View Full Version : short stroking AR
truckie453
03-01-10, 23:44
Hey guys,
My first AR related post here goes...
So I took my new LRB lower / Del-Ton upper AR out to the range today. She was short stroking every three or four rounds. The ammo and mags are not suspect as they function in my colt carbine with no issues.
No fte's only ftf's. I believe this to be a short stroking issue as she wouldn't lock open when one round was chambered and fired.
The rings look good, the gaps were staggered.
Someone suggested I was not running wet enough or that I needed to take fine steel wool to the bcg as it is brand new... any thoughts?
20" rifle length upper 1/9 twist, LRB lower (that I assembled), A2 Stock (cause I live in NY), using 55grn Remington UMC Ammo
Thanks!
Thomas M-4
03-01-10, 23:54
Hey guys,
My first AR related post here goes...
So I took my new LRB lower / Del-Ton upper AR out to the range today. She was short stroking every three or four rounds. The ammo and mags are not suspect as they function in my colt carbine with no issues.
No fte's only ftf's. I believe this to be a short stroking issue as she wouldn't lock open when one round was chambered and fired.
The rings look good, the gaps were staggered.
Someone suggested I was not running wet enough or that I needed to take fine steel wool to the bcg as it is brand new... any thoughts?
20" rifle length upper 1/9 twist, LRB lower (that I assembled), A2 Stock (cause I live in NY), using 55grn Remington UMC Ammo
Thanks!
I would try some different ammo Remington umc is very weak ammo.
I had some remington UMC last spring that gave me a couple of short strokes.
Like Thomas said, UMC is weak. But I still think it should cycle it. You might just need your gas ports opened up a little to do so. Or you could try taking weight out of the buffer.
truckie453
03-02-10, 00:15
I would try some different ammo Remington umc is very weak ammo.
I had some remington UMC last spring that gave me a couple of short strokes.
Thanks, I will definitely try some different ammo, I had not thought of it as the weak point.
truckie453
03-02-10, 00:16
Like Thomas said, UMC is weak. But I still think it should cycle it. You might just need your gas ports opened up a little to do so. Or you could try taking weight out of the buffer.
Is there a specific weight that the buffer should be? Is this something I can do myself (this is my second AR and and my first "built by me" AR)
spamsammich
03-02-10, 01:02
Leave the buffer for now, try different ammo, then decide if you need to mess with the buffer. Also, check your gas key to make sure it isn't loose. I'm betting it is loose, my cousin's Del Ton BCG was neither staked, nor tightened to spec. He shot it loose in a jiffy. I was not impressed.
Jay Cunningham
03-02-10, 03:59
Make sure that you are in fact using a rifle buffer. Perform the gas ring test (gas rings don't need to be staggered, BTW) and check that the carrier key screws are tight and staked.
+1
I'd check ammo, gas rings, gas key, gas port size in this order
Failure2Stop
03-02-10, 06:23
Make sure that you are in fact using a rifle buffer. Perform the gas ring test (gas rings don't need to be staggered, BTW) and check that the carrier key screws are tight and staked.
This.
truckie453
03-02-10, 08:16
Make sure that you are in fact using a rifle buffer. Perform the gas ring test (gas rings don't need to be staggered, BTW) and check that the carrier key screws are tight and staked.
the buffer is longer than my carbine buffer the spring is longer too. Is there a specific weight or length I should be looking for?
truckie453
03-02-10, 08:16
Thanks you guys are great. I will check and hopefully get her running right.
truckie453
03-02-10, 08:18
Leave the buffer for now, try different ammo, then decide if you need to mess with the buffer. Also, check your gas key to make sure it isn't loose. I'm betting it is loose, my cousin's Del Ton BCG was neither staked, nor tightened to spec. He shot it loose in a jiffy. I was not impressed.
I will definitely try new ammo and check staking before I mess with the buffer.
Belmont31R
03-02-10, 08:26
Check the spring length if you can or even try a different USGI one from Colt. If your spring is too long or too stiff it can cause short stroking.
One of the perils of buying commercial parts is they are all not made to one standard.
When you rack the BCG do you feel any specific spots where it feels like its rubbing on something?
Check around the FSB for gas leaks. A little bit of residue is normal but if it looks like there is powder burns you are probably leaking too much. Also why you are there check to make sure you have a gas tube pin in the FSB. It will be on the horizontal part of the A.
Check the carrier key for tightness.
They are right....gas rings on the bolt do not need to be staggered. Its a bit of a myth. Also make sure you have 3 of them, and that the bolt is somewhat tight in the bolt carrier. If it feels really loose its probably time to replace them. Even new rings can be bad...
And yes shoot it with some good 5.56 pressure ammo (M193 or M855). Worst case the rifle length system is just a bit undergassed to where that 'crap' UMC wont cycle it reliably and you need to use some hotter stuff. It technically should cycle that ammo but its on the bottom end of ammo regarding use in an AR due to being so weak. It does have a 5.56 chamber, no?
the buffer is longer than my carbine buffer the spring is longer too. Is there a specific weight or length I should be looking for?
seems like you already have the correct spring and buffer.
the only thing you can check about this items is the free lenght of the spring: it should be between 11 3/4 and 13 1/2 inches
truckie453
03-02-10, 10:56
seems like you already have the correct spring and buffer.
the only thing you can check about this items is the free lenght of the spring: it should be between 11 3/4 and 13 1/2 inches
Thanks for the confirmation, I checked the spring and it was 12-1/2"
truckie453
03-02-10, 10:58
Check the spring length if you can or even try a different USGI one from Colt. If your spring is too long or too stiff it can cause short stroking.
unfortunately my colt is a carbine so the buffer and spring are different.
One of the perils of buying commercial parts is they are all not made to one standard.
When you rack the BCG do you feel any specific spots where it feels like its rubbing on something?
I had not noticed but I will check more carefully when I get home
Check around the FSB for gas leaks. A little bit of residue is normal but if it looks like there is powder burns you are probably leaking too much. Also why you are there check to make sure you have a gas tube pin in the FSB. It will be on the horizontal part of the A.
Check the carrier key for tightness.
They are right....gas rings on the bolt do not need to be staggered. Its a bit of a myth. Also make sure you have 3 of them, and that the bolt is somewhat tight in the bolt carrier. If it feels really loose its probably time to replace them. Even new rings can be bad...
And yes shoot it with some good 5.56 pressure ammo (M193 or M855). Worst case the rifle length system is just a bit undergassed to where that 'crap' UMC wont cycle it reliably and you need to use some hotter stuff. It technically should cycle that ammo but its on the bottom end of ammo regarding use in an AR due to being so weak. It does have a 5.56 chamber, no?
Thanks for the info, I guess the easiest to do first would be better ammo. If only my job didn't get in the way of range time... :D
The ammo may be weak, but it should work with that ammo. I have run it through my HK416 which has an even heavier spring and buffer without a problem.
Definitely try stronger ammo, though.
If your buffer is longer than the carbine buffer, it's a rifle buffer. There will be a roll pin in it, you can push this out and remove weights. It's just something you can do to tune your gas system. But you should check the things the other guys mentioned, as you want to make sure everything is working properly before tuning it.
Definitely check the fsb. I had the same prob with one of my ar's. Fired it from the hip one day at the range and saw a small amount of gas leaking from my gas block. That cured my 'clicking' problem after torquing I correctly. Like the others said check your bolt carrier as well. Is it just barely staked as I call it?
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