jacket off the core,
The jacket material simply can't withstand the forward movement velocity,
And the rifling becomes a 'Reamer', sheering the copper off the jacket, the bullet becomes unstable since it didn't hold the rifling.

If you find copper 'Shards' when you clean, no matter how small, you are probably 'Cutting' the jacket off the bullet
Between grooves/lands sheering the copper jacket (in 12 places on a 6 groove barrel),
Combined with THIN copper jackets, you can cut the copper jacket on the bullet into ribbons of copper that fly off the core when you fire.

This is PARTICULARLY difficult when you shoot thin jacket 'Varmint' bullets at super high velocity through a fast twist barrel.
The copper is sheered into strips that can no longer cling to the core, and you wind up with a 'Smooth Bore' bullet exiting the barrel, followed by copper strips.

The 'Trick' when you find 'Key Holes' is to figure out what is going on since there is more than one way to screw up the bullet...
The only way to be sure is use a backstop that catches the core, see if the jacket is still on the bullet IN ITS ENTIRETY,
Or of there are pieces of the jacket missing.

See if the rifling is true, or if it's 'Smeared', a sign the twist rate is too much for the velocity/pressure the bullet is being forced down the rifling,

See if the nose collapsed sideways, or if it stayed true and mushroomed evenly.

Spread a sheet or tarp out in front of the rifle muzzle,
See if you are getting copper shards, A sure sign the bullet jacket is being sheered off the bullet core.

Another thing you can do is take a CONCENTRIC bullet,
Bullet lined up DIRECTLY with the center line of the case,
And set LONG in the case, crimped into place...
(you will need a special tool for checking the bullet to make sure the 'Test' round is concentric, it uses a dial indicator to detect 'Wobble' as the round is rotated in the test jig.)

Put that concentric 'Test' cartridge in the chamber,
ROTATE it about 1/8 turn, back and forth a few times,
Pull the 'Test' cartridge and look for a 'Rub Mark' on the bullet.
This will tell you if the 'Throat' of the barrel is deformed.

If you get a nice ring around the bullet with 1/8 turns,
Then the throat is concentric, not eroded away or damaged on one side, slamming the bullet sideways, deforming it as it enters the rifling.

If you only get a 1/8 or 1/4 turn rub mark on the bullet,
Either the throat to the rifling is deformed,
Or the chamber isn't square (In Line) with the rifling/bore.

[JeepHammer]

Just a little bit of HISTORY...
So the reading challenged should skip this post, they will only be bored...

The ORIGINAL AR-15/M16 was built to handle a 5.56mm (.224) bullet that weighed 52 Grains.
Rifling was 1 turn in 14 inches. (1/14 twist)

1/12 (1 turn in 12 inches) was the 'Standard' varmint rifle twist rate, using 40 to 50 grain bullets on the Civilian Market,
Chambered as .223 Rem.

The Military version increased the chamber pressure by 10,000 pounds.
NATO/Military 5.56 is 10,000 pounds MORE pressure than 'Civilian' .223 Rem rounds,
Which is why you shouldn't shoot 'NATO' in a .223 Rem. chambered rifle... Nothing like over pressuring the barrel/receiver each and every time you fire a round.

It's the 'Catastrophic Failure' roulette when you shoot NATO 5.56 surplus through a .223 Rem rifle...

---

Now, the US military, and NATO, deciding to use a cannelure bullet at 3,100 to 3,300 FPS wasn't arbitrary...
The Geneva Convention (Hague Accords) prohibits anything 'Fragmenting', 'Hollow Points' or any other kind of bullet that causes undue damage/suffering.
(A 'Kinder, Gentler Bullet'. Schizophrenic thinking.)

By ramping up the 'FMJ' with a cannelure to 2,800 FPS,
The FMJ bullet TUMBLES in the body cavity, creating a catastrophic wound channel.

The heavier base causes the bullet to 'Yaw' (turn sideways) when the nose encounters the resistance of a target.

