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Old March 6, 2018, 08:20 AM   #1
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Armalite AR10 vs building a gun?

So I was looking around, and the idea of a .308 AR type rifle has been really growing on me.

That said I’m in a position that I may be able to buy an AR10 outright, or go and just buy the parts to put one together myself. However, my experience on what makes such a rifle accurate and what have you is beyond the scope of my knowledge. (Basic stuff that I’ve read is ensuring proper fit and finish as well as free floating the barrel among other things can help go towards accurizing the rifle)

As for the purpose of the rifle, I’d eventually like to see about entering long range shooting competitions or even just practice doing so on my own.

Does anyone have any suggestions or advice for either route, or perhaps better options out there if I decide to go with an already built rifle to build off of?

I’ve heard BCM is an excellent rifle manufacturer, but I don’t remember if they offer rifles in .308 or not.
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Old March 6, 2018, 09:34 AM   #2
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The barrel and developing a load for a particular barrel is the most important part when it comes to accuracy. Plus the shooter's ability, trigger, free float hand guard and glass are also a factor. Improper installation of the barrel and muzzle device can also affect accuracy. Only you can decide whether you're willing to invest in the time and tools needed to build an accurate AR10.
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Old March 6, 2018, 09:54 AM   #3
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Same advise I give everyone that wants to shoot long range, find a trainer/coach.
I've never seen anyone shoot long range CONSISTENTLY without rock solid fundamentals.
The simple truth is you need a coach to observe, find & correct faults before they become bad habits.

No one else at the top of any game/sport gets there without good coaching, I don't know why shooters think long range is any different.

A coach will spot bad fundamentals, correct you, and watch to make sure you correct your fundamentals. A coach will give you an understanding of what's happening, and give you a vocabulary to express what you are seeing/doing.

You can buy all the 'Whiz-Bang', 'High Tech' & 'Super-Duper' gadgets in the world, but none of that is going to correct or compensate for bad fundamentals, and you won't have the understanding or vocabulary to express anything you do notice.
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Old March 6, 2018, 10:30 AM   #4
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As for AR format and actual long range, it can be done, but it isn't cheap.
AR10 in .308 will shoot consistantly at 600 yds, while sometimes reaching out to 800 yds.
The only CONSISTANT 800-1,000 yard rifle I ever built was chambered in .300 WSM, and trust me, it wasn't cheap or easy.

It's a muzzle velocity thing, .308 simply isn't the fastest out of the muzzle, so it often goes 'Transonic' between 800-1,000 yds. That induces the bullet to wobble.
Short barrel bolt shooters have found this to be true, the M24 SWS the Army uses, even with 'Hot' (LR) 7.62x51 ammo still has the issue.
Semi-autos, and in particular the AR format, shoot a little slower at the muzzle further compounding the problem.
Velocity and twist rate in the barrel cover up a multitude of deficiency & sin...
(See AR15s with stupid fast barrel twist rates)

There is a LOT less that can go wrong with shooting a bolt rifle long range, I'd start there.
There are several offerings under $800 that will shoot 800 yds off the shelf to get the hang of long range before you spend a ton of money on stroking an AR10 to reach 800 yds.
Lots of moving parts that have to work PRECISELY for an AR to reach past 800 yds., not exactly the best learning platform...
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Old March 6, 2018, 10:44 AM   #5
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As far as build or buy... When it comes to Armalite, they have two versions, one that takes older m14/m1a mags, and one that takes the SR25 type mags, of which Magpul are a type of. If you go with Armalite, it's best to know which you are getting, as mag availability will be affected.

Most of the AR10 builds you see follow the DPMS specs, which have the largest options for parts compatibility. And most other ready built rifles will follow the DPMS pattern as well.

If you build, I would pick a single manufacturer, and stick with them for things like the receivers and parts kits. This will help ensure parts fit and work together properly... there is no "standard spec" for AR10s... Many may be using the DPMS pattern, but it's no garantee that mixing and matching different manufacturers will work out.

Mega Arms, Rainer, and Aero Precision make good receiver and parts kits.

Usually you can select a preferred barrel manufacturer and be fine. There are several manufacturers of good barrels.

The barrel is the heart of accuracy... Quality ammunition is it's moving force.

After selecting a good barrel, and getting other up to par components, then assembling the rifle following the standard established procedures... Then with the right skill set and ability, most can get a rifle that will shoot MOA or better.

Something like that will serve most shooters well enough.

If in the future, you want to do long range competition, you may find your skills hitting the limits of a basic build. Then you may need to see about building again, using all the little tricks and procedures to square up an action and get everything the best it can be.

There are companies that build like that for you as well... Expect to pay $4000 or more for that level of build... Or invest in the tooling required, and learn to do it yourself.

I would say, that until you hit a high proficiency, going those extra steps will not let you any noticable accuracy improvements. Most shooters can't hold simple moa accuracy with any consistency.

