Semi Auto vs. Bolt Action for precision long range shooting

Rockrivr1

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So my question basically is can you get the same precision with a Semi Auto as you can with a Bolt Action. As I've posted in a previous thread I'm about to pull the trigger on a MPA BA PMR Pro rifle II for some long range shooting. I've been asked by a couple people why I don't get an upper for my AR-10 patter rifle and use that instead for longer range shots. I was always under the impression that Semi Autos were not as accurate and precise as a bolt action. I was told that was old thinking and not the case with today's modern Semi Auto rifles.

So I'm asking the NES brain trust. Can I get the same accuracy and precision with a Semi Auto AR-10 pattern rifle that I'd get out of a quality Bolt Action. For reference the AR-10 type is from Rock River Arms and would be their Predator HP Upper in 6.5 Creedmoor. Either rifle will have the same quality glass.
 
i believe there was a Bench rest guy, who set a record with an MSR, a few years back. his idea was to send the rounds quickly as the environment (wind, etc) would be the same for the whole string, vs normal bench rest shooting. i had a buddy who built a sub 1/2 moa 224 valkrye on that theory. i also have a sub moa JP upper that once in a while in my hands, will be under 1/2 moa.

i think inherently bolt is more accurate, but MSR can get pretty close.
 
They’re getting close enough to where the vast majority of us won’t be able to appreciate the difference in accuracy on any practical level. I’m not someone who has the skill to tell the difference anyway. So at this point I’d go with a semi.

I would go bolt for hunting though. And not because of accuracy, but because of weight and handling in the woods.
 
It’s possible to get an equally precise semi auto, but it will be more work.

In most semi autos, there is more possible bolt lockup fluctuation than with a bolt gun. JP and some other companies make bolt carriers for ARs that are a little beefier to minimize this. It is a small factor, but if you’re looking for consistent sub-half MOA, then it becomes a real factor.

For me, personally, getting 3/4-1 MOA from a semi auto is totally fine for all my use cases. I don’t need 1/2 MOA.

A benefit of semis that I like is with imbalanced support. It is easier to keep a semi on target vs shifting the weight while cycling the bolt.

But, aside from utmost mechanical precision, bolt guns do have the benefit of supporting a much larger range of cartridge pressures. They can run subs of various cartridges no problem. And possibly more importantly, they can push higher pressures, leading to faster muzzle velocities and therefore a shorter time of flight, flatter trajectory, and less wind drift. Which means better real world accuracy and hit probability, not just mechanical precision.
 
I thought bolt was better because it contained the gasses in the chamber/barrel etc... or something like that.
I think the theory is that with semi-auto, a teeny bit of gas is used for cycling, which takes away from bullet velocity. With bolt, 100% of the gas is used to send the bullet. I’m no expert, but I doubt the difference is significant at all. Maybe by the time the semi auto gas is used for cycling, the bullet has already reached max velocity.
 
i believe there was a Bench rest guy, who set a record with an MSR, a few years back. his idea was to send the rounds quickly as the environment (wind, etc) would be the same for the whole string, vs normal bench rest shooting. i had a buddy who built a sub 1/2 moa 224 valkrye on that theory. i also have a sub moa JP upper that once in a while in my hands, will be under 1/2 moa.

i think inherently bolt is more accurate, but MSR can get pretty close.
@Rockrivr1 , my experience is almost exactly as above. I built an Aero M5 in 6.5 CM with a Ballistic Advantage Premium barrel, JP BCG, Geissele SSAE trigger, and other JP components. It shoots at worst about .7 MOA and averages below half MOA with careful loads and careful shooting on my part. I have a thread on it somewhere. More than good enough for me.

I have shot a couple 1/4 MOA groups and even one group at ~.12", but no way can I do that consistently.
 
I think the theory is that with semi-auto, a teeny bit of gas is used for cycling, which takes away from bullet velocity. With bolt, 100% of the gas is used to send the bullet. I’m no expert, but I doubt the difference is significant at all. Maybe by the time the semi auto gas is used for cycling, the bullet has already reached max velocity.
I think there's more weight to the idea that the action cycles during the firing cycle. That means mechanical movements in the firearm can cause the system to deflect before the bullet leaves the muzzle.

This seems to have been more true with older designs. Modern firearms, especially the Stoner design, eliminate a lot of that.
 
I think there's more weight to the idea that the action cycles during the firing cycle. That means mechanical movements in the firearm can cause the system to deflect before the bullet leaves the muzzle.
Wouldn't a similar theory apply to a bolt gun with a 22" barrel? Will the bullet leave before the recoil kicks in?
 
Wouldn't a similar theory apply to a bolt gun with a 22" barrel? Will the bullet leave before the recoil kicks in?
Recoil is different.

In a semi, the action starts moving. This movement moves the firearm. Sometimes it moves the barrel itself (e.g., long recoil, browning tilt, etc.) while in others it might just shake things around.

n a manual action, the firearm is (considered) rigid until the shot completes, then the user can move whatever they want and it doesn't matter until the next shot.
 
Short answer no go with bolt gun it’ll be alot less stressful. There’s a reason why there are hardly no gassers shooting the long range stuff.

Way too many moving parts and tolerance issues to deal with in a gasser on top of them just being harder to shoot in general.
 
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Short answer no go with bolt gun it’ll be alot less stressful. There’s a reason why there are hardly no gassers shooting the long range stuff.

Way too many moving parts and tolerance issues to deal with in a gasser on top of them just being harder to shoot in general.
I don't shoot PRS but have a few friends that do. I don't think any of the PRS guys shoot semi-autos?
 
