PDA

View Full Version : Help a noob! AR 10 messed up feed ramp and bolt (pictures)


connorr93
05-26-2012, 2:27 PM
So I purchased a AR 308 used and took it out for a test fire about a week ago. (fired about 40 rounds). When I was cleaning I noticed this.

http://i757.photobucket.com/albums/xx215/connorr93/IMG_0261.jpg
http://i757.photobucket.com/albums/xx215/connorr93/IMG_0260.jpg
http://i757.photobucket.com/albums/xx215/connorr93/IMG_0259.jpg
http://i757.photobucket.com/albums/xx215/connorr93/IMG_0258.jpg
http://i757.photobucket.com/albums/xx215/connorr93/IMG_0257.jpg
http://i757.photobucket.com/albums/xx215/connorr93/IMG_0255.jpg

It appears there is a chunk out of each corner of the BCG and some nicks on the feed ramp. How bad is this? Is it ok to continue to shoot? Does my BCG need replacing?

daybreak
05-26-2012, 2:33 PM
http://img.tapatalk.com/475c448d-4c09-45a6.jpg

the locking lugs are def chewing up the non-ramped receiver.

daybreak
05-26-2012, 2:35 PM
was the damage there when you inspected the rifle before buying it?

Intimid8tor
05-26-2012, 2:36 PM
I'm not an expert on headspace, but it seems the bolt is not able to get all the way in and lock. The ramping of the receiver (or lack thereof) seems to be in the ok camp on the pic above.

What would cause the bolt not to go in all the way and lock completely?

Redchevyman
05-26-2012, 2:42 PM
I would not shoot that. It looks like it fired with partial lock up. The inside of the barrel extension may have matching damage to the bolt head.

I would replace the bolt head and barrel extension before firing again.

Hoop
05-26-2012, 2:45 PM
You need to cut some feedramps in the receiver. You can do it with a dremel. It's ugly but it'll work 100%.

Hoop
05-26-2012, 2:46 PM
I would not shoot that. It looks like it fired with partial lock up. The inside of the barrel extension may have matching damage to the bolt head.

I would replace the bolt head and barrel extension before firing again.

Very possible as well.

FMJBT
05-26-2012, 2:50 PM
I'm not an expert on headspace, but it seems the bolt is not able to get all the way in and lock. The ramping of the receiver (or lack thereof) seems to be in the ok camp on the pic above.

What would cause the bolt not to go in all the way and lock completely?

Headspace might be short, or it could have a really tight chamber with some dirt or carbon in it preventing full lockup. Either way, that can be a pretty dangerous scenario weaiting to happen. AR's are not supposed to be able to fire out of battery, but it has happened on occasion. I think the bolt itself is done. Couldn't pay me enough to stick my face next to that one and pull the trigger kind of done. Definitely get a replacement for that, as well as having the lugs on the barrel extension inspected and headspace checked by a competent gunsmith using the replacement bolt.

G-forceJunkie
05-26-2012, 3:12 PM
The lack of m4 ramps on the reciever have nothign to do with that damage. That bolt is not safe to fire. I would guess that bolt my not have been properly heat treated for that much damage to happen in 40 rounds or it fired not fully in battery. Whos bolt is that?I would inspect the back side of the barrel extension for damage or bad machining as well. Were you having any trouble withthe bolt going fully into battery? It looks like it was able to fire with the bolt not rotated all the way into battery and it tore the edges off. Something is not right, do not fire that weapon untill you have figured out the problem.

connorr93
05-26-2012, 3:23 PM
Ok guys Im brand new to this hobby and truthfully I dont understand most of whats being said. Heres what I understand so far about how the gun operates.

When I shoot, the Bolt carrier group shoots forward into the barrel extension (i think thats what its called) and twists behind it. From what I have gathered the bolt head is not twisting far enough behind the barrel extension and therefore not locking up before shooting. As for the nicks in the upper receiver I have no idea how that happened. Is the bolt head hitting it on the way in? I can operate it manually and I cant see how thats possible. Thanks for the help!

G-forceJunkie
05-26-2012, 3:48 PM
Correct. Something is messed up with the bolt rotating fully. The chamber may be machined undersize, or the ammo is oversize. Please give us ALL the information: What ammo, factory or handloaded? What barrel, what bolt, is that a factory upper or one you put to gether? Was the headspace checked with a gauge? That covers the big saftey issues. The dings on the upper where the bullet hits when it feeds is because you have mis matching parts: The upper does not have the "M4" style cuts that your "M4" style barrel extension is machined for. Generally it is fine, if the rounds were feeding properly, i would not worry about it. The damaged bolt is your problem and that needs to be addressed and the bolt replaced, and the original problem fixed. Where are you located?

Panchira!
05-26-2012, 5:56 PM
I think when the previous owner of that rifle never head spaced it when he built it. Either way do not shoot it. If you are uncomfortable diagnosing it take it to a gun smith. Something is seriously wrong with it.

gunnerstuff
05-26-2012, 7:09 PM
Looks like the damage is occurring after the firing as the bolt is rotating to unlock. Also as mentioned before, the bolt lugs do not look like they have been heat treated properly.

What ever you do, DO NOT FIRE IT any more!

Sky_DiveR
05-26-2012, 9:02 PM
I also think it's a head space issue and that the bolt is now garbage. Replace bolt, inspect the barrel extension (which from the pics looks OK), and have the head space checked. Also don't fire it until these issues have been addressed.