PDA

View Full Version : Normal wear on my new AR bolt lugs?


Eric B
02-02-2013, 4:16 PM
Short and sweet....

New AR build. Bolt catch is grabbing shallow with my new BCG, but bites good with an old BCG installed in the new build.

NEW BCG IN NEW BUILD. (http://i.imgur.com/CvEP29J.jpg) See the very shallow catch?

OLD BCG IN NEW BUILD. (http://i.imgur.com/qXclZlX.jpg) See the much better bite?

New BCG is bad? I dunno. When I put the new BCG in my old rifle, it grabs pretty good. NEW BCG IN OLD RIFLE. (http://i.imgur.com/m8HEFev.jpg)

WTF is going on there? Wait, there's more.

The lugs on the new bolt are taking a beating. After the build was complete I lubed up the new BCG/bolt and manually cycled between 100-200 times. Check out the wear on the 11 o'clock and 1 o'clock lugs.

LUG WEAR 1 (http://i.imgur.com/5klH4ft.jpg) New BCG is on the left.

LUG WEAR 2 (http://i.imgur.com/gXu8L3n.jpg)

The breech face on the new upper doesn't seem to be taking a beating. It looks good to me.

NEW UPPER BREECH (http://i.imgur.com/GQk5FZi.jpg)

ANOTHER ANGLE (http://i.imgur.com/qKkO3Bv.jpg)

When I remove the CH and slowly slide the new BCG into the new build upper, its smooth like butter and mates up beautifully, so why the wear? Is it going too deep?

Why is my new bolt catching in an old gun, but not the new build? Why is an old bolt catching in the new build just fine?

Any help is appreciated.

6mmintl
02-02-2013, 5:03 PM
Did you burr the bolt catch with the roll pin during installation? causing drag on bolt catch and receiver slot for bolt catch?

I usually stone smooth the bearing surfaces on bolt catches for free unrestricted/no drag operation.

Eric B
02-02-2013, 5:07 PM
Did you burr the bolt catch with the roll pin during installation? causing drag on bolt catch and receiver slot for bolt catch?

I usually stone smooth the bearing surfaces on bolt catches for free unrestricted/no drag operation.

The bolt catch seems to function just fine. It's smooth and travels freely. It catches good and deep on my old bolt, but it's shallow on the new bolt. So shallow that a light bump of the gun sends it home. It's too fickle.

What do you think about that upper lug wear? It seem to be wearing past the "coating" and into the metal itself. Do bolts sometimes ride high? Is that a thing?

ar15barrels
02-02-2013, 6:09 PM
Does the new bolt have some wonder finish that makes the bolt more slick?
The slick finish fights against the ability of the bolt catch to retain the bolt.

Eric B
02-02-2013, 6:14 PM
Doubtful. It's the bottom of the line AR Stoner (http://www.midwayusa.com/product/145235/ar-stoner-bolt-carrier-assembly-mil-spec-ar-15-223-remington-parkerized) (Midway USA store brand) BCG.

Even if it was "alien slick", why would it catch so shallow in my PSA upper and catch well in my Franklin Armory upper.

It makes my head spin. The BCG and the upper just don't seem to like one another.

L4D
02-02-2013, 6:20 PM
the pic of NEW BCG IN NEW BUILD looks like the carrier is tilted upward?

probably out of spec. The reviews are terrible.

Eric B
02-02-2013, 6:28 PM
the pic of NEW BCG IN NEW BUILD looks like the carrier is tilted upward?

probably out of spec. The reviews are terrible.

Why would it tilt upward in one rifle and seem to catch just fine in another? That's why its so perplexing.

Is the Franklin Armory bolt just so good it works well in either gun?

Is the Franklin Armory upper so much better than the PSA upper that it allows the ****ty AR Stoner bolt to function?

If there was other rubbing it would help me out.

Eric B
02-02-2013, 7:18 PM
For anyone following, or a future calgunner doing a search for a similar problem, its the lower.

