Gun is a ruger/marlin 45/70, less than 50 rounds down the pipe.

Brass is new starline.

Bullet is 400gr Speer FN

Powder load is 48-51 gr of N133

Primer is CCI 200 LRP



That line/gouge is deep enough that it catches my finger nail when I run it over it.

Brass issue or gun issue? I'm leaning gun since it's so uniform

I'd say gun as well. Have any other ammo to check see if it gouges them? I know you need an excuse to buy more ammo so you've been enabled.

I checked some hornady factory ammo I shot through it….same mark

Heavy reamer mark in the chamber?

Could be, I just know I don't like it and I don't want it beating up my Starline brass

I'd check with Gundoc see if it could be smoothed out. I've never run V133 I'd guess it's faster burning around Reloader 7 speed. I know the Speer manual likes that range for standard 4570.

For as much as the new 1895s cost, I'd contact ruger/marlin. Never had that issue w/ either my standard or SBL 1895 Marlins and run Starline brass for my loads.

I would get in touch with Ruger/Marlin BUT... they might giver you grief over the handloads so if you can get a couple of rounds of factory ammo the send/show to them, that hiccup would br eliminated.