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ghost
01-08-2007, 9:30 PM
my ar wont chamber the rounds and its really annoying me .i went to the range and had to cock charging handle for every round it really sucked and started hurt my fingers,after shooting 120 rounds that day.when i cleaned my rifle i decided to shoot some clp in the gas tube to make sure it really was a leak/nothing blocking gas flow in tube and sure enough it leaked out of the gas block in between the handguard and the gas block.i might be wrong but thats what i think is causing the bcg not to cycle right?.any hints and input would be greatly appreciated.

Blacktail 8541
01-09-2007, 8:10 AM
That is porbably not your cause of problems, most gas tubes have a small leakaround the gas block. If your bolt is not cycleing a probable cause could be: 1. gas block not properly aligned or 2. If you built the upper yourself the gas tube was installed upside down.

Without more info it will be hard to find the specific cause.

ghost
01-09-2007, 9:06 PM
i dont know about either of those blacktail.i got the upper new and if the front sight/gas block wasnt aligned would me target area be off?it shot pretty accurate at the range that day 1" groups.i just want to fix this problem asap before i shoot again.it really sucked having to manually charge every round shot.please help me out guys!!!

Blue
01-09-2007, 9:23 PM
Do you have gas rings on your bolt? Can you take the entire bolt carrier group and everything out and post a pic?

ghost
01-09-2007, 9:53 PM
yeah i do have gas rings on my bolt.i actually had a fellow shooter at the range take my bcg out of the rifle and took it apart.he took the gas key out and checked the rings,he was stumped.is there anyway i could meet up with one of you guys here and actually show you my rifle?i`d appreciate all the help i can get.if any of you want you can pm me,thanks again!

kj
01-09-2007, 11:54 PM
Gas leakage around the front sight tower is common. The stainless barrel on my service rifle always gets a buildup of carbon there.

What Blacktail 8541 stated could be the problem. Although rare, the front sight tower may not be aligned with the gas port in the barrel. If it is not aligned with the port front-to-rear, it could cause the short stroking, and your sights would still be aligned on target. This can be checked with a small length of wire that is close to the diameter of the port. Put a 90 degree bend in the wire, insert it into the barrel, and if everything is aligned correctly you will feel the wire go into the port.

Short stroking can also be caused by loose gas carrier key screws. When I assemble my bolts, I apply some loctite to the base of the carrier key and the screws, torque the carrier keys screws to spec, then stake them. Check the carrier key screws. If they are loose, that could be causing your problem.

Did you assemble the lower or buy it factory assembled? Once in a great while, if the stock screw is torqued down excessively and the screw is a bit on the long side, it will protrude into your buffer tube. Upon recoil, the buffer will hit the screw, not allowing the bolt/carrier to come all the way back to strip a new round from the magazine. This is a common mistake made when installing an A1 buttstock using the standard stock screw. The standard screw is 5/8" too long. What type stock do you have? If it's an A2, loosen the buttstock screw a little to check it. Also check to make sure that the spacer between the tube and the stock is installed.

A buffer tube installed to deeply - butting into or over the buffer retaining pin will also restrict the bolt/carrier's backwards movement.

Even if you bcg is operating correctly, a bad magazine or weak mag springs will cause the next round not to be picked up when the bolt goes back. Is this an AW or an OLL?

Matt C
01-10-2007, 12:01 AM
Are you using the winchester Q3131 ammo?

My guess is a rough chamber causing FTE. Try some mil-spec M855 in it.

photog
01-10-2007, 10:14 AM
tons of info at ar15.com http://www.ar15.com/forums/forum.html?b=3&f=66

bwiese
01-10-2007, 11:04 AM
First, what kind of ammo are you using? Some of the Brit surplus ("British Aerospace" marked, in green vinyl bags) is notoriously anemic. Still, it cycles my ARs.

What kind (brand & style) of bbl/upper are you using, and are you using a standard A2 or F-marked front sight/gas block, or something else (aftermarket, railed, etc)? Is it staked or fixed w/screws?

While Win Q3131 is not as good as Win Q3131A, it *should* work in a properly operating AR. Fed American Eagle or Rem 'Yellow Box' 223 should work too.

If your front-sight/gas block fairly rapidly leaks a thick viscous liquid like CLP, that could be a problem. If it just stays in the gas tube for awhile before creeping out, that's more favorable.

BTW, it's not really good to clean/lube the gas tube. Now that you've put crap in there, you'll have to clean it out so it doesn't bake in there during subsequent firing - use something like aerosol BraKleen brake cleaning solvent and purge the hell out of it, and then blow it out w/compressed air. Don't use pipe cleaners, etc - crap gets stuck & burned into the gas tube and people wonder what's wrong after their rifle fails. Let the high-pressure hot gas do its work :)

I have a variety of factory Colt and Bushmaster bbls and run them w/a variety of ammo, and do not get any appreciable carbon fouling around the gasblock/bbl interface or gas tube/gas block interfaces even after a lot of shooting. A slight amount of leakage/buildup may be OK but if you're getting really cruddy there, it's a problem.

Gas leaks can also happen around the carrier key due to lack of (or poor) 'staking' and can cause cycling issues.

