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View Full Version : ar shortstroking! help!


rspeed9i6
09-24-2010, 7:00 PM
clean and lubed weapon
dpms 16" barrel carbine length gas system
rra bcg
american eagle xm193 5.56


when shooting, case is left inside the bore, does not cycle a new round. have to manually rack and case extracts, loads a new round. had gun shop replace normal gas rings for single piece gas ring and put an o-ring spacer on the extractor spring, went and shot it today and it still has the same problem. had a friend fire it as i watched the bolt and compared it to another guys ar. the other guys' seemed to cycle farther back then mine.

never had this problem when the weapon was brand new. it fired flawlessly up until about 400 rds were fired through it. so i dont think it could be a buffer spring. springs usually get weaker the more its used.

gas system problem? leak? bad ammo batch? i used some brake clean today to squirt inside the gas tube and it seemed like some slight fluid was seeping out of and around the gas block....should the gas block and tube be tight enough to prevent liquid seepage?...if so, this may be the problem.

what do you guys think?

Flagstar
09-24-2010, 7:16 PM
I had the same problem with my midlength AR as well, so I changed the buffer spring (make sure it's carbine) and replaced the buffer to Spike's buffer... had no problem eversince.

IsaacGlass
09-24-2010, 8:06 PM
clean and lubed weapon
dpms 16" barrel carbine length gas system
rra bcg
american eagle xm193 5.56


when shooting, case is left inside the bore, does not cycle a new round. have to manually rack and case extracts, loads a new round. had gun shop replace normal gas rings for single piece gas ring and put an o-ring spacer on the extractor spring, went and shot it today and it still has the same problem. had a friend fire it as i watched the bolt and compared it to another guys ar. the other guys' seemed to cycle farther back then mine.

never had this problem when the weapon was brand new. it fired flawlessly up until about 400 rds were fired through it. so i dont think it could be a buffer spring. springs usually get weaker the more its used.

gas system problem? leak? bad ammo batch? i used some brake clean today to squirt inside the gas tube and it seemed like some slight fluid was seeping out of and around the gas block....should the gas block and tube be tight enough to prevent liquid seepage?...if so, this may be the problem.

what do you guys think?

Check and see if the gas key loose??

beetle
09-24-2010, 8:13 PM
I had a new AR that developed short stroking problems after about 200 rounds. I checked all of the normal things, gas key, etc.

Ultimately it turned out to be a defective buffer tube. Check the inside of your buffer tube, the wear marks (if any) should be even. If it appears that one side has scratches it could be a similar problem.

rspeed9i6
09-24-2010, 8:45 PM
gas key is tight....will have to check the buffer tube+spring

rspeed9i6
09-24-2010, 10:17 PM
checked and inspected buffer tube and spring...buffer tube seems to have even wear on the inside. nothing that stands out. ive also looked over past receipts of what i was sold. looks like i was sold a carbine buffer and carbine buffer spring. (unknown weight of the buffer)

ive been snooping around calguns and found a thread talking about different weights of buffers. from what ive read, certain weights of buffers can cause short stroking.

now correct me if im wrong, but what im getting is heavier buffers will reduce felt recoil and will have more inertia to help force the bcg forward. but at the same time takes more force to shove the buffer backwards, and if good ammo is not used, it may not be able to force the buffer all the way back, causing a short stroke.

if this is true, would i want a standard, lighter carbine buffer to help alleviate the short stroke problem? or switch up the ammo being used? or both?

ive used pmc bronze .223 and was using AE xm193 5.56 when the problem occured. (please note, ive used the AE xm193 with no problems when the gun was brand new.)

im in a pickle...thx for the help guys!

G-forceJunkie
09-24-2010, 10:59 PM
I would first try a couple different brands of ammo, perhaps you just got a bad batch. Next I would start investigating the gas system. Perhaps the gas block, or the hole in the barrel are blocked with a bit of a shaved jacket. Gas block is not a liquid tight seal on the barrel, that sounds normal.

rspeed9i6
09-24-2010, 11:10 PM
I would first try a couple different brands of ammo, perhaps you just got a bad batch. Next I would start investigating the gas system. Perhaps the gas block, or the hole in the barrel are blocked with a bit of a shaved jacket. Gas block is not a liquid tight seal on the barrel, that sounds normal.

ok thanks...good info...maybe ill try some of the pmc bronze again....i have some hornady tap, but that stuff im saving for shtf....:)

rspeed9i6
09-28-2010, 10:02 AM
checked and inspected buffer tube and spring...buffer tube seems to have even wear on the inside. nothing that stands out. ive also looked over past receipts of what i was sold. looks like i was sold a carbine buffer and carbine buffer spring. (unknown weight of the buffer)

ive been snooping around calguns and found a thread talking about different weights of buffers. from what ive read, certain weights of buffers can cause short stroking.

now correct me if im wrong, but what im getting is heavier buffers will reduce felt recoil and will have more inertia to help force the bcg forward. but at the same time takes more force to shove the buffer backwards, and if good ammo is not used, it may not be able to force the buffer all the way back, causing a short stroke.

if this is true, would i want a standard, lighter carbine buffer to help alleviate the short stroke problem? or switch up the ammo being used? or both?

ive used pmc bronze .223 and was using AE xm193 5.56 when the problem occured. (please note, ive used the AE xm193 with no problems when the gun was brand new.)

im in a pickle...thx for the help guys!

could anyone shed some light on the buffer being a probability?

evolixsurf
09-28-2010, 10:43 AM
what does your buffer say on it if anything? You probably have the standard carbine buffer which is the lightest. See if it has H or H2 on it. That would mean its a heavy or heavier one. I would get compressed air and shoot it into your gas tube to make sure nothing is stuck in there. Hopefully whatever(if anything) is stuck in there it will come out. Also check to make sure your gas block is aligned over the gas port in the barrel.

evolixsurf
09-28-2010, 10:43 AM
and you are right on your thoughts of the buffer system

evolixsurf
09-28-2010, 10:46 AM
do you have a friend with another bolt you can borrow? I would try throwing that in there and see what happens.

rspeed9i6
10-05-2010, 8:12 PM
hey guys...took it to sac black rifle where i purchased the upper from.....found the problem in the gas block...one of the screws was loose enough to allow the gas block to slowly creep forward on the barrell everytime it was fired....they reset the block and used locktite on the screws....problem solved...

thx for all the help guys

G-forceJunkie
10-05-2010, 10:40 PM
And that is why I like a plain old original style forged site that is pinned on. Glad you got it fixed.