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Old April 9, 2020, 07:35 PM   #1
TXAZ
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Why can't you make a Semi-auto as accurate as a Bolt action?

Simple question, there are some very precision built bolt action rifles that can shoot 1/2 MOA all day long, but it seems that few semi's that can get much below 1 MOA.

What would you have to do to build a semi that could get to 1/2 MOA (or better?)
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Old April 9, 2020, 11:36 PM   #2
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First,in the world I live in,the < 05 MOA "all day long" bolt gun is far easier to build with a keyboard than it is with tools.

I'm not saying t can't be done,but a lot of < 05 MOA "All Day Long" rifles don't pass the Missouri Test...."Show Me" at hashtag "Talk is cheap"

At least for most of us. Enough resources can get about anything done.

The rest of us might find / build one once in a while.

Semi-Auto? know of a Krieger barreled Armalite AR-10 T that shoots very well beside some very expensive long range bolt guns. I can't scientifically prove its a 0.XXX MOA rifle. I've seen shoot 300 yd groups I'd be grateful to get at 100 yds with an accurate bolt gun.

I'll concede a bolt gun can probably be more accurate,but with quality parts,an excellent barrel,and a free float forend,and a good assembler..

AR-10's and AR-15's usually shot very well. Most of the time,I'd say MOA or better at 100 yds . By "less" you might get a .75 or 5 MOA rifle. Maybe even better.

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Old April 10, 2020, 12:39 AM   #3
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What would you have to do to build a semi that could get to 1/2 MOA (or better?)
Probably design it for that from the ground up. Remember that accuracy is consistency. Rifle and ammo doing exactly the same thing, the same way, and the same amount, every time. The more parts involved, the more moving parts involved the larger the amount of variables, and the larger the number of variables, the greater number of them that can (and often do) lack the consistency needed in all things.

the DI guns, without a moving piston and op-rod have shown to be mechanically easier to get consistent than other designs, though that wasn't always the case. Lots of things have been learned and things changed, the "accurate AR" of today is more than a bit different from the rifle as originally made.

Consider how a well done "tuned" bolt action and ammo can fit each other, and how doing the same kind of thing to a semi might not be possible and still have it run semi-automatically.

Neck sized ammo, bullets loaded just off the lands (which might not fit in a magazine) things like that are tough to get in a semi that still runs reliably.

And, that's another point, with the modern AR being somewhat of an exception, about all other semis are either based on, or heavily influenced by military arms where the main focus is reliability over match level accuracy.

Semi auto rifles designed as sporting rifles (centerfire) are not good platforms for match rifles, there's simply too many design features that work against a "one hole group" rifle. Sometimes, the stars line up and you get unexpected accuracy from one, but its not something you can create on demand. (if it was, someone would be doing it)
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Old April 10, 2020, 03:27 AM   #4
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What would you have to do to build a semi that could get to 1/2 MOA (or better?)
Well, first off, most bolt action rifles are no better than most semi-auto rifles. Very few will consistently shoot 1 MOA. Sure, for 10 or so rounds they do, but then they start spreading the shots around. Same with semi-autos, few will shoot better than 1 MOA for very long. The weak links in any firearm are trigger and barrel, so let's talk about that.

Let's say I have a benchrest rifle that shoots 1/8 MOA. It has a $500 barrel, a $200 trigger, a $1000 action, and a $1000 scope. In matches it shoots less than .100" at 100 yds. Every part of that rifle is precision manufactured to very tight specifications. Ammo is assembled using only the best components.

And let's say I have a semi-auto rifle that shoots 1/8 MOA. It has the same $500 barrel, a $400 trigger, a billet upper and lower receiver, and the same $1000 scope. Everything is manufactured to the same specifications, and the ammo is assembled using only the best components. It will shoot very well indeed, but will probably not shoot as well as the bolt action, but not much worse.

Now let's do a parts count for the rifles. The bolt action will have maybe 20 parts. The semi-auto will have maybe 50 or 100 parts. So, more parts, more potential for inaccuracy. Let's look at the complexity of the machining required to make the action. Fairly simple machining for the bolt action, but fairly complex for the semi-auto. More complexity means more potential for inaccuracy.

Now, let's talk about the REAL weak link in most target rifles. The same people who complain that their rifle is not accurate can't shoot as well as the rifle has the potential to shoot, so how would they know the rifle isn't accurate to begin with?

