I have a question, should there be carbon fouling on the top of the barrel behind the gas block? I tried to tighten it and it is TIGHT! This rifle went from shooting consistent .5 MOA with three different bullet powder combinations to 1.5 MOA with the same loads virtually over night. I thought maybe it was a scope issue. Changed out the glass and the same thing. The barrel appears tight. Any help would be appreciated.

PaPa 260

A little carbon leaking is nothing.
Sudden poor accuracy would most likely be due to a worn out barrel or a loose gas key.

Make sure the gas key screws are tight & staked.

How many rounds do you have through the barrel. Anything over 3,500 rounds is really a gift.

One more - is the muzzle damaged? Take a Q-Tip and run it around inside the muzzle. If it catches on anything you need to re-crown.

Hello,
I have the same rifle and would assume yours is the SS 1/8twist barrel, 20", w/ slotted/picitinny gas block?? Mine has given excellent service and accuracy for some 4 years now and when you say you attempted to tighten are you talking about the allen head screws which clamp/secure the gas block to the barrel?? As a thought, could you have rotated the block slightly out of alignment causing an incorrect path for the gas in the tube?? Not likely that happened, but just a thought. As mentioned by others, I would not worry about the "leakage" of the gas in that area for it is not uncommon. If you can get them to answer the phone, factory people can give you proper torque for the gas block and further advise on your accuracy problem. Good luck.

martin

I appreciate the response. This barrel has less than 150 rounds down the tube and has been cleaned every time I shoot it. The crown is in good shape, I checked that. What are you calling the gas key screws? What is common fouling? This barrel has carbon fouling on it for nearly 5" behind the gas block? Yes we have the same rifle it soundsl like. MFD does yours leave any fouling on the top of the barrel?

I did finally talk to a human at Armalite late this afternoon. I bought this rifle from The Match Armores Shop near me. The fellow at Armalite told me to take it to him. He does work for Armalite. He is on his way back from Colorado now, and will be in later tonight. I am going to take it to him tomorrow. That was my first option anyway, he just wan't there so I called Armalite. Geoff builds his on AR's and those for other shooters for across the the course competition. He is a Distinguished High Master with a service rifle and knows his way around them that is for sure.

I am 57 years old and have never owned a semi auto anything before this AR. I have always had bolt action rifles, pump shotguns and revolvers. I really do like this rifle, I just have no knowledge of it. Again I appreciate the responses!

Do you gentlemen hunt with yours? I am thinking this rifle would be a pretty darn handy coyote rilfe.

PaPa 260

The wife and I have shot several turkeys with AR type rifles, and I have shot javillina with them as well.

I have killed 2 deer with a 223 but I used a Steyr AUG, and I have shot prairie dogs with an AUG and an AR as well.

My DPMS barrel has two little dimples on the underside of the barrel for the setscrews under the gasblock. Makes locating it and gettin' the screws tight really nice. I just take my allen key set and torque them little screws down as tight as I can get 'em. The setscrews on the gas key are the two screws atop the bolt carrier-- the ones securing the "snorkel" (aka the gas key) to the carrier. They have to be tight or there will be insufficient gas to cycle the action. I have gas fouling on my barrel, too. It doesn't go back five inches. That seems excessive to me. Sounds to me like the hole in the gasblock is too big for the gastube. That would be unusual for a factory ArmaLite gun...

Papa260,
I pulled mine out of the rack to further inspect regarding "blowby" and there is none.
I only recently put some 25rnds through it and cleaned as normal. I have built several AR15's over the years and yes, some do have the residue you are noticing, but does not seem to alter accuracy. Another thought is that if you look at the gas block, the gas tube inserts from the rear(breech end) and a small roll pin is drifted horizontally to retain the gas tube in the block. Can't imagine how, but if that roll pin has been moved/gone, the tube would tend to move about some and definitely cause leakage and even cease to function for the gas would discharge other than down the tube which actuates the rearward motion of the bolt/carrier.
As for Armalite rifles, for the money believe they are as good as you can buy and the fellow who has the Dist./HM in Serv. Rifle rating, that's about as good as it gets also so I would say you are in good hands. I shoot NRA Long Range w/ my Armalite, rating HM, and the rounds it takes to get those ratings will definitely give you opportunity to discover all manner of problems and solutions. If you have not done so, might take the time to visit one of your local clubs where they shoot Across The Course(XC) and see the skill it takes to attain High Master in Serv.Rifle. It "aint easy."

MFD, congrats on your HM rating. You are right that is NOT easy! While he was rebarreling a 788 Rem. for me back in 03 he invited me along to watch an XC match he and his wife were shooting in. He had told me they shoot out to 600 yards with AR 15's and battle sights. I thought but didn't say it, yeah shoot at it is all you do. I was impressed with the 200 yard off hand shooting, as well as the 300 yard rapid fire. But as I was looking through a spotting scope while he shot the 600 yard string. I truly could not believe what I was seeing. He finished that string with 200-9X. His wife was not far behind with a 198-7X. It so impressed me that I haven't forgot the scores. Shortly there after he built my first competition rifle to shoot F Class. I know one thing shooting XC is not for sissies! I haven't been able to shoot for the last year because of rotator cuff rebuild. Hopefully I will be able to get back into next year if this darn shoulder ever gets right.

PaPa 260

MFD, PM sent.

PaPa 260

i don't if you are still have a problem but i work on ar15 all day that have had 100,000s of rounds fired though them. make sure when you clean you Ar the gas tube is up the gas block and tube will get gummed up. as long as you got enough gas pressure to cycle the weapon that is probably not your accuracy issue.do you have handgards with a rail system on them, if they are the ones with an allen head screw you need to very careful put then on out of the 300 or 400 people have had me look at most have fail barrel straightness. ar15 can not take any pressure on the barrel.

Not to speak for Papa260, but he had further conversation with Armalite and had a faulty barrel in the gas port of the barrel itself and Armalite is taking care of the matter. He can give you all the details if he chooses, but good to know that Armalite backed up their product. I have same upper and has given excellent performance for quite a while now and
is equal to better than some custom built match 15's I have had over the years. Good gear all around.

martin

quote:

Originally posted by MFD:
Not to speak for Papa260, but he had further conversation with Armalite and had a faulty barrel in the gas port of the barrel itself and Armalite is taking care of the matter. He can give you all the details if he chooses, but good to know that Armalite backed up their product. I have same upper and has given excellent performance for quite a while now and
is equal to better than some custom built match 15's I have had over the years. Good gear all around.

martin

I've never known Armalite not to take care of their customers, their service is outstanding, as are their rifles.