AR-15 Barrel Questions

[Sidewinder]

I just bought a, supposedly, brand new unfired DPMS complete upper yesterday from an individual. When I got it home and inspected the bore with a bore light, I found what looks like rust pitting in the area where the gas port was drilled into the barrel! Actually, this spot is so large it can be seen without a bore light.

I thought it was debris, and pulled a Bore Snake through it a couple of times. It was still there, so I ran a brass bore brush through it with some Hoppes No. 9 trying to remove it. It was still there, so I pulled some patches through, first with Hoppes and then just clean dry patches. The spot is still there. Assuming it is rust pitting, and I believe it is, will this affect the accuracy, being that the gas port is about half way up in the bore? Is it possible for it to start shaving material that would eventually restrict the gas port, and therefore the gun's operation? The person that sold it to me is working with me, at this time, to try to resolve the issue, as he built it.

One other question, about this upper. He said it is a 5.56 Mil Spec, but I can't find any markings to that on the barrel. Possibly, it's under the hand guards, but I haven't removed them yet. I tried, but apparently it's a two man operation with that pesky D ring. Suggestions on doing it solo, without the tool is appreciated.

Thanks for any help you guys are willing to share with this AR-15 newbie.

Edited April 14, 2010 by Sidewinder

[Guest 10mm4me]

If it is mil-spec the caliber and twist will be on top of barrel near front sight assembly. Can't imagine there is "rust" just there and nowhere else. May be built up fouling. Run a patch w/solvent through, let it sit, then run a .243 brass brush through a few times. Or just go out and shoot the hell out of it. That usually cleans it out good. Then clean it. If they are standard handguards the D ring may be a little stiff. That is however indicative of how new it is. If it is super stiff it may be as new as he said. There is also no such thing as unfired as everything gets test fired from the manufacturer.

Edited April 14, 2010 by 10mm4me

[Sidewinder]

If it is mil-spec the caliber and twist will be on top of barrel near front sight assembly. Can't imagine there is "rust" just there and nowhere else. May be built up fouling. Run a patch w/solvent through, let it sit, then run a .243 brass brush through a few times. Or just go out and shoot the hell out of it. That usually cleans it out good. Then clean it. If they are standard handguards the D ring may be a little stiff. That is however indicative of how new it is. If it is super stiff it may be as new as he said. There is also no such thing as unfired as everything gets test fired from the manufacturer.

10mm4me, thanks for your reply. I did all of the things you mentioned, and the irregular shaped spot is still there. I'm beginning to think it may be a factory manufacturing defect. It almost looks like the rough edges around a hole, when too much pressure is used, and the drill "breaks" through, leaving jagged edges, or possibly slivers breaking away from the drilled hole.

There are no markings on the barrel ( a 16" HBAR in 5.56 by DPMS) that can be seen without removing the hand guards. Don't know if there'll be any under there either. The rest of the bore cleaned up nicely. The only spot is around the gas port hole. I like this upper, but am concerned about problems with accuracy and functionality, if not now then later. Thanks again.

Would all you AR-15 guys and gals look down your bores and tell me if you have a big spot around your gas port hole? Many thanks.

[Wingshooter]

I can see the gas port if I hold the bbl just right. I don't see rough edges around it though. The stamp should be on top of the bbl forward of the gas port. What length handguards do you have? Carbine length handguards on a 16" bbl should not cover the stamp. If you have rifle-length guards on a 16" bbl, I guess it could be covered. I don't have that setup, so I can't say for sure.

To remove the D ring, I set the butt of the rifle on the bench and push straight down on the ring with both hands. Once it frees up, you can hold it in place with one hand and remove the lower half of the handguard.

Edited April 14, 2010 by Batman

[Westwindmike]

My factory built DPMS AR's barrel is marked on the bottom in front of the front sight. It says:

"DPMS CAL .223 1-9"

It's possible that he used a DPMS upper receiver and a no name barrel. Without markings, you don't even know what the twist is and therefore what weight bullets to use in it.

If you bought it as a "DPMS" upper, I think I'd be wanting some documentation as to where it came from or my money back.

[Guest HCRoadie]

It's possible that he used a DPMS upper receiver and a no name barrel. Without markings, you don't even know what the twist is and therefore what weight bullets to use in it.

