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My other post is not getting much traction as far as the particulars of the gas system so I thought I would post a specific question.

I would like a detailed functional and mechanical explanation of just exactly how the gas system can effect help/hinder accuracy.

Thanks
 

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1) Any 'gas system' (and any semi-auto) cannot help accuracy - a bolt-action is mechanically more accurate as long as it is designed and built well.

2) 'Gas systems' all have parts that move and vibrate while the bullet is still in the barrel.

Consistency is the major factor that gives accuracy - the fewer 'moving parts' the better.

Jay Kosta
Endwell NY USA
 

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It has already been stated a bunch of ways, but consider this:

Find a good benchrest (competition) type rifleman. These are the guys that shoot "Bug Holes". They are the guys that can literally kill a fly from 100 yards away with EVERY shot. Hitting a thumbtack from 100 yards is easy. It is still pretty reliable for them to do this out to 200 yards.

Tell him that you would like to change the rules a bit on him:
1. He can no longer neck size only. He must full length size all his ammunition.
2. He has to use .308 or 7.62 NATO cases. He can't select from a batch of 6 mm PPC.
3. He can't index cases. He must cycle them through his gun violently and eject them with force out into the dirt.

Next, tell him that you want to modify his rifle a bit:
1. Clamp a flash hider on the end of his barrel.
2. You are gonna drill a hole on the bottom of his barrel.
3. A bunch of movable weights are going to be clamped onto his barrel. They will move around with each shot and hopefully return to where they started.
4. at the same point as the hole in his barrel, there will be a pressure point to the stock. It can't be free floated any more.

He will probably tell you to forget about accuracy from that contraption. I had this conversation with a couple benchrest guys at our range. They were amazed that I was able to consistently shoot well under MOA with that monster battle rifle.

Then again, not all semi autos work the same. The German G3 / HK 91 DOES have a free floated barrel, no gas system and nothing much moves when firing except for the roller locked breech. Then again, I have only shot a few HK 91 types but would bet my M1A will out shoot them every time. (Well, just about every time. I don't want to tempt any Gremlins!)

- Ivan.
 

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Gas Gun Accuracy

Contrary to some of the previous comments, the M14 can be made into a very accurate rifle. Even so, it will not be a bench rest rifle.. The best M14s are capable of 1/2 minute accuracy and sometimes better, but they are rare. Most will shoot 5/8" to 1" groups with all the accuracy modifications. These rifles are designed and intended to be shot across the NRA HPR course from 200 to 1000 yards. The accuracy requirement for this type of shooting is 2 minutes of angle or better. They are not designed to shoot one hole groups.
 

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I'm telling you right now, it's some black magic voodoo stuff. Swapping pistons, tightening things up, aligning everything, sacrificing a chicken... it's crazy. The basics are tightening and aligning. But if your rifle doesn't like a piston for whatever reason it can hose the groups.

Something to check, see if the piston tail has any contact marks from the cylinder D hole. Surface contact between the two is bad. I once got a new piston with a slightly bent tail, just enough so the first two thirds of travel contacted the D hole (piston moving back to eject a round), accuracy suffered. I swapped out for another piston I had and accuracy was back where it should be.

Why any of this makes a real difference is beyond me, I just know it does. Even gunsmiths can't fully explain why a rifle may like one piston over another. Like I said, black magic voodoo stuff.
 

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Swapping pistons can make a HUGE difference in accuracy - My rear lug shoots 1in & under with a old GI piston - It shoots just under 2in with a Sadlak!! - I have a box full of pistons & i swap em' around until i find one that each individual gun likes
 

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(Most) semi-automatics are bolt actions until the bullet passes the gas vent, then more when it leaves the barrel. The gas system is doing nothing until then. It is not interracting with the bullet. The vibration of a closed titanium piston held in place by a tight oprod spring should be pretty non-existent and vastly less than your fleshy body holding the gun.

There are plenty of semi-automatic sniper systems. That action itself has a stigma against it from many many years of misinformation and, in my VERY humble opinion, a bit of shooter snobbery. Of course, it didn't help that a lot of the earlier semis had problems like jamming and fouling and such. And the M14 gets pretty damn dirty. A bolt action is obviously a very simple design and that's easy to respect.

The action of a gun defines how the gun is loaded and rounds are cycled. The primary affects of accuracy on any gun are bullet and barrel, which make up the tremendous lion's share of accuracy (of a completely stationary gun).

I may be wrong, but I believe if you did the concrete block challenge of having a fixed M14 held in place by receiver and barrel and the same for a Remington 700, they would shoot nearly identical over 1000+ rounds. My .0002 cents.
 

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Swapping pistons can make a HUGE difference in accuracy - My rear lug shoots 1in & under with a old GI piston - It shoots just under 2in with a Sadlak!! - I have a box full of pistons & i swap em' around until i find one that each individual gun likes
My Scout didn't like a new Sadlak either. Put my original Springer piston back in and quit wasting money on that stuff. The shims to tighten the front band on the gas cylinder did do a major improvement on my rifle. That tip worked. Increased the dwell a bit too I hear.
 

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Hi Ted Brown,

Can you tell me which of the descriptions of the differences between a service rifle and a benchrest rifle you disagree with? I thought it was a pretty fair comparison. Yes, I KNOW they can be accurate despite all the limitations.

- Ivan.
 

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I'm glad I clicked on this thread guys. *high five!?* eh... ok

Thanks for posting this info, my scout was my first rifle but my collection has grown quite a bit and I haven't left a lot of attention for my scout lately. It's gonna be cool to do something as 'swap pistons' to see if it makes my rifle more accurate when I get it all finished.

Good question OP!
 
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