Try some different ammo, and also try a different bolt/carrier (borrow a friend's).

ghost
01-10-2007, 5:41 PM
my upper is an standard a2 upper and lower is a oll.i was shooting remington 55 gr mc that day.i`ll double check the buttstock screw and also the bcg again,maybe check the front sight alignment also.if i cant fix this issue i might have to take it to a gunsmith.thanks for the insights guys!!!

Blue
01-10-2007, 6:49 PM
How far does the gas tube stick into the upper?

ghost
01-10-2007, 6:55 PM
its flush with the receiver,sticks in the hole and doesnt stick out of the hole.

kap
01-10-2007, 7:00 PM
That doesn't sound right. It should protrude into the inside of the upper about an inch.

First picture shows the tube inside of the upper and the second shows the carrier with the tube inside of it.

Tzvia
01-10-2007, 7:19 PM
its flush with the receiver,sticks in the hole and doesnt stick out of the hole.

So you don't see a chrome tube jutting into the receiver when you take it off the lower, remove the bolt and charging handle and look in from the underside? If not that is the problem. That gastube should enter the front hole of the 'gas key' which is that tube sticking out of the bolt carrier, when the bolt is closed. Gas from the barrel travels through the gastube and into the bolt carrier through that gas key, unlocking the bolt and driving it back.

Blue
01-10-2007, 7:22 PM
So you don't see a chrome tube jutting into the receiver when you take it off the lower, remove the bolt and charging handle and look in from the underside? If not that is the problem. That gastube should enter the front hole of the 'gas key' which is that tube sticking out of the bolt carrier, when the bolt is closed. Gas from the barrel travels through the gastube and into the bolt carrier through that gas key, unlocking the bolt and driving it back.


What he said. Sounds like you might have a carbine tube in a rifle length upper. How long is your barrel?

ghost
01-10-2007, 9:47 PM
i have a 20 inch barrel.i guess that might be the problem,can i buy a replacement gas tube(rifle length)?thanks for the info guys!

kj
01-10-2007, 9:59 PM
If the gas tube is not protruding enough into your upper to make contact with your gas key, then that is definitely a problem. To replace it, remove bcg, take off the handguards, and use a suitable punch to remove the roll pin in your front sight tower that holds in the gas tube. Replace tube, reinstall roll pin, handguards, bcg and you should be good to go. Where did you get the upper. They should fix it, or at the very least send you a correct length gas tube. I've never heard of an upper that came with a too short tube.

Gringo Bandito
01-10-2007, 10:04 PM
i have a 20 inch barrel.i guess that might be the problem,can i buy a replacement gas tube(rifle length)?thanks for the info guys!


You can purchase them.

http://www.bravocompanyusa.com/Gas-Tube-s/45.htm

ghost
01-10-2007, 10:18 PM
sorry guys,i just opened up my rifle and checked out the tube and it is protruding into my bcg.so know i`m at a stand still to see what is wrong with it again.i also checked my buffer tube screw and its tight but not over tightened,checked the alignment in the barrel too.i`ll be at the chabot range this weekend and i hope i bump into one you guys there so you can check my set up.

Matt C
01-11-2007, 12:21 AM
Try different ammo (some milspec, bit hotter and fixes some problems) and shoot a few hundred rounds through it to break it in. That will fix 90% of problems right there.

PistolKidd
01-11-2007, 1:37 PM
Like anything, you need to determine what your problem is before you start mucking wiht it.

Gas leak or not, that may not be a true issue. As a lot of people here have stated, a small bit of leakage is normal.

I would try and eliminate as many variables as possible. Meaning grab different magazines, good ammo, and if you can another AR that you know works. Ideally, using super hot ammo isnt a great solution as your gun should feed anything reliably..

Try this, take a good magazine and load one round into it. Shoot it and see if it manages to lock the carrier back. If it does, gas leakage is not a problem as the bolt is traveling as far back as it needs to.

If it doenst lock back, then you can start looking at the gas system or something else keeping your BCG from moving far enough back..

If it does lock back, then something else is giving you failure to feeds. Magazine or perhaps the buffer spring itself. I had trouble with this and discovered that it was my hammer interfering with the forward motion of the BCG.. I readjusted it and now everything works fine..

kj
01-11-2007, 9:07 PM
vern - re-read my first post. Many feeding problems are due to bad mags. Since you have an OLL I don't know how much control you have over the mags being used. In my experience, I have found that the USGI mags are the most reliable - but I don't think that you have that option. Try some of the different ten rounders. Also, you can try taking your mag spring out and stretching it. If it works, then the spring is your problem.

Did you check the gas key screws?

PistolKidd brings up a good point. With one round in the mag, does it lock the bolt open after firing?

Sorry that I can't be of more help. I have a lot of experience with ARs, but not OLLs.

ghost
01-11-2007, 9:13 PM
thanks for the info guys.i checked the gas screws and theyre tight,i`ll have to try different mags also.maybe i`ll do the one round and see if it locks the bolt back.hopefully one of these should be the fix,if not i dont know what else i can do.i`ll keep you guys posted once i do these things and let you know what the outcome is.