A bolt action by design removes some potential accuracy robbing variables. Primarily the S/A 2pc upper/lower configuration. Not an issue at short range, but reaching out to long range the minor design flaws can be more pronounced. You look closely at custom F open benchrest rigs they are simple, minimal free moving components and HEAVY.
 
I don't shoot PRS but have a few friends that do. I don't think any of the PRS guys shoot semi-autos?
There were a number (15 out of 75 total entrants) of semi autos at the match I went to this summer, me included. But none were competitive with the top spots.

The top semi auto was #16/75 with 84% of the score of #1, and 90.5% of the score of #2. The scores were all really close (except #1 who had a crazy 4 point lead over #2) and there were plenty of bolt guns below various semi autos.

So, the semi autos did some really incredible performance, and did things that people in the 20th and early 21st century would have thought were crazy. But the bolt guns can still provide edges.

Another factor I forgot to mention is more chambering options. It seemed like all the top shooters were shooting 6 GT. You aren’t going to be shooting that from a semi auto at the moment.
 
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can you get the same precision with a Semi Auto as you can with a Bolt Action
i would think a common consensus is - it is way simpler to accomplish great precision from a bolt action than a semi.
a perfectly fine built semi, with a custom fit bolt and minimal possible tolerances - from the engineering perspective it is all possible, but, is it same easy as a from a custom top tier bolt action? probably not. nor would i see a purpose of a such extremity for a semi.
 
Typically when i go with my savage 12 FTR 308 precision target bolt action up against a precision barreled accurized 7.62 AR platform at 600 yds ill shoot a 10, my s/a buddy will shoot a 9. I score an X my buddy will score a 10 (shooter proficiency being equal) Match barreled AR's can exhibit excellent accuracy out to midrange, but a sa typically is just a tad less accurate than a bolt .
 
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I don't think the reciprocating parts in a semi move appreciably while the bullet is in the barrel. Think about it, a 55-77 grain bullet is 1/100th the mass of the BCG, buffer weight and 1/2 the buffer spring, plus the bullet is half way down the barrel by the time it hits the gas port. The gas system does affect barrel whip, even if it's just a tube. It's not really a "free float" barrel in a semi. Also, if the gas system is a different material from the barrel (like, say, a SS gas tube with a 4150 barrel in an AR) then you get some differential thermal expansion as the gun heats up. There is also a difference in wall thickness, so the gas tube will get up to temp faster. Does this matter practically? Probably not much, but if you're going for maximum accuracy it would make a difference I suspect.
 
Can a semi auto shoot well and keep up with bolt guns? Sure as certain distances.

But for consistency at ELR then I think bolt is still the way to go.
 
So my question basically is can you get the same precision with a Semi Auto as you can with a Bolt Action.
as long as there have been bolt actions and semi auto's, this question has been discussed if you can get at least 2 shooters to sit together and talk guns. sort of like that perennial question that was the talk of gun clubs everywhere when i started shooting....what cartridge is best for all north american game animals....270 or 30-06. mr. @Rockrivr1, you made me smile thinking of the good times gone by. enjoy the discussion, guys.
 
I thought bolt was better because it contained the gasses in the chamber/barrel etc... or something like that.
I thought it was because the bolt always locks the same where a semi might not be perfect.

Or something like that.

OP, just get a bolt action. How much accuracy do you want? 1/8 MOA or or 1" MOA?
 
Along with the extra moving parts in a semi-auto, I've often thought that their accuracy could also be affected by slight bullet deformation when the semi-auto cycles and chambers the next round. It may be miniscule, but I've examined some unfired cycled/chambered cartridges and have noticed that they can get scrapes along the bullet from rubbing against the chamber opening.
 
There were a number (15 out of 75 total entrants) of semi autos at the match I went to this summer, me included. But none were competitive with the top spots.

The top semi auto was #16/75 with 84% of the score of #1, and 90.5% of the score of #2. The scores were all really close (except #1 who had a crazy 4 point lead over #2) and there were plenty of bolt guns below various semi autos.

So, the semi autos did some really incredible performance, and did things that people in the 20th and early 21st century would have thought were crazy. But the bolt guns can still provide edges.

Another factor I forgot to mention is more chambering options. It seemed like all the top shooters were shooting 6 GT. You aren’t going to be shooting that from a semi auto at the moment.
Which match was this? I just looked back through the match scores that I attended and out of 7 1-day matches there were a total of 3 gas guns between them.

If I remember correctly the OP wants to dable with PRS and if that’s the case either run an AR u have to get your feet wet or just bite the bullet and start with a bolt gun.

Either way if you stay in the game you will end up with a bolt gun. 😊
 
a question for the benchrest crowd...
when both bergara and the 6 dasher rig from MPA - both pretty, well, budget builds - give me an 1 inch group at 300 yards - it is a pleasure.
both guns are capable of that if loads are good and my hands do not shake/flinch. none of my ARs can reproduce such groups like that, it is just a fact.
 
Along with the extra moving parts in a semi-auto, I've often thought that their accuracy could also be affected by slight bullet deformation when the semi-auto cycles and chambers the next round. It may be miniscule, but I've examined some unfired cycled/chambered cartridges and have noticed that they can get scrapes along the bullet from rubbing against the chamber opening.
This can be minimized via a well matched and polished receiver to barrel extension junction.
 
Which match was this? I just looked back through the match scores that I attended and out of 7 1-day matches there were a total of 3 gas guns between them.

If I remember correctly the OP wants to dable with PRS and if that’s the case either run an AR u have to get your feet wet or just bite the bullet and start with a bolt gun.

Either way if you stay in the game you will end up with a bolt gun. 😊
August Granby, MA
 
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