I picked a few of these out of a junk box at a local gun show a while back. Don
Looks like a “reload” tracer to me. The projectile length and ogive shape is wrong for the 7.62x54r as is the second cannelure. The red tip color would be correct for an “Observation” or “Explosive” Incendiary, but in this case I beleive it to be a tracer projectile from a 7.62x51mm cartridge.
It looks like you are correct. I looked at the others in the sack and some show signs of being reloaded. All the bullets measure out at .307.