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Upper receiver gouging
- Thread starter McDuff
- Start date
WOW what caliber? Maybe part of the carrier key bent/loose screws? any marks on the carrier? what ever part is hitting the receiver should also have some kind of mark on it also? Is it over gassed maybe, and beating itself to death?
How far dose the bolt carrier move back before the buffer stops it? Should only be maybe 1/8-3/16 of an inch, behind the bolt catch.
What stock is on it? Im kinda thinking maybe your bolt is going to far into the stock before it is contacting buffer and being stopped, Dose it have a 308 rifle length buffer and spring in it?
Not sure about the carrier torking that much, the gas key should keep it from rotating to much, Unless all the parts are real sloppy? Should be able to rotate the carrier a tiny bit and still have clearance from anything on the carrier hitting the inside if the receiver. What brand of carrier? Is the firing pin retainer to long maybe? Just brain storming a bit here..... Something on that carrier is hitting the inside.
Not sure about the carrier torking that much, the gas key should keep it from rotating to much, Unless all the parts are real sloppy? Should be able to rotate the carrier a tiny bit and still have clearance from anything on the carrier hitting the inside if the receiver. What brand of carrier? Is the firing pin retainer to long maybe? Just brain storming a bit here..... Something on that carrier is hitting the inside.
Did you blow a primer? The spot where that gouge is located appears to be just above where the bolt carrier rail would ride.
Looks like something got caught between the carrier and the upper.
Looks like something got caught between the carrier and the upper.
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BROWNELLS 308 AR BUFFER | Brownells
Replacement Rifle Buffer for standard 308 ARs.
www.brownells.com
this is what i use in my 308 builds, with rifle length stocks.
I'll try that, I have a rifle length tube in shipping right now. It's deadlined until I make changes to it. After I solve the problem should I worry about the damage to the upper receiver?BROWNELLS 308 AR BUFFER | Brownells
Replacement Rifle Buffer for standard 308 ARs.
this is what i use in my 308 builds, with rifle length stocks.
An M4 length buffer tube with a stubby AR10 buffer would work correctly. If you have the wrong buffer in an AR10, it is too *short* and will bottom early. If you have an extended AR10 buffer tube and a stubby buffer, then it could go too far. Measure the length of your buffer tube and buffer before buying parts. If the buffer is 7", it's an M4. If 7.75" it's an extended AR10 buffer tube. Measure your buffer and compare it against one you've got on an AR-15.
This is what a stubby AR-10 buffer looks like that allows the use of M4 buffer tubes.
AR-308 Carbine Buffer : LUTH-AR LLC AR-308 CARBINE BUFFER | Brownells
Either you have an M4 7" buffer tube and a stubby buffer, or you have an AR-10 7.75" buffer tube and a standard buffer.
This is what a stubby AR-10 buffer looks like that allows the use of M4 buffer tubes.
AR-308 Carbine Buffer : LUTH-AR LLC AR-308 CARBINE BUFFER | Brownells
Either you have an M4 7" buffer tube and a stubby buffer, or you have an AR-10 7.75" buffer tube and a standard buffer.
Then you have a stubby buffer, or the bolt wouldn't come all the way back. It shouldn't be an issue of stroke then.
That damage doesn't look like galling or wear. That is spalling or impact. I'd keep running it and see how things progress, that is most likely from a single event that won't repeat.
If you have a 7" buffer tube, you can't over-stroke the BCG. If you had the wrong buffer with that tube, it would not allow the bolt to go back enough to strip a round from the magazine.
May want to fill in the marked parts with a sharpie marker and see if the wear continues. Just a thought
Check to see if you broke off some of your firing pin retaining pin.
It’s common in AR-10s for the FPRP to get bent or damaged from firing pin blowback inertia slamming into the pin.
There aren’t too many things that could cause those strange marks in that location. I’ve never seen anything like it, and I’ve seen some weird things in AR-10s and variants over the years.
It’s common in AR-10s for the FPRP to get bent or damaged from firing pin blowback inertia slamming into the pin.
There aren’t too many things that could cause those strange marks in that location. I’ve never seen anything like it, and I’ve seen some weird things in AR-10s and variants over the years.
What brand is the upper? Some uppers are cast and not milled. Looks like it could be a cast defect.
Nobody has made cast upper receivers in ages, especially for the AR-10.
There were some rare cast uppers for the AR-15 at one time, but they cracked regularly and never contributed to any significant numbers in the market.
DPMS used to make a cast lower receiver, but it was for a limited time. Marked “A-15 Panther Arms” with the selector stops at 90˚ from each other.
