My friend just bought a 2009 polytech M14 and was having trouble with it short stroking everytime he shoots it. So brought it to me to have a look at it, and i went through all the usual culprits. Dirty gas cylinger, gas cylinder mis allined with vent hole in barrel, gas valve closed, poorly fitting gas piston. Everything checks out perfect. Then I tried the tilt test, and after applying a little grease where it was needed it passes out of the stock, and in the stock with the trigger guard removed. I also confirmed that the op rod is not making contact with the stock along its hole line of travel. Still after confirming all of this it still will fire a round, eject it, chalk the hammer but wont strip a new round into the chamber. The only two things left that i can see are that his two 5 round (not 5/20 round mags) mags seat very hard and you feel alot of resistance when operating the bolt, witch might be slowing the bolt traval causeing it the short stroke. Or that the ammo he's using witch i didn't recommend to him is causeing it. Ammo is Remington 150g core lock. Any ideas from the experts, really I'm still a novice in the M14 game.
M14 Short Stroking
- Thread starter lorne19
- Start date
Remington core loc is ok ammo. I had a bad batch of winchester ammo once that was weak, so it can happen.
The basic operation relies on some of the gas from the firing of the round to exert pressure on the piston, which in turn forces the bolt all the way to the back, the op rod spring then forces the bolt closed. There is only a finite amount of energy in the gas released and it is very likely that it is lost in some form of excessive friction loss. I say this because the bolt is not going back far enough to pick up the next shell.
Check a couple of things:
1) Is the op rod binding/touching anywhere on the rifle stock or is there any kind of binding with the spring and the op rod guide? A tilt test shows that the bolt and op rod move freely without tension, but what about when the spring is loaded? One of the first things I did as I bought my rifle was bought a better op rod guide (with a nicely machined one) at the recommendation of the store.
2) Is the op rod binding anywhere along the receiver? Lubricate the thing.
3) Inspect the trigger assembly, make sure the hammer is lubricated and not binding in it's operation. Loosen it up by working it a bit.
**Buy some 308 snap-caps. Never use live ammo!**
4) Load in two, three, four and five snap caps into the magazine. Cycle the rifle. You should feel some serious tension to pull back the hammer, but after that it should be relatively free. Once the snap cap is chambered, DO NOT PULL THE TRIGGER, rather, remove the magazine and work the bolt a few times. Again, without pulling the trigger, put a full magazine in again, and cycle the bolt. It should not bind or take excessive energy to move it.
5) If there is binding on the bolt, check to see whether it is somewhere on the receiver (bolt path), magazine or the trigger mechanism.
6) Buy a spare magazine and see if there is the same tension on it.
7) Try another brand of ammo.
The basic operation relies on some of the gas from the firing of the round to exert pressure on the piston, which in turn forces the bolt all the way to the back, the op rod spring then forces the bolt closed. There is only a finite amount of energy in the gas released and it is very likely that it is lost in some form of excessive friction loss. I say this because the bolt is not going back far enough to pick up the next shell.
Check a couple of things:
1) Is the op rod binding/touching anywhere on the rifle stock or is there any kind of binding with the spring and the op rod guide? A tilt test shows that the bolt and op rod move freely without tension, but what about when the spring is loaded? One of the first things I did as I bought my rifle was bought a better op rod guide (with a nicely machined one) at the recommendation of the store.
2) Is the op rod binding anywhere along the receiver? Lubricate the thing.
3) Inspect the trigger assembly, make sure the hammer is lubricated and not binding in it's operation. Loosen it up by working it a bit.
**Buy some 308 snap-caps. Never use live ammo!**
4) Load in two, three, four and five snap caps into the magazine. Cycle the rifle. You should feel some serious tension to pull back the hammer, but after that it should be relatively free. Once the snap cap is chambered, DO NOT PULL THE TRIGGER, rather, remove the magazine and work the bolt a few times. Again, without pulling the trigger, put a full magazine in again, and cycle the bolt. It should not bind or take excessive energy to move it.
5) If there is binding on the bolt, check to see whether it is somewhere on the receiver (bolt path), magazine or the trigger mechanism.
6) Buy a spare magazine and see if there is the same tension on it.
7) Try another brand of ammo.
If it's not a piston or gas plug full of carbon
If it's not poor gas port alignment
If it's not binding on the stock or receiver
Pull out the oprod and spring so it's not in the way.
Point barrel up and push in the piston. It should drop relatively slowly. If it drops fast.... You might need a new piston.
If yer mag is too tight, take a few thousands of an inch of the botton edge of the mag's locking tab. Use a caliper and work slow with a file untill it locks in snug but has less upward pressure on the bolt. Do not get too carried away, the adjustments should be minimal.
If it's not poor gas port alignment
If it's not binding on the stock or receiver
Pull out the oprod and spring so it's not in the way.
Point barrel up and push in the piston. It should drop relatively slowly. If it drops fast.... You might need a new piston.
If yer mag is too tight, take a few thousands of an inch of the botton edge of the mag's locking tab. Use a caliper and work slow with a file untill it locks in snug but has less upward pressure on the bolt. Do not get too carried away, the adjustments should be minimal.
Everything else checks out, gas piston is fine. I took your advice and took a few thousands off of the mag. It made a big difference when putting the mag in and out, much easer. When I get home tonight from work I'll try to run a fe rounds through her and post an update.
Well I got home tonight and tryed her out. My first attempt was a failure, still short stroking. but the mag fit still bothered me, so i figured i had nothing to lose by takeing a few thou more off. After that bingo 5 rounds down the pipe just has fast as i could pull the trigger. It would appear that this rifle came with two crappy 5 round mags. Thanks for the tip Doc.
