AR Barrel Bore Pin Guage

[markm]

Great, now I'm going to have to pin gauge all my rifles.

Thanks MarkM.........

I may not have the experience to read this situation correctly. It's surprising that so many barrels stick right at that first inch of rifling. And I don't mean a little resistance. The gauge has to be reversed by tapping it with the cleaning rod to get it loose.

[markm]

dumb remark here, but are the barrels clean? That can make a big difference ime

Both Colts were dirty from shooting on Sunday. The Minnies was thoroughly cleaned since I was possibly going to run the reamer in that chamber.

[bobcatdriver]

I may not have the experience to read this situation correctly. It's surprising that so many barrels stick right at that first inch of rifling. And I don't mean a little resistance. The gauge has to be reversed by tapping it with the cleaning rod to get it loose.

I didn't read this right the first time. The gauge will not pass through at all without force? You do have to reverse it? That would be disconcerting.

[markm]

I didn't read this right the first time. The gauge will not pass through at all without force? You do have to reverse it? That would be disconcerting.

Correct. My psycho side wants to pound that fukker through. Hard to see from the upper receiver, but that all appear to have about a 1/2 inch of rifling visible where the gauge stops. I'm pushing the gauge from the muzzle back towards the chamber.

[Dr Dues]

Just pinned all my AR barrels. Only the Colts pass the gauge all the way through with no resistance. A Sabre 14.5 middy will pass it with some force.

Most of the barrels stick about 1" into the rifling. That's curious. I'm wondering if that part of the rifling gets roughed up with wear. Both Colts are relatively new barrels.

Copper and Carbon accumulation....I don't see what else it could be!??

It seems a tighter bore would show signs faster along with a shorter lead??

What do you think Mark?

[markm]

Copper and Carbon accumulation....I don't see what else it could be!??

It seems a tighter bore would show signs faster along with a shorter lead??

What do you think Mark?

Not sure. I'm no barrel expert. I really don't want to go down the bore scope worm hole. I was guessing maybe some fire cracking/roughing of the first inch of rifling raises some material on the lands?

At this point, I'm still thinking of adding the reamer to remove all chamber concerns in all my non-Colt barrels. If only the Minnies barrel failed the pin gauge, I'd consider the case closed, but now I'm still puzzled.

[Todd.K]

Many barrels are not as straight as most people would think.

I expect that you may be measuring copper buildup, and maybe some less than straight barrels.

[markm]

Many barrels are not as straight as most people would think.

I expect that you may be measuring copper buildup, and maybe some less than straight barrels.

I'm going to try a copper removal on the Minnies tonight! Thanks!!

I remember seeing FN's machine that straightens barrels that failed their pin gauge. Scary.

[triggerjerk]

I remember from somewhere that .22 lr's are reputed to develope a carbon ring just in front of the chamber you are supposed to deliberately attack every now and then. Don't know about centerfire....

[markm]

Carbon ring in centerfire is in the leade area I believe. This gauge wouldn't catch that. But I did try cleaning the hell out of the barrel.