When the bullet exceeds 3,100 FPS,
The bullet breaks at the cannelure, creating TWO wound channels.
This sidesteps the 'FMJ/No Fragmentation' rules laid down.
It's considered an 'Unintentional Consequence'...

(I have no opinion here, just relaying facts.
If an enemy combatant dies or is incapacitated by a single round after putting on the uniform and declaring war on the US/NATO, then he gets what he gets...)

The Russian/USSR/Warsaw pact countries did something similar,
A hollow air space between bullet core and jacket,
The nose flattens out blade like, yawing the bullet to make sure it tumbles...

The AK47/SKS/AK74 is NEVER going to develop the muzzle velocity the AR15/M16 has, so this was there version of 'FMJ' to inflict maximum damage.

---

Back to internal ballistics of AR style rifles...

Therefore, while the civilian versions had a slightly tighter twist rate, it had MUCH LESS pressure pushing the bullet.

Result... Slower bullet, better chance for the bullet to grasp and follow the rifling,
Especially with thin jacket 'Varmint' bullets.

-----

Now, the military being schizophrenic,
Decided to use MUCH HEAVIER bullets, which took even higher chamber pressures to push at predetermined velocities...

The reason being, they didn't want to change ballistic tables/sights,
So they mandated higher chamber pressures to keep the HEAVIER bullet at the same velocities.

---Current NATO 5.56 rounds can exceed .223 Rem MAXIMUM pressures by 15,000 pounds!

(That GREATLY increases the chance of that 'Cheap' surplus NATO ammo blowing up your .223 Rem rifle---)

This didn't work, as usual for NATO/5.56 rounds...
The higher pressures/slow twist rate (1/14) didn't stabilize the longer, heavier bullets.

Their solution was a faster twist rate barrel to stabilize the longer, heavier bullet.

The thinking being, heaver bullet means longer bullet, more load bearing surface to contact the rifling,
So they could turn the bullet faster without stripping the jacket off... and the bullet stabilized...

The M16 rifle became accurate again.

This madness continued, up to 77 Grain bullets in 'Standard' issues, and continuing to increase twist rate...

Now we have 90+ grain bullets, and 1/7 twist rates,

--Trying to shoot the old standard,
a 55 grain, thin copper jacket bullet doesn't work since the jacket gets stripped off the core by the rifling...

-----

And, the military being schizophrenic, decided to hack off the barrel from 20" down to 16" then 14 inches!

A 'Carbine' was never intended to be an 'ACCURATE AT LONG RANGE' main battle rifle (or civilian rifle, for that matter),
Never was, never will be...

It's a common sense thing...

Trying to get 3,300 FPS out of a 14" or 16" barrel is just STUPID when you are using ammunition designed for 3,300 FPS out of a 20" barrel.

----

Now, some say you only loose 50 FPS per inch of barrel reduction...
That is patently FALSE.

A chronograph will QUICKLY tell you 20" to 16" barrel you will loose between 300 & 400 FPS with exactly the same ammo, in exactly the same twist rate barrel.

The rate of loss INCREASES as you cut down to 14" barrels,
But that point is moot since the common LEGAL barrel length is 16".
The pressure is HIGHER with the bullet at 14" instead of 20", So you are dumping HIGHER PRESSURES with shorter barrels.

----

The INVERSE is NOT the same either,
Moving from 20" barrel to 22" barrel, you will pick up about 75 FPS per inch,
But moving from 20" to 24" will net you about 50-55 FPS average increase in muzzle velocity.

Not saying that ACCURACY doesn't go up with a longer barrel,
But 'Ideal' barrel length is between 20" and 24", depending on what kind of shooting you will be doing.

With more than 24" (over a standard 20" barrel) will only increase velocity about 35 FPS per inch, and decrease with length,
Not worth getting a stupid long barrel custom made beyond 24" that costs a fortune.

Nothing like ordering an $800 barrel and having a net muzzle velocity increase of 35 FPS for the inches,
Saving $500 is more important at some point unless you are going for 'Extreme' velocity claims (Bragging Rights)...

