I have a .25 Bullberry in a 15" Contender, and recently came across 2x boxes of 6.5x52R S&B 117gr ammo. The 6.5x52R is simply the European designation for the .25-35, and I'm curious if they will safely fire in the .25 BB chamber. Both are .25 cals based on the .30-30 case, and from what I understand, the .25-35 has slightly more taper (and likely the shoulder set back a little). The round should headspace off the rim, so I am interested in seeing if the 6.5x52R will simply fireform to the .25 BB.

Thoughts?