I can see the Nitro Proof mark as above but anything else must be below the stock line. The screw to take it down is so narrow and shallow I need to cut a bit to take it out. It has been reblued at some time and this may have erased some marks. On the receiver I can make out a crown over N proof mark and to the right of that is St m g. I slugged the bore with a soft lead slug and it has a .326 groove diameter and .3085 land diameter, 4 lands and grooves.
I was lucky at an auction recently and scored 4 boxes of Western 8.56 M-S ammo, 200 gr. soft point. The last box I had split when I started shooting them so I stopped, pulled the bullets, punched the primer out, and annealed the cases. The splitting stopped. With the ammo I just bought I started by pulling the bullets and keeping the powder which looked fresh enough to shoot, punched the primers and annealed the cases. Luckily, all 4 boxes were the same lot number. I weighed each charge and got an average of 49.4 gr. of what looked like IMR 4350. I will re-assemble the rounds with a fresh primer and see how they do. I got all 4 boxes along with a 25 round box of shotgun shells and 3 5-round boxes of slugs, shipped for $56. I am tickled to have 80 original Lubaloy soft-nose bullets and new brass.
I have been shooting 170 gr. 8mm Silvertips I found loaded with 46.0 IMR4320 for 2370fps oal 2.965.
I do need to adjust the set trigger because all I have to do is touch it and it goes. Fun with a old rifle like this.