Now, in real life, my bench rifle shoots about 1/8 MOA, and my target AR-15 shoots about 1/8 MOA, both hand held off the bench. Until this starts to limit my progress in any shooting sport, I am not going to blame the rifle.
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Old April 10, 2020, 05:13 AM   #5
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I agree with all the above. The semis are more complex and have more moving parts. More stuff moving around is going to have some effect. Let's also discuss ergonomics. I can take any one of my bolt rifles and pull it up to my cheek and it feels and points naturally. My ARs are like trying to hug a gun made of legos. That's not to say I haven't 'fitted' them to make the interfacing as comfortable as possible, but they are nothing like a bolt gun. Shooting an AR off a bench is a balance of trying to handle it to keep it precisely aimed and not manhandling it so much that I'm causing inaccuracy. The pistol grip is both a help and a hindrance in this aspect IMO.
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Old April 10, 2020, 05:17 AM   #6
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What does “all day long” actually mean to you? How long is that day? How many shots are you taking? What is your rate of fire? At what distance are you shooting?
Without definitive answers to these (and other) question, “all day long” is meaningless.
My Colt AR 15 has a “best group” of 1/2” (five consecutive shots at 100 yards, benched, iron sights). I did that once. Never tried again.
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my target AR-15 shoots about 1/8 MOA, both hand held off the bench.
You are shooting one hole groups (0.125” c to c) off your elbows with an AR15 (distance?).
Is that correct? Or am I misunderstanding?
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Old April 10, 2020, 05:39 AM   #7
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Bolt action--simpler mechanics. That's about it.
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Old April 10, 2020, 06:43 AM   #8
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In part an accurate firearm goes into battery the same for every shot. The alignment of the bolt and the cartridge to the chamber, and the alignment of the bullet to the chamber and the barrel are important. In a bolt action you can form the cartridge case to fit the chamber and single load the cartridges to avoid changing the position of the bullet in the case. In an auto loader you may need cases smaller than the chamber for reliable feeding, and the bullet may get slightly knocked out of position by the feed ramp. The bolt action has the potential to position the bullet more accurately with respect to the bore for each shot than does an autoloader. That consistency contributes to accuracy.
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Old April 10, 2020, 10:43 AM   #9
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OK,"Simpler Mechanics" or "Parts complexity" sound feasible

But if field strip an AR BCG vs a Rem 700,M-70,Savage,Ruger,etc,There isn't all that much difference in complexity.

Now what might influence accuracy is the mass of most bolt striker/mainspring/cocking piece assemblies vs the AR firing pin and hammer.

An AR lacks the complexity of a Rem Model 81 or Win 97.

And most of the parts,like the bolt release,mag catch,charging handle,dust cover, bolt assist really play no part n accuracy.

Get the co-ordinate measuring machine out and compare he blueprint check of a decent quality (Aero,for example...affordable,not exotic) upper/lower matched set and BCG

Competitively priced with a Rem 700

See which assembly will most precisely present the bolt face to a chamber. Slop,co-axiallity,etc.

Most bolt guns have some slop ,heat treat warpage,etc. There is a reason folks pay money to blueprint them.

Most bolt guns,except single shot bench rest guns,are a front receiver ring,a rear receiver ring,and a couple of rails. Then 4 screws hold the scope base.

Not really that rigid. I'd give the AR upper the advantage in keeping the scope and the barrel pointed the same direction.

As far s the dynamics of absorbing intial recoil...not talking about specialized bench guns...reciever recoil lug to stock,slabs on each side the mag box flex,etc. The straigt line recoil of the AR,probably better.

If we are comparing 8 to 12lb rifles you can carry for a walk,I don't think the bolts have a big advantage.Who builds 30 lb AR rail guns?

Ammo abuse during cycling? Well,either can be single loaded,and cycling from a bolt gun can abuse the ammo,same as a semi auto.They feed from a magazine.I'd say if the magazines and ammo are right,its possible for the semi auto to feed ammo that is not damaged.

I hesitate to make accuracy claims. Talk is cheap. Kreiger fitted the barrel to the Armalite AR-10T I mentioned.t hs a good trigger,eithr a Jewell or Gisselle,
and a 4.5-14 30mm Leupold Long Range on it.

Brother got some practice with it wearing out the Badger barrel Armalite built it with.It seems to shoot mostly ragged holes at 100 yds. Its a .308.

IMO it takes less skill and voodoo to assemble a formula AR that shoots < 1 MOA than it does Re-chasing threads,truing receivers,pillar,glass,or etc bedding...the gunsmithing of building an accurate bolt gun

Assembling off the shelf receiver,unmodified,I don't know that a Rem 700 or Savage or M-70 beat a quality AR.