Ever try and manage a 30" barrel?
Nothing like trying to swing that thing around and NOT crash it into something/someone...

With a 30" barrel, I had a net bullet velocity increase of 18 FPS an inch over a 20" barrel...
Not worth the extra $500 and a pain to manage,
but I did have muzzle velocity bragging rights right up to the time I cut $500 off the end of that barrel...

I guess I could have pumped up the round I was firing to pressure that barrel up,
Then worried about overpressure issues...
And see EXACTLY where the common bullets started to come apart,
Then switched to some exotic bullet that cost $2 or $3 a piece before they were loaded into a case...
And had increased rifling wear from harder bullets, ect.

There is cost/benefit analysis there somewhere...

----

So, the short of it is,
If you intend to shoot the REASONABLE WEIGHT BULLETS on the common market,

Then you don't need the 1/7 twist barrel.

Slower twist rates will stabilize a lighter weight bullet just fine,
Just like the first 1/14 and 1/12 rate barrels did, and still do.

You don't need idiot long barrels,
But then again, you CAN NOT expect the same muzzle velocity out of a 16" barrel you will get with a 20" barrel.

*IF* you are hunting hogs, or shooting long REASONABLE distance, (300 to 600 yards)
Choose a 1/9 or 1/10 barrel, 20" to 24" long,
These will be a good length, accuracy, velocity for bullets in the 55 to 65 grain range,
More than enough to put down a hog or deer,
And will stay accurate out to 600/800 yards, depending on the bullet you choose and it's ballistic coefficient.

VARMINT shooters usually stay under 600 yards,
They also use lighter bullets they can push faster with any given length of barrel.

Most guys (out side of chipmunk shooters) use bullets in the 45 to 55 grain range, and usually shoot 20" to 24" barrels in the 1/9 or 1/10 range for good accuracy.
Heavy enough bullets to carry well and retain energy at the target,
but light enough for good muzzle velocity WITHOUT hamming the guts out of the rifle.

Shooting a 30 or 35 grain bullet in an AR is just silly...
Nothing like hitting a blade of grass or weed stem and having the bullet explode or take off to parts unknown.

The same is true for bullets above 65 grains,
If you want to shoot 1,000 yards, start with a .30 cal instead of an AR-15.

Shooting a 75 or higher bullet out of a .223 bore is NOT what the rifle was designed for in the first place...

Shooting a 90+ grain bullet out of an AR is stupid beyond reason, since the rounds won't fit in the mag anymore,
And you turned your AR into a 'Load One, Shoot One, Repeat...' rifle, with no follow up shot for that second coyote or ground hog...

If I wanted a single shot, I WOULD NOT have started with a direct gas impingement, rotating bolt, hooded chamber semi-auto to start with...

This is not only a cost/benefit thing, it's a common sense thing...

[Clark]

A) I have 3 AR-15s with NATO chambers that cost a median of ~ $1,000.

B) I soldered a surplus thin little $40 22LR 16" twist barrel from Numrich onto a bored out barrel stub of a $50 1903 Turkish Mauser from BIG5, bent the bolt, drilled and tapped for scope. I used my .223 reamer custom from Manson with .250" neck and .05" shorter than SAAMI throat.
$90 invested.


A) The $1,000 AR15s have never shot below 1.05 moa in the last 20 years of trying.

B)The $90 short chambered Mauser will not only shoot sub moa, it averages sub moa.

[JeepHammer]

The old saying used to be,

"You pay a generous PREMIUM for a good barrel,
And the rifle maker/gunsmith throws in the rest of the rifle to sweeten the deal."

--------------

I just shot my 'Junk Parts' AR yesterday afternoon,

Discarded Military 5.56 barrel, 20" long.
The guy sold it to me as 'Salvage', all the small parts were still on it, gas block flash hider, chamber nut...
Paid $50 for it.

Chamber throat was 'Out Of Tolerance' (poor chambering or eroded), Rifling on the other hand was quite crisp.
1/7 twist, which is a little tighter than I like,
And it was an H-bar barrel with no undercut between chamber and gas block pad...

