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Ar Problem(s)


revchuck

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I just picked up a standard configuration AR-15A2. It had been built with a Bushmaster lower, somebody's upper, and a FN GI barrel. I finally got a chance to take it to the range today, and I'm not a happy camper.

Almost immediately I started having failures to feed. I was using Remington green-and-white box 55 grain ammo from Wal-Mart. When the jams occured, they were nose-up with the bolt part-way up the case. It appears that the bolt didn't go back far enough to catch the rim. Also, the bolt didn't lock back after the last shot - apparently it didn't go back far enough to engage the bolt release. If I manually retracted the bolt all the way, it caught properly. Extraction was fine, if somewhat lazy. The magazines were a 20 round Colt and a 30 round generic GI.

I'm thinking it's an ammo-related problem, with the ammo being too lightly loaded. Shoot, it was like shooting my 10-22, except I had the buffer spring sound in my ear. I've been shooting my Uncle's M16s since 1974, and there was always more recoil than this with both 55 and 62 grain issue ammo.

If this is an issue with that ammo, I just know to stay away from it; what's a good ammo to try that's hot enough to run a stock gun?

If it's not the ammo, where do I check to find out what the problem is?

Thanks!

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im in the army and work in a weapons shop, we see this problem on the range alot you might check your firing pin retaining pin it could be in wrong, ie right to left instead of left to right. other then that i would have to see it do you have any pics when you manual work the bolt does it drag alot or is it smooth. also if you have not taked the buffer and sring out there could be a rag or something in there. sad to say this has on the range also got to love the desk soldiers.

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See if the gas block opening/system is lined up correctly...

Lots of good advice in this thread, but I would start with Merlin's suggestion and also look and make sure the carrier key is good and tight.

Is the carrier properly lubed? If it's new you might have to run pretty "wet" for the first few hundred rounds.

Good Luck,

Ed

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If it won't run with the Remington green/white box stuff something is wrong. That

ammo isn't quite as hot as some, but my guns run it fine.

Your gun is short stroking. Usually it's one of three things.

1. Not enough gas doing what it's supposed to do.

Mis-aligned/plugged gas block. Plugged/worn gas tube. Loose/plugged carrier key.

Totally crudded up piston. Ring gaps lined up. Or something else screwed up with the

gas system.

2. Too much recoil system.

Wrong recoil spring. Wrong buffer.

3. Friction.

Dry cruddy carrier. Mag catch too high, dragging mags on the bolt. Dirty chamber.

Friction is the easy one. Clean it, cycle it. If it isn't smooth then something is dragging.

Gas system problems will drive you slightly nuts. Especially if it's a gas block/gas port

alignment problem.

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If it will not lock back after the shot with a single round in the mag every single time, you are not getting enough oomph into the operating system.

The first thing I would do is go get some Federal premium grade ammo and do the one round in a mag and lock back test. If the gun locks back with single rounds in the mag and feeds rapid fire reliably with first quality fodder you have a good gun and you need to stop feeding it that cheap stuff. If it fails the test with premium ammo, take the gun to a smith who specializes in AR's if you want to keep it, or back to whoever built it/sold it if you think they know what they are doing.

If it is built right, the gas rings all having their gaps aligned is the only real mechanical possibility here other than something actually being broken.

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Thanks for all the replies!

What I've done so far: Cleaned it, including taking the bolt all the way down. The bolt was nasty inside, but not so much that it should have impeded function. (Before firing it, I had lubed the bolt carrier with commercial Break-Free; it always worked with M16s, so I guess it should've worked with this rifle. Also, the bolt slid back and forth within the carrier about the same as the 16s I've had in the past.) The bolt carrier key was clear, and the allen bolts holding it on are tight and well staked. I'm not sure how to check the fit of the gas tube to the front sight; it's in there tight, and there was no powder residue on the inside of the handguards or the handguard-holder-thingy (technical term ;) ) where the gas tube enters it.