Last edited by HiBC; April 10, 2020 at 10:55 AM.
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Old April 10, 2020, 03:26 PM   #10
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The first AR-15 I built was with no special tools. I was trying to go cheap and got the barrel off GunBroker, the seller promised it was from a "famous maker". I tightened the barrel nut with a pipe wrench, no torque specs, just tight, then tighter till the gas tube hole lined up.
First three shot group was a clover leaf about 3/8ths of an inch diameter. You can cover 5 shots with a dime. AR's that shoot under 1/2 MOA aren't that unusual.
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Old April 10, 2020, 04:08 PM   #11
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It's possible to build a MOA bolt gun and sell it for under $400. It is possible to build a semi-auto that is MOA, but it's going to cost more than $400. And it won't be as reliable. It's hard to build a semi with close tolerances and reliable functioning at the same time. It's just a lot easier to do that with a bolt gun

If your goal is under MOA then it just gets even harder and more expensive. I don't think you'll ever see a semi that can compete with the very best bolt guns. But for the average shooter the difference isn't that great.
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Old April 10, 2020, 06:24 PM   #12
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My F class AR is as accurate as my bolt action.
But with fast twist and long throat for heavy bullets, it is pretty much just a self cocking single shot. I haven't fired a magazine length round out of it since it got its 28" barrel.
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Old April 10, 2020, 06:44 PM   #13
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If you consider accuracy to be a result of consistency and perfect geometric alignment (concentricity, perpendicularity, even torque, rigidity etc.) of the following primary components: barrel, bolt face, bolt lugs, receiver lugs/barrel extension, and optic,

then look at the difference between what a semi-automatic and a bolt action must accomplish. A semi-automatic must have some type of gas assembly (more variables affecting the barrel) or some type of recoil delay assembly (affecting the bolt, barrel, or both). Even a DI gas gun has something interacting with the barrel which is just one more part which may have a variance after the stress of recoil normalizes and parts attempt to go back to their resting state.

Then it has the recoil spring pushing the bolt carrier assembly into battery, sometimes with bolt bounce. Does this happen exactly the same way every time?

Then you have to consider that if you machine your semi-automatic to extremely tight fits, you may not like the way it performs when there is the slightest change in its environment. Bolt actions too, but far less so.

Lock time is potentially a factor too if you believe that to have an effect, I believe it's less on many bolt action rifles, especially with match trigger and firing pin assemblies.

You can make a very accurate gun in either configuration, but I believe if equal attention to detail is paid, you could expect consistently the bolt action to be that much more accurate.

Theoretically speaking, a design resembling a single shot cannon with a sliding breech or a falling block action should be about the most accurate design considering the possible rigidity and tightness of fit.
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Old April 10, 2020, 07:28 PM   #14
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But if field strip an AR BCG vs a Rem 700,M-70,Savage,Ruger,etc,There isn't all that much difference in complexity.
How do you define "isn't all that much difference"??

Bolt body, extractor, ejector and their springs, and pins, and firing pin common to both, the bolt gun's bolt is also going to have the firing pin spring, and bolt shroud piece(s), where the AR is going to have the carrier, carrier key and screws, and the cam pin, bolt gas rings etc. Might not be many more parts, but what those parts DO is a lot more than the simpler bolt action.

Quote:
An AR lacks the complexity of a Rem Model 81 or Win 97.
I'll agree the AR isn't as complicated as many 100 year old + designs. But that kind of irrelevant to the topic under discussion. Don't know of anyone who's built a match rifle from a Rem 81 or a Winchester 97 SHOTGUN...

You might consider that the general accuracy of today's AR pattern rifles is the result of over a half century of constant development with an emphasis on making them more accurate.

That same "pressure" wasn't applied to bolt guns, which were and are closer to the practical maximum possible.

Make a comparison, between a 1964 AR15 and a 2014 AR15. Look at the barrel, handguards, manner of attachment etc, I consider the differences significant.
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Old April 10, 2020, 09:16 PM   #15
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In the NRL and PRS realm, you see both bolts and semis. Bolts are much more common and win a lot more. Semis _generally_ cost distinctly more for reasonably comparable precision.
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Old April 10, 2020, 11:48 PM   #16
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You are shooting one hole groups (0.125” c to c) off your elbows with an AR15 (distance?).
Is that correct? Or am I misunderstanding?
No, off of bags, but held to the shoulder and gripped so that I can operate the trigger. Not free recoil.
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Old April 11, 2020, 02:17 AM   #17
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Scorch: Thanks for clarifying. When I read “hand held”, I immediately thought of shooting off the elbows since there was no mention of bags. Impressive shooting.
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Old April 11, 2020, 04:06 AM   #18
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My F class AR is as accurate as my bolt action.
But with fast twist and long throat for heavy bullets, it is pretty much just a self cocking single shot. I haven't fired a magazine length round out of it since it got its 28" barrel.
They allow semi-autos in comps to be hand-fed?
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Old April 11, 2020, 07:23 AM   #19
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You can buy a Semi-auto that will shoot consistently under 0.5 inches with 5-round groups at 100 yards, but you'll have to pay big bucks for it.

