Knurled Slugs

[Spacebus]

After experimenting with different melt alloys and powder coating I finally got my .249-39 cast slugs up to an acceptable size for my Eagle Claw by knurling them and then sizing to .250" with an NOE sizer (actual size is closer to .2505" at the largest). I just used a random file I had laying around. Now for my question.

Is there a "proper" file for knurling bullets? I just rolled the slugs across a rough cut board with my file. I chose the best looking slugs for the photo below, not all of them have such a nice pattern. Would a more rough/coarse file give me deeper "voids"?

[Spacebus]

I also realized this might not be the appropriate child board.

[Firewalker]

A new flat rasp on a piece of thick suede would put the most knurl on those slugs but would it be too aggressive?

[Spacebus]

A new flat rasp on a piece of thick suede would put the most knurl on those slugs but would it be too aggressive?

The file I used was fine, but not as fine as a flat raker or round file for saw chain. I was thinking a wood rasp might be going to far, but maybe it doesn't matter? NSA used to offer a knurled .457 slug, but I don't see it anymore. Perhaps knurling doesn't affect efficiency, only fit/ease of chambering.

.251 and .252" slugs or any .25 cal pellet has a noticeable resistance when chambering in my Eagle Claw, but the knurled .250" slugs and NSA .250" slugs chamber with no resistance. I still have some NSA .457 slugs and .457" sizers and could test with my Challenger when I get a break in this weather.

I'll have to find the file and take a picture. It was just the first file I came across while searching for one that was flat on one side. It's probably close to my bar dressing file in texture.