AR Short Stroke.

B

BlackJackID

New member
A few months ago I bought kind of a mutt of an AR-15, which has been completely reliable, as long as I feed her brass, which I intend to do as long as times allow. However, Tula/wolf et al. short strokes every time.

The Rifle is a colt M16-A1 parts kit put into a CMMG lower receiver. Its really a great gun and definately worth the 550 I paid for her. is the short stroking being caused by the buffer/spring combo? or is it perhaps due to the Mil Spec (full auto) bolt carrier? I have heard of people putting carbine buffers in , but I'm not convinced this would cure the problem.

As I said, I dont intend on shooting the cheap stuff, but I want the parts , just in case. Any help would be appreciated
 
If it's a former GI gun sold as a parts kit the chamber may have excessive wear. The brass casings are going to expand more than the steel and thus form a tighter seal. You may have an issue where there isn't enough gas pressure making it to the gas tube to cycle the BCG.
 
Sails,

Thanks for the reply, but I dont think thats the issue. The Parts kits were new, but even if they hadnt been, a new barrel was put on (sorry I didn't indicate that in the previous post).
 
My guess is that the steel cased ammo isn't generating enough gas pressure for your port size/buffer/spring combo. If you want to optimize towards the steel case (at the expense of reliability with brass case ammo), you could try a lighter weight carrier or a lighter buffer. Ultimately, you could drill the gas port out a little bit; but I'd think about that first since that one is irreversible.
 
It could be the bolt carrier, though I would think that the heavier M16 carrier would work better, not worse. I had a half moon cut, ban era Colt bolt carrier that wouldn't feed anything with a steel case. It ate every brass cased load I fed it, including reloads all over the spectrum.
I popped an Armalite standard AR carrier in it once, and it ran like a champ with Wolf. Back to the Colt half-moon carrier; more short stroking.

To check this possibility, just swap out the bolt and carrier.

Other things:
-Is the gas key hanging up/dragging on a slightly misaligned gas tube? You should be able to feel that by slowly hand cycling the bolt carrier.
-Magazine issue-feed lips dragging on the carrier excessively?
-possible issue with the combination of a M16 carrier and a notched AR15 hammer causing some sort of dragging issue upon cycling?

If those don't work, toss in a lighter buffer and spring.
 
I'm with Bartholomew Roberts.

The cheap Russian ammo seems to be a bit underpowered in .223, and the result is it isn't generating enough gas pressure to give a full movement of the bolt and carrier while cycling.

About the only change I'd be willing to make to my rifle if I had this issue would be to try a lighter buffer, but quite honestly, I'd be more likely to sell off the cheap ammo and chalk it up to experience. Wolf isn't so much cheaper than some other surplus ammo types that it's worth the trouble with the ARs.
 
^ What he said. Try out a carbine buffer. If that doesn't work, no big deal. Wolf is generally inexpensive and unreliable problem ammo anyway.
 
I forgot to mention it; but it is always worthwhile to run the standard troubleshooting for short stroking. Check the gas key, check the gas tube alignment, check the gas rings, check the action spring length. You may be right on that functional edge where you have a minor problem that only pops up with lower powered ammo.
 
I had a similar problem with WPA ammo and my newest 16" middy. I was short stroking when I had one of my two rifle lowers attached to the middy upper. Rifle buffers weight 5.5 oz vs the 3oz for standard weight carbine buffers. I swapped out the a rifle lower for a carbine lower the short stroking stopped.

Another option for me would have been to keep my rifle lower and put in a $50 LMOS JP rifle buffer:rolleyes: So rather than spending $50, I spent $12 on a standard rifle buffer, dissembled it and swapped the steel weights for delrin rod pieces of the same size to bring it to 3oz - its basically what JP does plus a fancy red paint job:D
 
Good Guide for troubleshooting says it better than I can. I have it bookmarked.

http://www.ar15armory.com/forums/AR15-Troubleshooting-Tec-t5332.html

To see if you have a short stroking problem and not a “Failure to Feed” problem, please perform this test first (assuming your bolt catch and magazine is functioning properly). Insert one round into a magazine that you know to be performing well. Insert the magazine into the magazine well, pull the charging handle to the rear, then release the charging to load the round into the chamber. Safely discharge that round. After the round has been fired the bolt should automatically be locked to the rear by the bolt catch and the empty magazine. If the bolt is closed on the empty chamber, then it did not travel far enough to the rear to be held by the bolt catch, and your rifle has short stroked.
Short stroking is a symptom of a problem with the gas system in the rifle. There are 7 parts of the AR gas system. In the upper receiver group, you have the barrel (gas port), front sight base, and gas tube. In the bolt carrier group you have the gas key, the carrier, the bolt, and the gas rings
Click to expand...
 
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