The semi-auto,,,,,,Myth?

[K191145]

Okay, I heard some guy on a show about snipers, and i've heard it before that bolt actions are more accurate because a semi-auto's action is moving as the bullet is traveling down the barrel thus moving the rifle. Really? Can anyone time the bullet from the time the primer is ignited, igniting the powder pushing the bullet out of the case, traveling through the barrel and exit the muzzle? I'm not a ballistics expert or reloader but i'm pretty sure it's pretty darn fast, I mean I can see actions cycling with my naked eye. And what about gas operated rifles like an AK that has the gas port to assist the action near the muzzle? I may be wrong but it's just hard to imagine that the action on a semi-auto has much effect, or is actually moving before the bullet exits the muzzle.

Now could it be that many semi's have a looser lockup than some bolt rifles and maybe there is a little movement? Anyway, i'm just asking those who know alot more about that than me, it's just hard for me to imagine that the action itself has alot to do with accuracy on a semi. I do know there's some pretty accurate semi's I have seen like M1A National Match which does have tighter tolerances and a few others.

[mikegideon]

Ain't shit happening until the bullet passes the gas block. Fact is, bolt actions can have much tighter mechanical tolerances, and stronger bolts. BOTH have travelling mechanical distortions along the barrel from the discharge of the round, and both are most accurate when the rate of change of mechanical distortion is least at the end of the barrel when the bullet leaves the barrel.

 

Check out the Art of the Precision Rifle. Todd Hodnett says both types are capable of long range sniper service. And, there ain't many folks more qualified to make that statement. FWIW, Todd's goto personal rifle was an Accuracy International bolt gun. 

[mikegideon]

Here's a 308 load that I whipped up in Quickload. Note that it's slower than a .223, even with the 20 inch barrel. The bullet is out the barrel in right at a millisecond.

 

[173rdABN]

I'm going to tag this for later. Don't want to type a lot so late on my cell.

Quick note. Engineering and technology has come a long way in the recent years of gas gun platforms for long range. Before, a gas guns just couldn't come near keeping up with a bolt gun. Now, it's right at its back door. Think of harmonics alone. A gas gun has moving parts, no matter how you look at it, more so than a bolt gun. You might not think the bolt moves or does anything tell the gas hits the gas block and blows back to the key, but that bolt moves and it's enough to add to the list of other moving parts creating more harmonics. And with a suppressor that bolts darn near unlocked or is unlocked before gas gets back to the key on the carrier. It's called premature ejection. Awesome name, and fitting, I know. Bolt guns have less moving parts, tighter tolerances, and are inherently more accurate because of this. Again, think harmonics again.

At my last sniper match in Ga most people were running gas guns because they can keep up to bolt guns at 800 and in. But when you start pushing past that, a bolt gun just can't be beat. Hence why I run one and my gas gun almost never sees any action.

I also, like Todd, use an AI as my personal go to long range gun. And there's obvious reasons why that gun and platform are a favorite.

[mikegideon]

Yep. You gotta have enough slop to let the action cycle on a gas gun. If I had an AI, I probably wouldn't go out with anything else either.

[K191145]

I can see a loose tolerance moving a fraction of a fraction of a millimeter, they way this guy was talking on the show, he made it seem that the action was actually cycling, bolt handle retracting before the bullet leaves the muzzle. I know that bolt lugs on a bolt action lock up tighter and I can see a tiny movement in the bolt on a semi which could cause enough movement to effect accuracy, it wouldn't take much.

So harmonics is any movement of any part of the gun when fired? I always thought it had to do with barrel flexing and why people cork between the barrel and stock, or have a free floating stock.

TGO is a great place to learn.

[K191145]

Ain't #### happening until the bullet passes the gas block. Fact is, bolt actions can have much tighter mechanical tolerances, and stronger bolts. BOTH have travelling mechanical distortions along the barrel from the discharge of the round, and both are most accurate when the rate of change of mechanical distortion is least at the end of the barrel when the bullet leaves the barrel.

 

Check out the Art of the Precision Rifle. Todd Hodnett says both types are capable of long range sniper service. And, there ain't many folks more qualified to make that statement. FWIW, Todd's goto personal rifle was an Accuracy International bolt gun. 

 

I have to check that out, I see it's about $50 from Amazon for a set of 5 DVD's. I've been interested lately in doing some long range accuracy shooting. First thing is to get a "good" bolt action, again.

Years ago I bought an off the shelf Remington 700 ADL in 30-06, their bargin model and an inexpensive Simmons AETEC 2.8-10X44 scope. This was a deer rifle setup, by no means a competition setup. Still though, even with an inexpensive rifle and scope it was pretty accurate with it's favorite ammo which was Winchester Partitution Gold 150 grain. These were nylon coated bullets at the time, don't know if they still make them. At the Cheatham range I was limited to 100 yards which is nothing really but with that setup and ammo I had many groups of 3 with all holes touching, from a bench rest of course. I would have loved to see what I could do at longer ranges, even being a cheap rifle and scope I was more accurate with that than any rifle I have ever fired and I loved to shoot it because of that. I sold it a few years later because I was tight for some money then and planed to buy a nicer rifle and scope when I could afford it but never did.