So in the end, it's up to you if you want to spend the effort to build, or just buy outright. Just know, that not all ready built rifles will manage moa or better accuracy, and I do not expect it, unless the manufacturer makes the claims that it can.

So, if you buy, and want moa accuracy, look to brands that make that claim.

If you go with another manufacturer, and even the best shooter with the best ammo can not get any better than 1.5in at 100yds, they are likely to tell you that it's in there accuracy spec, and if you want better, it's up to you to change the barrel, or whatever else is necessary to get the performance you want.
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Old March 6, 2018, 11:13 AM   #6
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The barrel is the heart of accuracy... Quality ammunition is it's moving force.

This should be tattooed on would-be builders & 'Long Range' shooters!

Spending $130 on a barrel & $400 on a 'Tacti-Cool' camo pattern coating!
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Old March 6, 2018, 11:54 AM   #7
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You have a unique outlook in this day & age where 'Style' trumps Substance.
When I tell a customer it takes $1,500 to get a rifle shooting 1,000 yards dead nut consistent, they freak out!
My time/machine tools/tooling & knowledge base is what makes the rifle... And I have to eat, pay bills & taxes, etc just like everyone else.
My shop rates are lower than most common machine shops, and they still freak out...

When someone with little or no skills comes in and wants a 'Long Range' rifle, I have 600 marked yards out back... 850 when the river isn't flooded (you can't shoot across water in my state).
I hand them an honest 1,000 yard shooter and see if they can hit anything at 500 or 600...
If they can't, I recommend a couple local coaches and the second freak out comes!
I don't have the patients or time to coach, but there are a couple local retired guys that do it cheap, and they are VERY effective, have open access to my home range so no range fees, ect.

Still the freakout!

Virtually no one will pay the $4,000 to $8,000 to get into a proven long range rifle, and they think the time of the guy that can take raw castings, barrel, BCG & trigger group, make that pile of parts fit together, then function together, then be CONSISTENT at long range isn't worth paying...

So they buy random parts, cut corners, hammer something together that goes 'Bang' thinking that $1,500 or $2,000 worth of parts is going to magically function at optimum performance...
They don't, the guy wasted a year and sells the rifle for something else and does it all over again...

The definition of insanity: Doing the same thing over & over again, expecting different results.
The common factor in all this is the GUY, same guy each time doing the same thing over & over...

When you can't drive the point home the Marines can teach any 'Joe' off the street to shoot quite well in under two weeks.
In 12 weeks the Marines can make any reasonably smart person consistantly hit targets at 1,000 yards or further.
That DI is your 'Coach' and he knows EXACTLY what he's doing, and his teaching methods are proven.

You are going to pay a gunsmith one way or another, either up front, or to assemble your parts correctly.
Just bite the bullet and do it...
The Marine Corps M40 has 220 man hours in inspections & fitting alone.
This discounts machine tools, tooling, inspection equipment, building space, power bills, etc.

Every rifle has a load developed specifically for that rifle and no other.
Each round of ammunition is hand built specifically for that rifle, and trust me, you won't tolerate the QC rejection rate when you hand load your own ammo, as many as 30% of bullets are rejected simply because they are over/under weight, out of round, over/under size, etc.

Keep in mind it takes 70 people in the rear to keep ONE Marine Corps Sniper in the field.
And the average 'Joe' wants to come along with $700 in his pocket and shoot like a Marine overnight...

I'm all for long range accuracy, I can build a rifle capable of long range accuracy but accuracy at the target ultimately depends on the dedication, discipline & education of the guy behind the rifle...
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Old March 6, 2018, 12:21 PM   #8
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I'm not sure if that's a good thing or a bad one.

Generally, I find that following the standard build procedures using quality parts, nets a rifle that has more than enough inherent accuracy for most shooters.

You can certainly get MOA or even sub MOA with good parts and following the build steps... But if you are wanting to get down into sub half MOA... Then you need to do more work... This is even more important on a rifle that is to be used past past 600-700yds or so.

Lapping and squaring parts, things like that... Most will never have the skill to notice the difference.

A difference in half an MOA is beyond most to see...
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Old March 6, 2018, 07:34 PM   #9
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Kimio asked:
Armalite AR10 vs building a gun?
For your first AR-10 style rifle, buy one already made.

As Marine6680 wrote in his post:

...there is no "standard spec" for AR10s... Many may be using the DPMS pattern, but it's no garantee that mixing and matching different manufacturers will work out.
Because of the absence of standard specifications for parts, building an AR-10 is not the same thing as building an AR-15 and you can easily invest $1,000 in a gun that won't work. And once you've put all those pieces together into a non-working gun and shot it enough to know it doesn't work, you have nobody to turn to fix the gun.
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Old March 6, 2018, 09:54 PM   #10
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Personally, I’ve no qualms about practicing. I agree that the gun is only as accurate as the shooter. Seeing as I’m a novice at long distance shooter I’d rather start off with a good foundation rifle and work up if need be.