Things I've noticed: The buffer spring does seem stiffer than I'm used to in an M16. Also, the bolt carrier is different in that the rear third of it is cut out so that it only goes about 2/3 of the way around, instead of being a complete circular piece. It was obviously made this way, rather than being broken, and I don't know whether it would influence the operation of the rifle.

Things I'm going to do: Order some Federal AE 55 grain FMJ and 50 grain JHP, and some Gold Medal 69 grain JHP match ammo. I'll use it to do the load-one-round test. I'm also going to order a buffer spring from Brownell's, since I have to order some .22 bore brushes and a chamber brush from them anyway.

If y'all can think of anything else, let me know!

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Check the gas rings. Pull the bolt and carrier out. With the bolt extended, stand it on the bolt. If the weight of the carrier closes the carrier in the bolt, you have worn rings.

Keys can be staked but still loose. Grab the key and try to move it. If there is any movement at all, you need to re-do the key assembly. Remove the screws and key, degrease, (I even clena the threads with a tap) then apply a small amount of Loctite, and re-tighten. 50 inch-pounds, if you have a torque wrnech. Then re-stake.

Frankenguns can be a real headache. Your buffer spring may be too heavy. It could have come from a High Power shooter, who used the lower while shooting the heaviest bullets at the highest velocities he could manage. The heavier spring kept the gun from beating itself up.

The last thing is the truly counter-intuitive one: check headspace. A rifle under minimum headspace mimics a short-stroking low gas gun. Compressing the round in the too-small chamber pre-loads the locking lugs. When it fires, the frictional load increases greatly. Such rifles can have so much energy sucked out of the system just unlocking the bolt, that they then short-stroke.

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Replace the carrier key and the gas tube. If you shoot a lot of 3 gun you probably should do this every year like changing mag and recoil springs on your pistol.

Brownells sells a replacement kit for $30.00

231-000-045 Rifle Gas System Kit

When you replace the gas tube make sure you have proper alignment of the tube, gas block, and gas port on the barrel. If you have a adjustable gas block after replacing the gas tube and carrier key open it up all the way and then adjusted it down until the rifle will not cycled based on the ammo you are using, then you will know where to adhest up from for reliability.

If the problem is intermittment I bet you a dollar it is the gas tube and carrier key fit.

The problem is not the buffer spring, it is a gas problem.

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I don't think it's a question of wear - the finish seems almost brand new on the receiver and the bolt and bolt carrier, and the step on the end of the gas tube is quite pronounced. It seems to be more of a situation where the gun was put together on a pre-ban receiver and didn't run 100%; it was stuck in a safe for about ten years, until after the sunset of the AWB. Nobody ever de-bugged it, so I'm the lucky one. ;)

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Highly doubt this is the case, but, having slogged through a prolonged exercise of this sort, checking/trying most if not all of the preceding...one more thing to check...

If you have a one-piece/McFarland gas ring - revert to the three-standard-ring setup.

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What type of stock?

What is the gas port size?

Standard A2 buttstock and fore end; I haven't the foggiest about the port size. I've never taken an AR apart past field stripping, and don't want to learn without on-hand guidance from someone who knows how, because that usually involves a trip to the gunsmith with a box of parts and a sheepish smile. :lol:

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Well, I got in the ammo and parts I ordered and made a quick trip to the range today. I replaced the buffer spring with a standard one from Brownell's. The ammo was Federal American Eagle 55 grain FMJ and 50 grain JHP, Federal Match with the Sierra 69 grain JHP, and some more of the Remington 55 grain FMJ. I liberally lubed the bolt carrier (shiny wet) before I started.

Results: The rifle functioned 100% with the American Eagle ammo, but locking the bolt back on an empty mag was a sometime thing. The Federal Match was 100%, including locking the bolt back. The Remington did the same as the last time - sometimes it would pick up the round okay, sometimes it would short stroke and jam, and sometimes it would eject the fired case and close on an empty chamber.

Any recommendations on whom to send it to? Is an AR gas system something the local works-on-anything gunsmith should be able to diagnose and fix? It could use a trigger job anyway.