You CAN discover the twist rate in a barrel that does not have that marked. Get your cleaning rod, slotted Patch holder/jag, and a patch. Get the rod with patch holder/jag started down the bore. Mark the 12 o'clock position on the rod, near the handle. Now slowly push the rod in letting it naturally spin with the riffling of the bore. Measure how far the rod went in when you see the 12 o'clock mark show back up at 12 o'clock. This will give you your 1 rotation per inch measurement. This can also be done with a bore brush. As for the alleged pitting or debri that you are seeing....I don't know. My AR-s look cleanly tapped.

Edited April 14, 2010 by HCRoadie

[R1100R]

I was told by DPMS all of their complete upper assemblies are test fired before they leave the factory. Same with S&W. My S&W was even delivered dirty.

[Westwindmike]

I believe the OP said the guy he bought from, "built it".

[Sidewinder]

Hey Guys, thanks for all the good information. I just took it to some AR guys that know their stuff, and here's whats wrong with it. 1. The gas port is drilled off center. 2. To compensate for that, someone wallowed out the hole with the drill bit, presumably to make it and the tube port align up. 3. What I'm seeing inside is in fact, not rust, but an elongated and buggered up gas port! 4. The gas tube is improperly installed at the A2 front sight base. The pin used is a roll pin that doesn't go all the way through the tube. It's believed it's in the wrong hole and that the gas tube is ruined too. 5. The hand guards were removed, and there is no... "none ...nadda" markings on the barrel anywhere. The barrel was sold to me as a 16" DPMS HBAR with an A3 flat top upper receiver. 6. None of the parts could be identified as DPMS. 7. There's tool marks where the front sight base pins were installed. I'm currently working with the seller to get my money refunded, or an acceptable complete upper, so I'm not using any names or details at this time. Rest assured, I'll let all of you know if there is an agreeable upper exchange, or my money refunded. Thank all of you that responded. I feel like I've been through the mill, but still want a good AR-15 to shoot paper and coyotes with. Thanks again.

Editing facts: The individual I bought it from said he bought it "built up" from another "parts guy" that sold him all his parts and moved out west. So, I'm not bad mouthing the skills of the seller... just the skills of whoever buggered up this nice setup.

Edit Update: Seller and I are meeting tomorrow to give him the gun back, and get my money back. I'll report back as this has been done.

Final Edit!!!! I just got back from returning the gun and getting my money back! Kudos to the guys at "On Target" for their expert opinions on the problems with the barrel and gas port/tube. I really appreciate you guys taking the time to look at it for me. And, they wouldn't take a penny for their time! We don't see much of that kind of service now-days. That's good old fashion service, and rare in these times where many are out to grab every penny they can get. Thank you guys at On Target very much.

MODS, can close this thread if they'd like. My money is back in my pocket.

Edited April 16, 2010 by Sidewinder
More facts.

[Guest OttoMaddox]

Glad to see that ended on an up note. Now whacha gonna buy?? I just got a bushmaster gas piston upper and I'm going to shoot it asap.

[Sidewinder]

Glad to see that ended on an up note. Now whacha gonna buy?? I just got a bushmaster gas piston upper and I'm going to shoot it asap.

Otto, just got a Bushmaster AR this weekend, and ran about 40 rounds through it today. I still want to build one, so I'm looking for a stripped lower from an individual... not an FFL. I'll probably buy a lot of the parts "online", and from individuals also.

Let us know how that Bushy piston power works. I'm a newbie, so I'm not familiar with the gas piston setup in the ARs. Is there an advantage over the regular setup? I'll probably just look for a complete upper instead of buying all of the individual parts.

Update Edit: Well. just traded the above mentioned Busy for another Bushy that'll meet my yote hunting needs, should punch paper nicely, and offers the opportunity to be shooting, instead of building! I believe it's a "keeper", and I can'y wait to get out tomorrow and shoot it. Like new... 40 rounds down the tube...yum yum!

Edited April 21, 2010 by Sidewinder
Update

[crashgordan]

"On Target" sounds like a great group!!!!

i'll start trying to use them!

[Sidewinder]

"On Target" sounds like a great group!!!!

i'll start trying to use them!

The guys were friendly, respectful.... they didn't treat me like a newbie, even though I am one, helpful...when another gun shop wouldn't even look at it...and...wouldn't take a dime for their time and expertise. Thanks again On Target.

[DaveTN]

I’m always leery of that. You see people that buy a DPMS or M&P lower and a bottom feeder rifle kit. Then it ends up in the for sale section as a DPMS or an M&P.

[Smith]

What's with all the red?

[DaveTN]

What's with all the red?

What red??