ar15 is short stroking?

[cjmac]

So my ar is short stroking i think. .its not picking up the next round out of mag .iv tried other mags ,checked gas system, measured and counted coils on buffer spring , lubed good . WTF is wrong with this gun ! Could the spring be to strong ?

 

[spclark]

What kind of (hand) load / factory ammo you tried?

Usual suspects are powder too fast / too much, not enough of the right powder... list goes on but until you can provide more info it's nor worth wasting characters....

 

[cjmac]

As of now iv tried federal (brown box) 55 gr fmj. PMC 55 gr fmj. Handloads im using TAC and ramshot X-terminator. With 55 , 52 and 69 gr sierra and hornady. Id have to look at the chare im using, cant remember.

 

[cjmac]

I know the charge is middle of the charge table maby a little higher

 

[cjmac]

If i remember correctly LC 62 gr ammo DID work. Maby it likes hot loads .

 

[LRPV]

Put one round in the mag to see if the bolt catch will indeed catch the bolt. I had a Shilen barrel that had a burr in the gas port that would not come out by firing it. I've always been told to check the gas anytime short stroking is mentioned. Also making sure gas block is not covering part of the port. Gas port size also. But, you said you already checked the gas system. I had one combination of upper/lower once that just didn't work. There was some misalignment somewhere and the BCG would drag when cycling the action. I never did figure out why since the upper worked on every other lower I had and vice versa but those two pieces just didn't work together.

 

[bsumoba]

lots of questions here to ask...

1) did you build this yourself?
1a) if yes, did you make sure the gas block is aligned properly?
2a) if no, what mfg is the upper? still could be misaligned gas block...

2) wrong buffer spring/weight combo? i know there is a "lighter" recoil spring out there that larue supplied me because their stock spring is designed for hot 5.56 ammo such as XM193 or green tip stuff
3) could be the mag springs are not strong enough? weak mag springs will cause what looks like short stroking during operation since it doesnt pick up a round. Did you try one round in the mag, shooting it, then seeing if the bolt locks back? I would do this first actually...this will tell you a lot if you're truly short stroking or have a bad spring/weight combo.
4) last but not least...check your gas rings on the bolt. if they looked damage, you got a problem and this could cause short stroking. one way (doesnt always work though...) is to take the bcg, extend the bolt to its extended position, then stand it on end bolt side down. if it stays up, you're probably okay with the gas rings. the best way is to visually check the gas rings though.

hope this helps.

 

[Huntsman]

I have experienced short stroking with X-terminator in my AR
I am using 26.8 grains and it will pick up the next round but wont hold the bolt open when the mag empties.
I have no problems when using BLC2 and H335.

 

[cjmac]

Its a colt upper . Iv tried the one round in the mag it wont lock open . Im starting to think buffer and spring . Like i said THINK the LC 62 grain green tip ammo did work . If a spring is not much ill try that before taking it to my smith

 

[fayettefatts]

I had a leaking bolt carrier key that drove me crazy for a while.

 

[cjmac]

Gas rings on bolt look good. That was first thing i checked

 

[cjmac]

I had a leaking bolt carrier key that drove me crazy for a while.

..how did you find out thats what is was ?

 

[fayettefatts]

I had a leaking bolt carrier key that drove me crazy for a while.

..how did you find out thats what is was ?

Rifle would only short stroke occasionally but got worse the more I used it. Like over the course of an entire shooting season! I finally realized that the carrier was dirtier than it should have been. Gas was leaking between the key and bolt body even though the carrier key bolts were tight. Look closely at the gap between the key and bolt body to see if there is any evidence of gas escaping there. May need a magnifying glass if your eyes are anything like mine! ;D

 

[spclark]

Cjmac, clean your upper thoroughly. Before you reassemble, carefully inspect both the gas tube and carrier key for wear where these parts engage. Then fit just the carrier to your upper & slowly move it back and forth to see if you can feel any intererence when the tube enters the key. Often just a little bit of a bend can cause the tube to misalign & the friction ends up slowing the bolt cycle enough to cause a problem. If the tube is bent up a bit you won't see it during a visual inspection.

 

[Stumpy1]

Another thing to take a look at would be to make sure the carrier can go all the way back, and that the bolt catch is catching the BOLT and not the carrier.

If it won't go back, make sure that the screw holding on the buttstock isn't too long -if you have changed the stock and are using a long screw (like from an A2 stock) where you don't need to, the buffer can bottom out on the screw (you can check the bottom of the buffer for impact damage)

I have seen this a couple of times, so it can't hurt to check

IF, on the other hand, it used to work, no mods have been made, and now it doesn't, the folks who responded before me have given you plenty to look at.

Frank

 

[cjmac]

Yeah just looked at that this morning. Really staring to think the buffer is to heavy. Military LC 62gr ammo worked i think .but its pretty hot stuff.

 

[ridgeway]

What buffer do you have in it now?

 

[carlsbad]

AR 15 uses a heavy buffer and heavy spring. Most short stroking eventually turns out to be a gas flowpath problem. In most cases either the gas block isn't aligned with the gas port on the barrel correctly, or the gas block is loose allowing significant leakage of gas. That's been my experience. --jerry

 

[cjmac]

I honestly cant remember who the buffer was from . Is the gas block is leaking i can't tell ,theres no soot .im guessing theres no other way to tell if it is

 

[mac86951]

AR 15 uses a heavy buffer and heavy spring. Most short stroking eventually turns out to be a gas flowpath problem. In most cases either the gas block isn't aligned with the gas port on the barrel correctly, or the gas block is loose allowing significant leakage of gas. That's been my experience. --jerry

+2 to that one.

In my experience, I am using heavy buffers, M16 Carriers, Tubb Bolt weights, and an adjustable gas block turned down to slow down the timing for long range. If Factory Ammo is being used (and it sounds like it is), I would expect a gas port alignment issue/gas delivery issue first.

Is the rifle hard to cycle using the charging handle? A misalignment of some part (others have mentioned gas tube) would be my next guess.

Buffer spring could be the issue, but really only if there is a length problem (which you'd know by cycling by hand), or if you chose AR10 parts for your AR15 (they'll fit, but the springs are a bit stiffer).

-Mac