I took the chamber nut off the barrel, shaved about 0.030" off the barrel at the threads, adding threads,
Cut 0.030" off the chamber end of the barrel,
And rechambered the rifle using a QUALITY chamber reamer, closing up freebore a little in the process.

Screwed the chamber nut back on it, checked headspacing,
Checked to make sure the gas tube was going to seat in the bolt carrier without bottoming out,

Stuck it in a flat top upper that was laying around here, a take off from a customer that didn't take his parts with him,
And generally went rooting through the 'Spare Parts' boxes to find enough 'Widgets' to put the thing together.

It DOES have a full, free floating barrel sleeve attached to the barrel nut,
And I am bench shooting with bags.

A $100 Simmons optic on top, 6.5 magnification,

And commenced to run some of my new hand loads through it.
This is the third trip to the range for this rifle,
The first trip, 1.1 MOA in 10 each, 10 shot groups (100 Rounds,
(not counting occasional 'Fliers' where I loose concentration, have to fart, see a pretty birdie or something shiny, hear a motorcycle going down the county road behind me, ect. where it's OBVIOUSLY my fault and not the rifle),

The second trip, 7/8 MOA, 10 each 5 shot groups.

Yesterday, the average 10 shot group could be covered with a dime or a penny...

Shortened freebore, rounds loaded to SAAMI 2.260,
All brass fired at least twice before,
Most of it military surplus,
55 Grain Hornady V-Max, medium crimp and no cannelure,
Winchester Small Rifle Primers, some old, some new.

First set was 25.0 Benchmark,
The second was 26.0 Benchmark,
The third was 26.5 Benchmark.

Muzzle Velocities are averaging 3,036 FPS on the last 100 round set,
With a velocity spread average VERY acceptable, slowest to fastest was 136 FPS,
VERY CONSISTENT with the Benchmark and WSR primers, medium crimp.

I did swab the bore every 10 rounds or so...

This is NOT some high dollar 'Hanger Queen' that only gets out of the case for 'Competition',
This is a collection of mis-matched parts that have only been worked in enough to function together...
I don't have $300 in this particular rifle, it's mostly take off parts from other folks' rifles they left behind,
And a $120 stripped lower receiver from the local shop.

----------

I'm SO SICK of hearing about 'Tactical Black' rifles from everywhere, like 'Tactical Black' makes things more accurate or better to use somehow...

I think I'll paint this one bright blue...

I thought about 'Pink', but I live in Indiana, and they just passed a law making refusing goods/services perfectly legal to anyone that's not your 'Religion'...
Of course aimed a gays, but also being used for guys from different churches to crap on each other...

Bright blue or bright purple shouldn't get me cut off from the local convince store when I want coffee or smokes...

And it will be a poke in the eye for all those 'Tactical Black' guys that infest the ranges trying to figure out why their 'Tactical Black' rifles aren't hitting anything!

[cryogenic419]

Here are the factors I am aware of in order by my current understanding:

1. Shooter
2. Ammo
3. optic/sights
4. trigger
5. Barrel
6. Freefloat
7. chamber
8. 16 vs 18 vs 20 inch barrel

Obviously the shooter is the most important part of the equation. You can have the finest rifle in the world but if your skills are lacking, you will never fully realize the accuracy within that rifle. I don't think enough emphasis can be placed on ones ability. Most of the guns are more capable that people will ever realize. I always like to use guitar analogies. Take Slash, Carlos Santana, Eric Clapton...they all play pretty pricey guitars. Take away the fancy guitars and give them el cheapo beginner guitars. I betcha they still play as well on those guitars.

For the distance you mentioned I don't see barrel length making any real noticeable significant difference. If you are looking for accuracy, you are probably going to want to cross off anything chrome lined. Not saying they can't be as accurate, they just generally aren't as accurate as their non chrome lined counterparts. Freefloating a barrel tends to help with accuracy, but realize that just because it is free floated doesn't guarantee a sub par barrel will now become a tack driving force to be reckoned with. If you are striving for accuracy look into a Wylde chambered barrel. You can shoot .223 or 5.56 in these, and it seems to provide a bit more accuracy that your standard .223 or 5.56 chambers. That is not to say the other chambers aren't accurate or have the potential to be, they certainly do. Twist rate is always a fun debate. My experience is 1:8 will let you shoot a wide range of bullet weights. Probably the biggest factor in barrels is who made the thing and do they do quality work? Quality does not always mean super high priced.