Swapping the lowers between the uppers, and bolts between those, its come down to the built lower, which I made from an 80%. Something is alittle off and its keeping the lower a little too low. The bolt catch system may be machined just a little high, or not deep enough on the side to let the catch go in far enough.

More experimentation to follow.

kcstott
02-02-2013, 7:26 PM
How about the position of the bolt catch pin hole.
Thats a damn long drill and without a guide it will walk any direction it wants.

Eric B
02-02-2013, 7:31 PM
No idea right now, but fully possible. It's back in the safe until tomorrow when I have more time to disassemble and dive in. My fingers are raw from pushing, pulling and squeezing things.

Bad forging, out of spec 80% milling, duracoat thickness throwing things off, etc, etc , ... Hopefully I figure it out tomorrow.

paratroop
02-02-2013, 9:05 PM
I had that problem on my last build. I sprayed the alumahyde a little thick near the bolt catch and the mag catch, had to basically carve out the excess for either one to function 100%. The worst part about it is that little pin is the most difficult part on the entire lower.

On another note, I had the bolt stop jammed up one time, still can't figure out exactly how that happened.

Also I had a similar problem when using a nice billet upper once, it was actually machined jacked up. It didn't have that little cut out portion done right, not so nice after all.

kcstott, I think most 80%s have that hole already drilled out nowadays.

Eric B
02-02-2013, 9:26 PM
The mag release and bolt catch systems come finished as part of the 80%. I don't hear a lot of problems from these areas on 80%'s so...

My Duracoat was causing some issues with my mag catch. I had to shave a little there so I'm putting money on my Duracoat job causing my bolt catch issues too. I just hate that damned tight tiny pin.

I'll update tomorrow so others that know how to use CalGuns fickle search feature may save themselves stress in the future.

Eric B
02-03-2013, 12:40 PM
I pulled two bolt catches to compare to the one that wasn't catching.

One that works well in my Franklin Armory, and a new one from an LPK I have. My failing bolt catch was not the same size. I pulled out the Dremel and took about 1/32" off the back side.

It pushes in to the correct depth now, thusly raising it to the correct height, and all seems well with the world. Hallelujah! I hope this may be able to help someone in the future.

kcstott
02-03-2013, 3:51 PM
Well they are mill spec parts. Which means they were made by the lowest bidder:43::43::43:

Eric B
02-03-2013, 3:53 PM
Well they are mill spec parts. Which means they were made by the lowest bidder:43::43::43:

Agreed.

Eric B
02-06-2013, 9:02 PM
A little follow-up...

Four rounds. That's how many I got off before it stopped cycling. I pulled the BCG and sure enough the bolts had turned and the key was loose. A little elbow grease and it fired the next 150-200 rounds flawlessly.

stitchnicklas
02-06-2013, 9:43 PM
so.............
dremel to the rescue...AGAIN.

amazing tool,used one on a chiappa upper were the bolt was damaged,ramp
gunked and the chamber nicked. 3 dremels and flawless again

sharxbyte
02-06-2013, 9:59 PM
just watch for chipped/cracked lugs. I've busted 2 bolts in my rifle, and fortunately had no other components damaged. Then i bought a different bolt.

Eric B
02-06-2013, 10:14 PM
EDIT:

I lied. After cleaning off dirty oil and carbon I'm seeing severe wear and even some small bulging on the BACKSIDE of the bolt lugs on the bottom. Damn it. My brass looked good. From what I've read it looks like too much head space.

San Jose gunsmith suggestions? Its time for a pro to check it out.

Eric B
03-20-2013, 6:00 PM
Just an update for those that may search this in the future....

My bolt was ****! I swapped it out with a bolt I got form GunBroker that had thousands of rounds on it and it functions flawlessly with zero wear on the bolt. At least Midway said they'd swap it out when they get more in, if I want.