Short Stroke Problem

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12 years 2 months ago #12502 by ernierod
Short Stroke Problem was created by ernierod
Noobie in S/A rifles.Purchased a Armalite AR-10T in 260 Rem caliber about one month ago.Installed a Magpul PRS on rifle-seemed simple enough-slip off old stock,follow directions,slip on new PRS stock.Quality of rifle is great.Broke in new bbl per directions-single shot at a time.Problem:Bolt doesn't lock back on last shot.Doesn't pick up 2nd round either.Checked for binding/marks on operating spring,bolt assy,charging handle and magazines(2).Had an experienced AR builder help me dis-assemble/clean/lube-bolt assy,check gas block,check/clean gas hole in bbl,check for leaks,carefully aligned block,cleaned bbl,chamber and receiver.With a magazine installed-pulling charge handle back-it will lock back.Talked to Tim-of Armalite-was very helpful.Dis-assembled magazines(cleaned),slightly lubed with spray Molykote(MDS) and polished all binding surfaces of magazine follower with crocus/polish paper.Am wanting to use 139 to 142 gr quality bullets-for Load developement.Tried Car-Bon factory bullets(140gr) for reference-short stroking still persisted. No pressure signs showing.Total amt of shots,so far,53. Per Tims advice-use plenty of oil on bolt (perhaps not broken in yet??)Will try 3 HQ oils and try again.As a last resort-will return rifle to factory. Question-did I miss anything??? Any further advice appreciated. Cheers Erod

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12 years 2 months ago #12503 by Krisar10
Replied by Krisar10 on topic Re: Short Stroke Problem
I have the same exact problem, was told to do the exact same thing. But when i do cover the bolt carrier with oil it does perform the way it should. So i figure its still breaking in. The advise from Armalite was the same as well. Its also weird though because i run a suppressor with mine and it seems to work just fine when the can is on. bolt locks back and everything. I collect that it is just the brake in process. Let me know how things turn out.

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12 years 2 months ago #12529 by ernierod
Replied by ernierod on topic Re: Short Stroke Problem
Tested 140 gr bullets again. Per Armalite suggestion-soaked Bolt carrier assy with oil to no avail-would not even lock back using one shell for test.Tried FP-10,Mobile 1,Hoppes gun oil and CLP Break Free-none worked.However did notice on bottom-rear(near latch) of charging handle binding marks indicating a rubbing condition of approx. 4". I will sand down with emory,polish and blue area to see if condition persists-I don't really think this is the problem-but will try.Cheers

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12 years 2 months ago - 12 years 2 months ago #12557 by ernierod
Replied by ernierod on topic Re: Short Stroke Problem
Tried Remington Factory loads-no luck. Reluctantly will send to factory under warrantee. Rifle is not really broken in-bit I think it should work with factory ammo. As of today-10/16/2012 -75 shots-so far.Problem persists. Like everything about rifle-accuracy is great-too bad it is a single shot :-)
Last edit: 12 years 2 months ago by ernierod.

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12 years 2 months ago #12558 by jtallen83
Replied by jtallen83 on topic Re: Short Stroke Problem
Sounds like you gave it a shot to straighten out. They should be able to solve whatever your issue is. It is real unusual to hear about a true AR-10 malfunctioning. My basic model has never missed a beat from day one, no matter what I feed it or oil it with. I'm sure they'll get you in the same boat. Let us know what you find out.

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12 years 2 months ago #12562 by LebbenB
Replied by LebbenB on topic Re: Short Stroke Problem
It sounds like you have a gas leak somewhere in your rifle. The most obvious places to check: Gas block (it could be loose)or carrier gas key (loose or improperly staked.)

Its also weird though because i run a suppressor with mine and it seems to work just fine when the can is on.

This comment is telling. Because of the added back-pressure from the can, your rifle operates correctly. Are there any stress signs on the spent brass when you use the suppressor? If not, I'd wager that your barrel's gas port is a bit out of spec. If you know a good AR smith take it to him/her and him look at that.

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12 years 2 months ago #12572 by Krisar10
Replied by Krisar10 on topic Re: Short Stroke Problem
I am also still having issues with my Armalite not locking back or feeding the next round. funny enough i ran my suppressor today and it had no problems at all, i take it off and all the problems come back. Im thinking that the gas tubes not being lined properly could be our problem. i contacted my local gun smith with this issue, he said that it is most likely the gas tube. So hoping that it is, i will be bringing it to him. Would be nice if thats all thats wrong with it. Would really hate to have to sell it or trade it in. Although Colt did just come out with a Badass new 308 AR.

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12 years 2 months ago - 12 years 1 month ago #12585 by ernierod
Replied by ernierod on topic Re: Short Stroke Problem
Per Armalite suggestion I measured buffer spring-was 13.5" long. Did research on these type of springs-seems to be the normal range of springs should be 11.75" to 13.50" long.Suspect Armalite just might install a slightly shorter (weaker) spring and function check rifle-unless they actually find some other problem with rifle-like not enough gas pressure being routed to the BCA-to work the action.Cheers. Received from J.P. Enterprises a .308 buffer spring-although I didn't mike the coil thickness-the length of the spring was 12.5" Curious.**********
Last edit: 12 years 1 month ago by ernierod.

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12 years 1 month ago #12791 by Krisar10
Replied by Krisar10 on topic Short Stroke Problem
Just took my Armalite in to the the shop and showed my local gunsmith, he took one look at the gas tube alignment and said " yeah thats about a quarter inch off ". :thumbs: He repositioned it, set the screws with lock tight, and gave me the go ahead. :twothumbs: So for your short stroke problem..... check the gas tube alignment. I will be test firing it soon to confirm, but that sounds to me to be what was cause the rifle to short stroke. especially when i put my can on and it works perfectly, due to the added back pressure it is receiving.

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12 years 1 month ago #12852 by Krisar10
Replied by Krisar10 on topic Short Stroke Problem
Its confirmed my Armalite now shoots the way it should, without a mess of motor oil. So if your short stroke problem still exists check and center your gas tube and gas block. worked for me!!! Good luck!!

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