I agree with all the posters who commented on how much easier it is to build a bolt action that will shoot accurately.
Most bolt actions that I have don't have the magazine O.A.L. limitations that come with most semi-automatics, especially ARs. I get my best accuracy when I load out to the jump that the barrel shoots best at.
I can't do that with my best and expensive AR unless I shoot single shot with a follower like Jim Watson indicates in post #12. My other ARs won't even come close.

I bought a Les Baer Super Varmint .223 1:8 twist in 2014 that was guaranteed to shoot 1/2 inch 5 round groups at 100 yards with factory ammo. I bought it new for $2,250.

The test groups that came with the rifle shot with Federal Premium Gold Medal Match factory ammo (Sierra 77 grain SMK Bullets) measured 0.126 and 0.074 using On Target software. Clearly the rifle was capable of what they claimed, the rest depends on the shooter.

My long-term 5 round group average (339 5-round groups) with factory ammo and hand load ammo with a variety of bullet weights and powders at 100 yards is 0.408.
That shows you that my set up and hold technique does not quite measure up to the solid fixture that Les Baer used.

But my top 25 5-round group average with the Les Baer's favorite hand load bullets and powders at 100 yards is 0.275. That just proves that even an accurate rifle doesn't shoot all bullet weights and powders equally.

My best results came when I loaded the 77 and 69 grain bullets out to fit the chamber and not the magazine but I had to use a single round follower, but that sort of defeated the purpose of an semi-auto AR platform.

I have 5 bolt action rifles that have long term 5-round group averages that are better than the Les Baer semi-auto (two of them cost less than $400 new in 2019, two cost under $700 new in 2013 and one cost $1,100 new in 2017). That would tend to confirm that you can build an accurate bolt action rifle a lot cheaper than a semi-auto.
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Old April 11, 2020, 07:53 AM   #20
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in rimfire land a lot of the 10/22 clones can do some pretty good groups at 50 yards. I have a Kidd that shoots one holers on a fairly consistent basis with CCI Std Vel and had a amazing group of .133 inches (.266 MOA) with high dollar Lapua
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Old April 11, 2020, 08:03 AM   #21
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This is a simpler question than most are answering, IMO.....

1) Case fit to chamber....precision bolt guns have case fit where the CBTD fit is within 0.0005” of the bolt not closing.....due to the weaker bolt closing force of a semi, you need 0.002-0.003” to be reliable.

2) Bedding.....the bedding of a precision rifle is rock solid. An AR Has some movement at one or both pins almost regardless of what you do to shim that out.

3) Neck Tension.....the most accurate bolt action guns have reduced neck tension....some BR guys go so loose as to seat it long and use bolt closing to push the bullet to final depth. I think most semi accurate folks use bushing dies to get down to 0.001”-0.002”. Where semi’s need 0.004” or more to just get the gun cycled.

4) Trigger....there are reliable 2oz bolt gun triggers. Semi’s seem to get unreliable under 2lbs...why. Semi’s need to disconnect. That creates more movement and more pull weight. While thiis is a fact, I’m not positive that a 2lb trigger can’t shoot bugholes.

All this said, I have reasonable expectations.....I expect hunting bolt rifles to shoot sub 1.5 moa and most shoot sub 1 moa groups with developed handloads from a rest at 100yds. I expect my AR’s over 16” to shoot under 2 moa with the same. 16” and shorter, 4moa. All are 5 shot groups and are repeatable I no wind days.
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Old April 11, 2020, 09:29 AM   #22
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They allow semi-autos in comps to be hand-fed?
Required in F class.
Which is slow fire at mid to long range. You have at least 20 minutes to fire 20 shots, plus time for sighters. And most shooters bang them off faster than that to try to stay in the same wind condition if it is not too fluky.
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Old April 11, 2020, 11:23 AM   #23
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Back in the days when rebuilt 7.62 NATO service rifle were used in military competition, the best tested under 4 inches at 600 yards when tested clamped in free recoiling accuracy cradle. That's with new, good quality cases.

Rebuilt bolt action match rifles tested the same way with handloads shot under 3 inches at 600.

Which explains why sometimes, M14NM, M1A or M1 versions produced better scores than bolt action rifles shot in 3 positions without artificial support F class and benchrest folks get to use
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Old April 11, 2020, 12:32 PM   #24
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You can buy a Semi-auto that will shoot consistently under 0.5 inches with 5-round groups at 100 yards, but you'll have to pay big bucks for it.
From whom???? And does it come with a written guarantee that it will put 5 shots under 0.5 inches at 100 yards???

IS there someone out there stating every single one of their production (or custom) rifles will do that, AND putting it in writing???
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Old April 11, 2020, 01:22 PM   #25
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deleat

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