Ammo. Find something that works well in your gun. For some it might be as simple as trying 1 brand of bullet, getting what they see as acceptable results and calling it a day. Others might spend months or years and hundreds if not thousands of dollars chasing accuracy.

A good trigger is worth its weight in gold. I suppose its possible you can be a hell of a marksman with a standard AR trigger. Rest assured none of the top shooters out there are doing what they do with a stock trigger and that insanely heavy pull weight. There are some pretty decent options out there, ranging from $50 to $300.

Optics/sights. Some folks buy more optic than is practical and spend way more than is necessary, I'm sure the industry appreciates this greatly. You can have the best and most highpowered optics in the world, doesn't mean you're going to be a more accurate shooter. If you know you're only going to be shooting 200 yards it wouldn't make sense to buy something geared for 1000+ yards in combat conditions. Find something more suited for the task and distance at hand. Fancy illuminated super duper tacti-cool mil dot front focal plane reticles have their place in the world I suppose, but if all you are ever going to do is shoot at paper targets in daylight while sitting at a bench, why spend massive amounts of cash? Find a solid reliable optic for a fraction of the price. One thing I have noticed is some folks will buy a higher dollar optic, then go all cheap on the mounting hardware and end up with things not being rock solid reliable. Your rifle and optic could be as accurate as a laser beam, but if that optic isn't mounted securely, you may not ever realize its full potential. Good quality does not always mean ultra expensive.

Just my thoughts

[JeepHammer]

It doesn't matter if it's bought or built to me...
The basics still apply to semi autos as bolt rifles.

This is actual old school GUN SMITHING, and not just assembling parts.
This will get you that sliky smooth PERFECT FIT,
Not just some +/- tolerance that is so popular today...

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1. TRUE RECEIVER.
What ever accepts the barrel and sights MUST be true to that barrel and optics.

First thing is to true the INSIDE OF THE TUBE on the receiver.
Straight line, evenly sized, the ONLY way to do this is with honing/lapping.

I see guys stuff boring bars in a receiver, and that's just NOT going to work,
Boring bars SIDE LOAD the receiver, so the internal cut is never true and rarely even.

Honing, lapping, or even reaming will produce a true tube in the receiver, and that is the ONLY way to do it.

2. BARREL FACE END OF THE RECEIVER.

AGAIN, the ONLY way to true the barrel face is to use the TRUE TUBE you just honed/lapped true.
That barrel face MUST be 90° to the tube.
NO EXCEPTIONS.

ANY MISALIGNMENT AT ALL will cock the barrel in the receiver, and the rifle optics/bore will NOT line up.

The same is true with receiver threads.
If they are not PRECISELY lined up with the bore in the receiver, the barrel will be cocked. PERIOD.

3. BARREL MATING FACE MUST BE TRUE WITH BORE.
It's MUCH easier when you true up the bore in a lathe and CUT the threads,
Using a die to cut threads in a second process virtually ensures the threads will NOT be true with the bore of the barrel.

Threading dies line up on the OUTSIDE of the barrel,
Which bores while straight, are NOT lined up with the outside profile of the barrel.
The bore is slightly offset in the barrel.

By lining up with the BORE, and cutting threads on the barrel, you get threads lined up with the BORE,
Not the outside profile.

This gives you a BORE that is directly lined up with the receiver...
And you aren't trying to 'Bend' the bullet into offset bore.

4. BOLT LAPPING INTO PLACE,
BOLT FACE TRUING/SQUARING.

This is pretty simple, if you have a lathe, you simply cut a plug with threads that match the receiver,

For bolt rifles, that's outside the plug,
For ARs, it resembles a chamber nut and the barrel nut holds it in place.