It sounds like buying a solid pre-built rifle would be the better option for someone like me? The coaching thing is a great idea, I’ll just have to figure out if there are any good ones that I can go to in my area.
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Old March 6, 2018, 09:59 PM   #11
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The more moving parts you add to a rifle, the harder it will be to make it accurate. Starting an "accuracy build" with a semi-auto platform is akin to building a house on a boat in the water. It can be done but will be more difficult.
I have some very accurate AR 15 type rifles so it's not that difficult to build a reasonably accurate gas semi-auto. Building one meant for extreme range is a different task(and more expensive). Building such from parts which may not be made to a single set of specifications makes it even more difficult.
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Old March 7, 2018, 09:40 AM   #12
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The best advice for a novice builder is to get upper, lower & BCG from the same maker.
Some uppers won't accept other makers carrier, and upper/lower fitment is a challenge at best when you play mix & match. Some just flat won't fit together, period.

Buy as much barrel as you can afford!
No such thing as a hyper accurate $130 barrel... The best gunsmith/handloader in the world can't help you when the barrel is crap.
No one can put metal back into a barrel, once it's gouged out, the barrel is done...

As for a GUNSMITH building a rifle...
That 'Gunsmith' SHOULD be building for a one hole shooter!
To the best of his/her ability EVERY TIME.

If you take the mindset you are going to build a 3 MOA rifle, it's probably going to turn out a 5 MOA rifle or worse.
Since we aren't the government with unlimited resources, sometimes we have to compromise, but NEVER set out to be mediocre at best.

This is the part that kills me, and I see it all the time,
'Gunsmith' that doesn't have a flat bed to do setup on, doesn't have centers & dial indicator to check for concentric & true, etc.
Doesn't even have the most basic & inexpensive tools to quality check parts before they are screwed together!
An armorer's tool & hammer DOES NOT make you a gunsmith!

This is simple, basic physics.
If the front of the upper receiver IS NOT square with the BCG bore (and virtually NONE are) then the barrel/bolt has ZERO chance of locking up square together.
Forget the misalignment of sights, wear on the upper from the BCG side loading the upper,
This just plain IS NOT SAFE!
When bolt lugs can not lock up solidly on the chamber lugs, you are concentrating the firing forces on one or two lugs way overloading them! NOT SAFE!

When you don't face off the upper receiver SQUARE with the BCG bore, the BCG/Barrel can not lock up square. Period.
When you don't hang the barrel between centers and check the changer nut flange for square, you have no idea if the barrel/bolt can lock up correctly.
This takes a machinist flat table, centers & fixtures, & a dial indicator.
If you don't have these things, you simply can not insure the locking lugs are engaged fully.

Forget accuracy, how about NOT blowing the upper apart in your face!?
The worst part is, it's not going to come apart right away, it will fail at random.

Without a square bolt face, you have little chance at accuracy since you are essentially bending every case you fire through the rifle.
Without checking for true/square, receiver mounted sights will never line directly up with barrel mounted sights, and receiver mounted optics will ALWAYS be cocked at an angle to the bore centerline.
So much for your fancy, expensive optics!

It's real simple, but I see so few that verify they are working with correct parts out of the box, then claiming the rifle 'Can't' shoot sub MOA...
Just because their particular rifle won't, doesn't mean all won't...

I use a fixture, taking the human element out of firing.
Shoot 3 groups before, shoot 3 groups after, proving the rifle got more 'Inherently Accurate' after I worked on it...
Why people think the same things that help bolt rifles don't work on semi-autos is baffling to me.
Squaring the barrel with receiver, squaring bolt face with chamber/bore, proper chamberings, lapping bore, lapping locking lugs, etc.
All this contributes to your accuracy potential, and ZERO of it is difficult, the basic tools & fixtures are commercially available, but a guy building ONE rifle isn't going to know about or buy these basic tools, or know how to use them.
This is where a gunsmith comes in...

Last edited by JeepHammer; March 7, 2018 at 09:45 AM.
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Old March 7, 2018, 10:41 AM   #13
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I have a Ruger SR 762. I shoot a federal gold medal match clone load out of it using 175 gr Sierra BTHP's. The gun with the trigger upgrades, PRS stock and brake comes out to about $2,100.

Then, I have a Vortex Razor scope on it. It is an honest MOA rifle which is pretty outstanding for an AR-10. But 1000 yards isn't going to happen in that gun. it has a 16.125" barrel, and even if I went up to 20 or 24 I would be hard pressed to stay super sonic out to 1,000.