I plan on keeping it. I was using an empty water bottle for a target during this session, shooting offhand, and was shooting and getting no reaction. I figured I was my usual non-shooting self. Then I went up to check the bottle - a bunch of little holes, mostly in a 2 inch circle. I'm so used to hitting them witn pistol bullets and seeing them fly, I forgot how they react to little high speed bullets.

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Replace the carrier key and the gas tube. If you shoot a lot of 3 gun you probably should do this every year like changing mag and recoil springs on your pistol.

Brownells sells a replacement kit for $30.00

231-000-045 Rifle Gas System Kit

When you replace the gas tube make sure you have proper alignment of the tube, gas block, and gas port on the barrel. If you have a adjustable gas block after replacing the gas tube and carrier key open it up all the way and then adjusted it down until the rifle will not cycled based on the ammo you are using, then you will know where to adhest up from for reliability.

If the problem is intermittment I bet you a dollar it is the gas tube and carrier key fit.

The problem is not the buffer spring, it is a gas problem.

Like I said in the above post it is a gas problem. I have had this very same problem that you are experiencing. Buy the above mentioned kit from Brownels. Invest $50 in the tools you will need and fix it yourself.If you do not have a buddy that can show you how to take the rifle apart,then buy the gunsmith institute video.

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+100 on just plain sendin' that suckah' to Benny, or Clark Custom. Those folks know AR's way, way better than any general smith. The last time I took an AR to a general smith was to get access to his tools so "I" could fit new parts in the trigger and get back into a match after a malfing trigger blew me outa' a stage. The local smith watched and just said Dang' I never knew dem' AR's worked like that! I sent it to Benny for a proper fix after my hack job got me through the rest of the match. Nuff said ;-)

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+100 on just plain sendin' that suckah' to Benny, or Clark Custom. Those folks know AR's way, way better than any general smith. The last time I took an AR to a general smith was to get access to his tools so "I" could fit new parts in the trigger and get back into a match after a malfing trigger blew me outa' a stage. The local smith watched and just said Dang' I never knew dem' AR's worked like that! I sent it to Benny for a proper fix after my hack job got me through the rest of the match. Nuff said ;-)

Benny Hill, Triangle Shooting Sports, 361-241-1091, Corpus Christi Tx.--------Larry

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Before you send this gun to a gunsmith, which will incur some expense and delay no matter who you use, I would suggest you attempt the repair yourself first. The AR15 is about the simplest rifle to work on for an amateur gunsmith. Parts are cheap, and most everything can be done with simple hand tools, a combination wrench and an action block (an investment you will use in the future - trust me). What you learn working on your own rifle will stand you in good stead for the rest of your shooting career. Sending the gun to a smith, while resolving the problem quickly, leaves you none the wiser. This is the "teach a man to fish" thing.

Have you exhausted all the advice in the posts above ? If the carrier key is secure on the bolt carrier, confirm that it also slides reasonably snugly on the end of the gas tube (remove the bolt, then slide the BC into the upper and feel the fit). After that, the gas rings would be a leading contender and are cheap/easy to change out. Have you scrubbed away all the carbon crud in/on the bolt carrier assembly ?

If everything else is tight, then I would suspect a partial misalignment between the gas port and the the front sight base. This is not so likely if it is a GI barrel, which FN would be, because the FSB is held in place with taper pins and the FSB gas port is bigger than the barrel gas port. I assume the FSB is not wobbly ? Gas port alignment could be a problem if the FN barrel were a QC reject (possible - FN supposedly do NOT sell M16 barrels to the civy market), or if someone has installed an aftermarket FSB/gas block that holds in place with set screws, and they did not align things properly. If you found the gas port to be misaligned, you could try realigning (with a set-screw FSB/gas block) or just replace the barrel with one from a trusted source.

If you run out of ideas here, I'd encourage you to try the guys over at the Troubleshooting forum on AR15.com... they seldom lose a patient :D .

Good luck !

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RevChuck,

Maybe I am in the minority here, but not all rifles like all ammo. Maybe there in nothing physically wrong with it, it just doesn't like the Remington stuff. I would never sway someone from sending it to TSS for a makeover, but I would stress test it with ammo that works first..

Mike

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