Use a spring, and a second bolt face size plug, Looks kind of like a 'Tack', head and shank in a 'T' shape.

Since these parts will be lathe turned, they will be square,
(why a gun smith needs a lathe)

With bolt stripped, fit the 'Tack' head into the bolt face where the cartridge would seat, put the spring on the 'Tack' and screw on the plug.

This applies spring pressure to bolt lugs via the bolt face.
You use the bolt face because that's where the cartridge will rest, and center pressure is CRUCIAL to getting lugs lapped in squarely.

First, simply use some lapping compound on the bolt lugs,
Work the bolt several times to the point of lock/unlock,
Trying NOT to fully unlock the bolt since the lapping compund will attack the square edges of the bolt locking lugs,
The bolt lugs will lap into place with the spring pressure keeping everything centered.

This will make for a SILKY SMOOTH bolt lock up, with the lugs having EQUAL PRESSURE on each,
This PRECISELY cuts the lugs to mesh with each other.

When you are SURE the bolt lugs are locking up with a PRECISE FIT,
Then with a FINE GRIT lapping compound,
Work the bolt at the break over point to full unlock a few times.

I usually wait until I'm using the very finest grit lapping compound, nearly a mirror finish, before I let the bolt fully unlock to give that silky smooth initial lock lug engagement.
Don't OVERWORK those corners or you will screw up the lug face lock up clearance on one end of the lugs...

Clean the bolt lugs,...
When you think they are 'Clean Enough', do it two more times.
Lapping compound likes to embed in the metal and it takes some effort to get it all out.

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Then apply some lapping compound to the bolt face where the 'Tack' head is and repeat.
(STRIPPED BOLT! You don't want to lap the extractor or ejector!)

If your 'Tack' shank sticks through the 'Plug' you can use a drill for this one,

Lap in the bolt face SQUARELY with the bore in the receiver you already made square/true.

STOP REMOVING MATERIAL WHEN THE LAPPING COMPOUND HAS CUT AWAY ANY HIGH SPOTS!
Don't take any more off the bolt face than is absolutely necessary.

Again, fine grit to polish up the now SQUARE bolt face!
It will look REALLY good, and work WONDERFULLY, just like it was intended to do in the first place before some high production place decided,
"Rough As A Cob & Out Of Square by some +/- tolerance was 'OK'".

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The reason you square the receiver is obvious,
The reason you square/lap the bolt/ bolt face is to make it square with the square receiver.

You CAN NOT set head space correctly with an out of square bolt.
The bolt has to come FIRST.
Anything removed from the bolt will open up head space,

So chamber reaming/honing has to wait until the receiver/bolt is done.

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5. CHAMBER GETS CUT WITH THE BARREL BORE STILL LINED UP CENTERED IN THE LATHE!

And ONLY AFTER the receiver is trued, and the bolt lugs lapped in,
The bolt face squared!
Can you set the chamber depth for head space.

CLOSED BOLT!
That bolt face MUST be square with the bore!
No two ways about it!

If that bolt face,
(the part that contacts the bottom of the case where the primer is),

Isn't DEAD SQUARE with the bore, the case will shift during firing.
You 'Rack' the case diagonally, making for uneven release of the bullet, a case pushing sideways on the bullet as it's trying to make it's way into the throat of the barrel.

All bad news...

BORE aligned dead center the lathe,
Then cut down for threads, adding threads if necessary,
Then you ROUGH IN the chamber...

Screw on the receiver/bolt, use a case dummy cut to EXACTLY the specifications for head spacing.
(If you buy one, it's called a 'Head Spacing Gauge', but it's just a dummy cut to fit EXACTLY SAAMI Specifications)

Screw on receiver with bolt,
See if the chamber closes SMOOTHLY with the head space dummy in place.

If it doesn't, trim the chamber just a little more,
Screw on the receiver, and try again,
Continue until the bolt JUST CLOSES...

Now, the guys that 'Cut & Forget' will raise a fuss,
Saying the bolt should close FREELY...

