RimX firing pin channel marking next round

[3jh]

I am seeing some marking on the next round up in my Magazine with my Rimx. I have had no failure to feed or eject with the stock rim-x magazines, and the accuracy is good, but I wonder if it could be better if the bolt firing pin channel wasn't marking the next round and all subsequent rounds in the magazine. The very first round chambers and extracts with no markings at all.

I've discussed with Zermatt and the gunsmith that did my barrel, and it is a reported as a normal occurrence and can be reduced some with polishing the bolt and or reducing spring pressure in the magazine.

Has anyone else seen and addressed this potential issue.

 

[DownhillFromHere]

Yes it's normal and yes there's an easy mitigation. Go to an auto parts store and pick up a pack of wet-lap automotive sandpaper (or get it from Amazon). A variety pack with grits as fine as 2000-2500 is less than $10. Use 1000-1500 grit to smooth the edges of the channel, then finish with the 2000-2500 grit.

It's impossible to not leave fine marks on the top bullet in the magazine as the bolt cycles, but I used this process on my bolt and reduced the marks noticeably.

Edit: I'd personally recommend against reducing spring pressure because it's too likely to induce failures to feed. I have a Zermatt/RimX 5-round magazine extender, which does NOT ship with a heavier spring. The stock 10-round spring usually feeds rounds in the extended mag ok (actually loading those last few rounds is a pita) but I have had too many failures to feed with the extension in place to trust it in a short-par match.

 

[3jh]

Thank you for reply. Is the intent to reduce the height of the firing pin channel, smooth and polish the exposed edges of the channel, or both? Did you do any polishing to the inside edges of the channel or only work on the outside edges.

Thanks again.

 

[justin amateur]

Are you sure it's the bolt?

The marks are typical of most magazine fed 22lr.
The top bullet, as it is pushed from the magazine into the chamber,
scrapes across the cartridge below it leaving drag marks.
The stiffer the magazine spring, the harder the bottom cartridges
press on the cartridge above them, causing those contact marks.
In severe cases, dragging a deep groove into the bullet beneath.

It's why hand feeding one cartridge at a time into the chamber
is considered an accuracy improvement tweak.
No damaged bullets.

 

[DownhillFromHere]

All you're doing is polishing the edges of the channel, nothing more. Any part of the channel that contacts the bullet.

Think logically about how the magazine works with the receiver and bolt. The magazine spring pushes the cartridge column upward, and the bolt HAS to run across the bullet. There is no way for the firing pin channel to NOT run across the bullet. So the best you can do is polish the channel edges.

Justin, he's seeing marks from the bolt. I know exactly what he's seeing because I see it too and I made certain it was the firing pin channel leaving the marks (two fine lines side by side) - but I see marks less after polishing.

 

[justin amateur]

Gotcha...

 

[3jh]

All you're doing is polishing the edges of the channel, nothing more. Any part of the channel that contacts the bullet.

Think logically about how the magazine works with the receiver and bolt. The magazine spring pushes the cartridge column upward, and the bolt HAS to run across the bullet. There is no way for the firing pin channel to NOT run across the bullet. So the best you can do is polish the channel edges.

Justin, he's seeing marks from the bolt. I know exactly what he's seeing because I see it too and I made certain it was the firing pin channel leaving the marks (two fine lines side by side) - but I see marks less after polishing.

 

[3jh]

Thanks again for the interest and help with the issue.