[mikegideon]

I have to check that out, I see it's about $50 from Amazon for a set of 5 DVD's. I've been interested lately in doing some long range accuracy shooting. First thing is to get a "good" bolt action, again.

Years ago I bought an off the shelf Remington 700 ADL in 30-06, their bargin model and an inexpensive Simmons AETEC 2.8-10X44 scope. This was a deer rifle setup, by no means a competition setup. Still though, even with an inexpensive rifle and scope it was pretty accurate with it's favorite ammo which was Winchester Partitution Gold 150 grain. These were nylon coated bullets at the time, don't know if they still make them. At the Cheatham range I was limited to 100 yards which is nothing really but with that setup and ammo I had many groups of 3 with all holes touching, from a bench rest of course. I would have loved to see what I could do at longer ranges, even being a cheap rifle and scope I was more accurate with that than any rifle I have ever fired and I loved to shoot it because of that. I sold it a few years later because I was tight for some money then and planed to buy a nicer rifle and scope when I could afford it but never did.

 

I have it, and haven't been thru the whole thing. First thing you will notice, though, is that somew of the guys are shooting gas guns.

[mikegideon]

I can see a loose tolerance moving a fraction of a fraction of a millimeter, they way this guy was talking on the show, he made it seem that the action was actually cycling, bolt handle retracting before the bullet leaves the muzzle. I know that bolt lugs on a bolt action lock up tighter and I can see a tiny movement in the bolt on a semi which could cause enough movement to effect accuracy, it wouldn't take much.

So harmonics is any movement of any part of the gun when fired? I always thought it had to do with barrel flexing and why people cork between the barrel and stock, or have a free floating stock.

TGO is a great place to learn.

 

Harmonics, technically, is any multiple of a fundamental frequency. It gets abused some.

 

Here's some light reading...

 

http://www.the-long-family.com/optimal%20barrel%20time.htm

http://www.varmintal.com/abat85.htm

http://www.varmintal.com/abolt.htm

http://www.varmintal.com/atune.htm

[Caster]

Ronnie Barrett would vehemently disagree with this myth.

[Jonnin]

its less expensive and easier to make a very accurate bolt gun, for sure.  More moving parts makes accuracy more difficult, period.  It depends on the shot in question some too... you don't need rapid fire for a 3 mile shot, but if you are picking targets off at 500 - 1000 yards, which is *still* the vast majority of shots from what I have read/studied/heard (including sitting next to an ex marine sniper for a decade at work, sadly no longer here but I got him to talk a little over the years).  

 

Lets put in pistol terms.   It takes $5000 or so (much of it hand fitting) to make a match grade competition level 1911 that can put all the bullets in the same hole at 50 yards without having malfunctions caused by extra tight tolerances.   It takes handloaded ammo that is just - so to cycle and produce the desired groups.   It would not surprise me at all to see the same results from a $1500 mass produced quality revolver out of the box, using a wider variety of ammo (possibly including some of the better consistency factory stuff).  The same is true for rifles.  A pretty darn good bolt gun can hit 1k yard targets with a variety of ammo without breaking a sweat.   A 308 auto that can do that would finance 3 or 4 of the bolt guns,  even as many as 10 of them if you took away the out of the box requirement and instead made some bubba hack job milsurps with new barrels.   Heck, pretty sure my 1909 argy would get close to it if I had a scope on it.

 

 

Engineering, materials, knowledge, everything is there to do it.  If you throw enough $$ at the gun, you can make it accurate to the range of the projectile fired.   But the bolt gun can do it cheaper.  

Edited April 16, 2015 by Jonnin

[nightrunner]

Ronnie Barrett would vehemently disagree with this myth.

His M95 and M99 are considerably more accurate than his M82.

[173rdABN]

His M95 and M99 are considerably more accurate than his M82.

His m107 sucks. No one I know in my community likes it. At best it's a minute and a half gun. And it sucks.

[Johnny Rotten]

His M95 and M99 are considerably more accurate than his M82.

 

Maybe not.

edit, the video says its a 107 its really a 82a1

 

https://www.youtube.com/watch?v=u3BUnHiv6AA

Edited April 17, 2015 by Johnny Rotten

[K191145]

I've heard some good things about some of the M1A custom models, how are they compared to other semi's?

[173rdABN]

I've heard some good things about some of the M1A custom models, how are they compared to other semi's?

We had m21's in Afghanistan and they were decent at best. Ar308's are much better IMHO if you were to choose between the two.

[K191145]

We had m21's in Afghanistan and they were decent at best. Ar308's are much better IMHO if you were to choose between the two.

 

I've been watching some video's on the Ruger SR 7.62, I've heard it's pretty accurate even being a gas/piston rifle and also reliable but you may have to change the gas setting for certain ammo. What about the piston AR's?

[Ted S.]

Preference, perhaps.

[Johnny Rotten]

I've been watching some video's on the Ruger SR 7.62, I've heard it's pretty accurate even being a gas/piston rifle and also reliable but you may have to change the gas setting for certain ammo. What about the piston AR's?

 

Look at a Colt LE901, this is my semi precision rig.. 

Few cool things about this gun.

1. Battle rifle.

2. There is an magwell adapter block that allows you to install 556 uppers.

3. You could SBR the lower and have a multi caliber SBR rifle. 

4. It's a low shelf lower, so it will accept a RDIAS and shoot 308/556 in FA.