THIS IS GUN SMITH STUFF, NOT ASSEMBLE UNTIL IT 'WORKS'...

The idea here is,
You are going to HONE/POLISH the chamber.

The chamber reamer left chatter marks, scratches, ect.
So very slightly UNDER SIZE chamber is what you want.

NOW...
With some actual BRAND NEW SAAMI cases,
This is where it gets a little expensive...

Drill/Tap the cases through the primer flash hole.
Thread an extension onto the case.
Apply lapping compound grit to the ouside of the case,
And hone that chamber to remove scratches/chatter marks.

Change cases REGULARLY, the brass will wear faster than the steel chamber.
When you see a little polish coming up,
Clean and test the chamber again with receiver, bolt and head space gauge.

As you polish the last of the head space into the chamber, the gauge will slide in and the bolt will close silky smooth!

This is MUCH slower than just jamming the reamer in a little farther and calling it 'Done',
But then again, this is GUN SMITHING, not production assembly...

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6. This is some of that 'Gun Smithing' again that most guys simply won't do...

I buy TWO chamber reamers, identical or not...

One that has the EXACT SAAMI CASE specifications,

And a second that has the BARREL TO RIFLING FORCING CONE/RIFLING THROAT PROFILE I WANT.

The first gets the freebore/forcing cone ground off,
It cuts the CHAMBER CASE POCKET to exactly SAAMI specifications.

NOW, since I like to hand load my ammo,
And I shoot a lot of semi autos
(that have magazines the rounds MUST fit into and feed from mag to chamber)

I'm limited to a specific COAL lenght tht will fit/feed from those magazines.
(COAL, Cartridge Over All Length)

Since closing up Freebore will usually improve accuracy,
And so will some specific throat profiles that 'Squeeze' the bullet into the bore,
I like to cut freebore and throat profiles separate from the case pocket...

One reamer has the freebore/throat ground down so it's just the case pocket,
The second has the case pocket ground down and just the freebore & throat cutter are still in place and cutting.

This allows me to close up excessive freebore for my rounds that fit into the mags well.

Bolt rifle guys don't use a crimp, and will just leave the bullet loose in the case, and let the throat push the bullet back into the case.

Autoloader guys find the bullet pushed back ALL THE WAY into the case quite often if they don't use a crimp to keep a SPECIFIC COAL,
And that crimp prohibits letting the throat set the freebore to zero...

Setting the freebore to *About* Zero, (VERY short) is achieved by cutting the freebore shorter than 'SAMMI' specifications.

Again, this is a GUN SMITH thing, and the 'SPECIFICATIONS ARE SPECIFICATIONS!' guys are going to jump up and down...

But it WORKS to make a barrel more accurate.
Remember, that throat is going to move FORWARD as the rifle fires... Some call it compaction, some call it 'Erosion',
It's actually a combination of the two.

Metal compacts, the throat moves forward,
Burning powder and friction remove metal, the throat moves forward,

The throat moves forward UNEVENLY,
So 'Erosion' will slam into one side of the bullet before the other, deforming the bullet before it hits rifling.

Older barrels with perfectly good rifling are often tossed because of 'Throat Erosion',
When in fact, that chamber can be re-cut,
The barrel moved back a little with some extra threads,
The back trimmed off for head space,
And the rifle is shooting again in no time.

This would also be a good time to square things up, lap in receiver to proper size, lap in bolt lugs, square up the bolt face, ect. while it's pulled down to nuts and bolts, and you are putting the barrel in a lathe anyway to add threads...

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As you might have guessed,
I'm not big on 'Assemblers',
Gunsmiths that are willing to sign off on their work,
Add flourishes, make sure EVERYTHING IS PERFECT instead of just "Within Tolerance"...

A Gun Smith will take the time to build a rifle that last CENTURIES,
Functions FLAWLESSLY,

Not just a couple of seasons at some 'Competition',
or thrown together parts that go 'BANG' when the trigger is pulled (or yanked with modern triggers, you need a pry bar to get a release!).