I also shoot F-Class open, 1k yards and 600 yards. The F/TR class at 1,000 yards uses .308, but they are using 28-32" barrels. A 24" barrel could stay super sonic to 1,000 yards but you are going to have to be very careful about bullet selection and they will need to be loaded very hot....especially in a gas gun.
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Old March 8, 2018, 02:26 AM   #14
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I've built quite a few xx308 AR's as well as AR15's--I can attest to what jeephammer says is true--and is made a little harder in the the xx308 platform due to the tendency of most manufacturers to make their receivers and parts play best with their own stuff. I'm not as precise as jeephammer is in my assembly and could stand some improvement there.

Another thing that I've found equally challenging to precision in assembly is tuning and balancing the gas system. Shooting the bigger cartridges and with a wider range of charge and bullet weights is a real balancing act on getting functional and accurate gas cycling, dwell timing and pressure balancing within the gun.

IMO--a truly good build is one that not only shoots reliably and consistently accurate--but one that minimizes stress on both the gun itself as well as the shooter. I've also noticed a really good build will eject brass that is virtually damage-free.

PS--I just received my PTG 308 receiver lapping tool--they aren't even made anymore and have to be custom-ordered.
I screw things up--so you don't have to.

Last edited by stagpanther; March 8, 2018 at 08:09 AM.
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Old March 8, 2018, 08:08 PM   #15
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It's a quirk of the manufacturing & coating process.
The front threads of the upper (barrel nut threads) are often as not rolled into the aluminum.
Rolled threads are stronger, die cut threads leave issues also and let's face it, not many of us pull the threads off the upper when tightening the barrel nut, so I don't sweat it either way.

The issue is, either way it deforms the front face of the upper where the barrel nut seats, cocking the barrel no matter what you do.
The 'Fix' is to face this surface off SQUARE with the upper BCG bore.
A self piloting tool, something that pilots off the BCG bore, with a square face to lap off the front of the threaded area works fine, and you can do this by hand or with a hand drill motor turning the tool.

If you have the guide bar measured, and it's appropriate for the BCG bore, a little lapping compound on the BCG surface removes/polishes the BCG bore.
You would not believe how many BCG bores are undersize because of the coatings/finishes.
Sizing/slicking up that BCG bore will save you a bunch of problems/issues!
With the correct pilot/tool you get two for one, BCG sized/polished, and the front face of the upper receiver lapped square with the bore.

Doesn't matter what the outside profile of the receiver is doing, that BCG MUST line up with barrel bore or you simply build in problems from the start.

The other thing I find is chamber nuts are mostly lathe turned/cut so they are mostly square...
But lesser barrel makers DO NOT cut the barrel threads on a lathe, and I have no idea why.
Lathe cut threads, barrel BORE between centers, the threads will come out concentric with the bore and centered on the bore.

When they force the barrel blank into a die cutting machine, the threads NEVER come out concentric/centered, so the chamber nut screwed on cocked to the barrel bore.

To check for this, it's simple to set up pointed centers on a flat rail mount.
Simply put the barrel between the pointed centers, set up a dial indicator and check to see if the barrel nut flange 'Wobbles' as the barrel is rotated on the centers.
If it passes, the barrel threads were lathe cut, if the stop flange wobbles, time to straighten threads, which usually means a custom, undersized chamber nut that most guys can't produce...

Most people don't believe what these manufacturers try to get away with!
It's buyer beware out there...
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Old March 8, 2018, 08:32 PM   #16
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This is something thrown together at a friend's house, where I didn't have access to my head mill and it's dead flat table.

It's a chunk of heavy 90* heavy angle iron,
Left over optics mounts & rings,
A set of centers, intended for optics ring alignment,
And a dial indicator.

On the set of centers I use at home, the center I use in the chamber is cut to fit into the chamber and actually pilot on the bore.
That takes a lathe to cut the long pilot with the dummy cartridge/pilot end, the only custom part of this.

Common parts available at Midway, Brownells, etc for cheap.
Ring mounts, rings, centers & a heavy chunk of angle iron.
The only warning here is to get Weaver or picatinny rail that are FLAT and the same height.


This shows/explains what you are looking at/for.


This shows the lapping guide/tool used on the uppers so no lathe is required.
Notice the uppers, one lapped, one not. Nearly .125" had to be removed to get this upper square with BCG bore, which means the barrel had ZERO chance to align with the BCG...
This is quite common, like 85-90% common, virtually all uppers cock the barrel sideways.

Once square, shims are commonly available to get your chamber lockup/stroke & gas tube where it should be. Shims won't work until the face is square.

This is shortly into the lapping process, the shiny area shows you the 'High' side, this MUST be removed if you ever hope to get a barrel square/true with upper receiver, it's an absloute MUST.
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Old March 8, 2018, 08:39 PM   #17
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You would not believe how many BCG bores are undersize because of the coatings/finishes.
And I thought I was the only one driven nuts by this!
I screw things up--so you don't have to.
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