I’ve never seen a cast AR-10 imitation upper.
There are some cheap 6061 large frame uppers/lowers out there though.
You don't have to worry about that damage as long as there are no major cracks radiating from it. That is much less "damage" than what is being done to the skeletonized uppers on the market today.
The reason I thought it was cast is because the metal looks pores. If the damage was caused from several impacts, then I would look for an foreign object that was bouncing around. Do you have any scaring on the top of the bolt?
If you plan on running this upper there is only one way to stop cracks from forming or spreading and that is to drill them out. I would measure the deepest point and drill just past it.
If you plan on running this upper there is only one way to stop cracks from forming or spreading and that is to drill them out. I would measure the deepest point and drill just past it.
You ordered a .308 sized rifle length buffer as well ... right ? ( Needs to be 3/4" shorter then a normal AR15 rifle buffer. )
For large frame AR's.....
Your Aero carbine RE and buffer setup is a DPMS pattern carbine setup. Those use a 7" buffer tube ( normal AR15 carbine buffer tube ) and a purpose made 2.5" buffer length ( to allow for the extra travel of the longer 308 sized BCG into the buffer tube.
FWIW.... KAK sells a 5.3oz 2.5" buffer for your setup. ( MidwayUSA rebrands them as ARStoner )
The Vltor / Armalite Pattern uses a 3/4" longer buffer tube ( 7.75" ) that allows use of a normal AR15 carbine 3.25" buffer.
As mentioned.... the parts DO NOT intermix without causing issues.... confusing ? Yup...
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Phew....
FYI...KAK sells a 9.3oz one. ... and I believe MidwayUSA rebrands them... https://www.midwayusa.com/product/1021956833?pid=814615
2.5" KAK 5.3oz ....https://www.midwayusa.com/product/1021956650?pid=724762
Midway has them on sale frequently
Pretty sure the charging handle covers that part of the receiver , is there damage to charging handle ?
From the pictures it seems to be above the charging handle channel.
(upside down)
Look at picture 2 and you can see one of the notches for the CH to drop into.
Put some peanut butter in the dings and see where it ends up.
(upside down)
Look at picture 2 and you can see one of the notches for the CH to drop into.
Put some peanut butter in the dings and see where it ends up.
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HUH?? The charging handle rides in the square notch in the receiver, not the round part that the carrier rides in.
The marks are where the BCG is housed not in charging handle area.
In one of the pictures the BCG is in place and you can see the relation.Damage is above when receiver is upside down like in the picture.
I would feel the staking at the gas key, or look for a ding at the rear edge of the corresponding bearing surface on the carrier. It's not far enough around to be the retaining pin. Too many dings for a piece to hang around long enough.
Make sure the stock tube is not cross threaded driving the carrier up at the rear.
Cold blue the suspect areas on the carrier. Or black marker as suggested earlier.
Unpin, hand cycle with the carrier held up in the rear (or down if upside down )
Make sure the stock tube is not cross threaded driving the carrier up at the rear.
Cold blue the suspect areas on the carrier. Or black marker as suggested earlier.
Unpin, hand cycle with the carrier held up in the rear (or down if upside down
)
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If I had accidentally ordered an AR15 buffer assembly is there a chance that the buffer being too light, bottoming out in the tube and torquing the BCG to the side?
No. If you had an AR15 buffer you'd know it because the BCG wouldn't be able to cycle enough to strip a round off the mag or lock back.
Looking at it again, it appears more like factory tool chatter from a tool head that accidentally went in there and chattered around after bouncing off the inside, but the angle is just really weird for that to happen.
Especially since it happened after anodizing. It makes no sense.
Especially since it happened after anodizing. It makes no sense.
Looking at the pictures again it is not where I thought it was originally, you are correct.
Maybe no gouges... but maybe some scratches... just thinking out loud.
Those marks are in a very odd place.
Good to see it isn't reoccurring.
FWIW... if your upper to lower fit is loose... one of these might snug it up.
"
Will the shim tighten .308 upper receivers?
The shim does tighten .308 receivers that have the AR15 upper receiver recess/sear relief dimensions shown on the Installation Basics Page. "
http://www.wheeldiamond.com/ar15accushim.htm
FWIW... if your upper to lower fit is loose... one of these might snug it up.
"
Will the shim tighten .308 upper receivers?
The shim does tighten .308 receivers that have the AR15 upper receiver recess/sear relief dimensions shown on the Installation Basics Page. "
http://www.wheeldiamond.com/ar15accushim.htm
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