Corrosive primer military ammo, barrel left not cleaned with water based solvent, will eat away lands very quickly.
Have you tried SARCO? They have a lot of mil-surp not advertised, but are glad to check their inventory for you, if you just call them.
If you have some of lands still left you might try cast lead bullets at lower velocity (and pressure) since rough bores present more drag on bullet.
Also, if you have a C&R ffl03, you might get a U Fix Um from Century. I heard they bought all the Samco inventory, so some 91s may show up soon on their site.
If rest of rifle is nice, consider what nice ones sell for today, not what you gave for it.
Once I bought some MN 91/30s U Fix Ums from Century. They hadn't been fired since REFURB (sorry Windows cell keeps changing to "return"just before I submit) and not a thing wrong. $25 each!
Those 91s 7.65 are great little rifles. I'd keep it stock,fix it right and enjoy.
Pat