.22lr dedicated ar diagnosis?

[DVSride]

[DB>]

Sounds like some sort of alignment issue - maybe the mag is seating a little too deep, causing the bolt to scrape across the top of the following round as it cycles? Might be a burr on the bolt? Once "scraped", the damaged round might not feed as reliably, could be slightly out of round or have some brass sticking out a bit..

I had a gun doing something like you describe, can't for the life of me remember how I fixed it, but it must not have been too hard!

[AR22]

So is it just the CCI SV or you are experiencing the same malfunction with all ammo? Maybe try it without the SW Adapter in there and see what it does. Have you tried different magazines at all? May also want to try some sort of pressure plug in the buffer to give the bolt a little forward pressure.

[Garand Hunter]

Have you tried Blackdog mags ?

Psalm 1

[DVSride]

Sounds like some sort of alignment issue - maybe the mag is seating a little too deep, causing the bolt to scrape across the top of the following round as it cycles? Might be a burr on the bolt? Once "scraped", the damaged round might not feed as reliably, could be slightly out of round or have some brass sticking out a bit..

I had a gun doing something like you describe, can't for the life of me remember how I fixed it, but it must not have been too hard!

Actually that what I first though it was so I disassembled everything and deep cleaned it. When I handle cycled it ; no feeding issues but that was when I first noticed the lines on the bullet. Still need to test fire it to check actually function.

So is it just the CCI SV or you are experiencing the same malfunction with all ammo? Maybe try it without the SW Adapter in there and see what it does. Have you tried different magazines at all? May also want to try some sort of pressure plug in the buffer to give the bolt a little forward pressure.

Have you tried Blackdog mags ?

Psalm 1

Not yet, this is my only brand I have and I went with this because of the last rounds bolt back feature.

[mattt]

Black dog mags are the way to go only get the ones with steel lips not the original junk plastic

[AR22]

I love the SW 15 22 mags. None better for the AR22 platform in my opinion, and easy to load with the assist on the side. Not crazy about the SW 15-22 itself but love the mags. I do not use the adapter with them though. Last round Hold Open is not that important in my case. I add a shim of plastic epoxied to the front side of the SW 15 22 mag so it fits nice. I do love the Black Dog 50 Round drums. And I have two Sig Sauer straight 25 round mags too that are made by BD I believe. Or appear to be other than they have Sigs name on them. They function great too. Are you running any sort of pressure plug behind you BCG. You can buy one, or make one easy enough.

[oktavist]

It seems like the bottom of the bcg is scraping the top of the bullet when cycling the round. Is there a way to fix/prevent this?

This happens on all magazine fed firearms. Under normal circumstances, it doesn't cause any problems, and is infact required for proper feeding from a magazine.

Think about it. If there were no pressure pushing the round into the BCG, then there would be no pressure to push the round up infront of the bolt to chamber the round.

The only time this doesn't happen is when your mag is not fully inserted and the bolt fails to pick up a round.

[ThatFishGuy]

I would also check the edge of the chamber where the extractor cutout is. The hardened extractor claw can start to roll over the edge of the chamber, especially on the sleeved barrels like the Beyer. It happened to mine and I just used a machinist scraper to remove the but that had formed. Maybe give that a look

[ar15barrels]

It's completely NORMAL for cartridges fed from a magazine to rub against the underside of the bolt or slide that contains the cartridges in the magazine.
This is necessary because the spring under the column of ammunition in the magazine pushes the ammunition UP against the underside of the bolt/slide SO THAT when the bolt/slide retracts BEHIND the top round in the magazine that the whole COLUMN of ammunition can move UPWARDS far enough for the BOLT/SLIDE to strip the top round off of the magazine feedlips.

So, you can polish under the bolt/slide to reduce the contact damage, but you will never eliminate the contact unless you choose to single-load the chamber.

[DVSride]

It's completely NORMAL for cartridges fed from a magazine to rub against the underside of the bolt or slide that contains the cartridges in the magazine.
This is necessary because the spring under the column of ammunition in the magazine pushes the ammunition UP against the underside of the bolt/slide SO THAT when the bolt/slide retracts BEHIND the top round in the magazine that the whole COLUMN of ammunition can move UPWARDS far enough for the BOLT/SLIDE to strip the top round off of the magazine feedlips.

So, you can polish under the bolt/slide to reduce the contact damage, but you will never eliminate the contact unless you choose to single-load the chamber.

That makes sense. I did polished the bottom of the bolt and the marks are a lot less. I guess due to the CCI SV, the lead bullet really shows the scrapes vs the copper coated.

I would also check the edge of the chamber where the extractor cutout is. The hardened extractor claw can start to roll over the edge of the chamber, especially on the sleeved barrels like the Beyer. It happened to mine and I just used a machinist scraper to remove the but that had formed. Maybe give that a look

This happens on all magazine fed firearms. Under normal circumstances, it doesn't cause any problems, and is infact required for proper feeding from a magazine.

Think about it. If there were no pressure pushing the round into the BCG, then there would be no pressure to push the round up infront of the bolt to chamber the round.

The only time this doesn't happen is when your mag is not fully inserted and the bolt fails to pick up a round.

Very true, now that I think about it

I love the SW 15 22 mags. None better for the AR22 platform in my opinion, and easy to load with the assist on the side. Not crazy about the SW 15-22 itself but love the mags. I do not use the adapter with them though. Last round Hold Open is not that important in my case. I add a shim of plastic epoxied to the front side of the SW 15 22 mag so it fits nice. I do love the Black Dog 50 Round drums. And I have two Sig Sauer straight 25 round mags too that are made by BD I believe. Or appear to be other than they have Sigs name on them. They function great too. Are you running any sort of pressure plug behind you BCG. You can buy one, or make one easy enough.

Black dog mags are the way to go only get the ones with steel lips not the original junk plastic

Appreciate the info

[subscriber]

A real scrape at the "top" of the round, acquired on chambering sounds like a ding in the chamber mouth; probably from dry firing. Very easy to see, and easy enough to remove.

Does this setup have a functional empty mag bolt hold open? If not, the firing pin may strike the chamber mouth every time your mag runs dry. The 10/22 can be dry fired because it is designed for it, but in general .22 rimfire guns should not be dry fired.

You might still have a problem with the firing pin shape, that is able to deform the chamber mouth, right through the case. Unlikely, but possible...

If it is just a scuff mark, then the round dragging under the carrier is the probably (and completely normal) cause.