.25-35 in .25 Bullberry?

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?

I did some research when I was considering which 25 caliber barrel to get and found that, based on case dimensions, it should work just fine. I would trust a Bullberry chamber to be tight enough to avoid any split brass during fire forming. I've had MGM chambers in X-30-30 chamberings that were not cut to the same tight tolerances. Amazing that you found that ammo!! :)

Maybe I am missing something here but 6.5 is .264 and 25 is .257 considerable bit of a difference here, Un less the metric system has changed ?

Put a caliper on the bullet make sure it’s .257

Quote:

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Put a caliber on the bullet make sure it’s .257

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No reason to. The 6.5x52R is one of those odd Euro equivalents, but the bullet is definitely .25 caliber.

Here are a few pics:

https://i.imgur.com/qv54KB3.jpg

...and here are a few pics compared with a resized .25 Bullberry cartridge. Oddly enough, I wasn't able to locate my fireformed .25 BB cases to compare. You can see that the 6.5x52R (.25-35) has considerably more taper, and easily drops in/chambers in the Bullberry barrel.

https://i.imgur.com/CXBBBXW.jpg
https://i.imgur.com/dZqKZZi.jpg

Here's the actual Contender....

https://i.imgur.com/efyOjtN.jpg
https://i.imgur.com/WvMpAMU.jpg
https://i.imgur.com/axzqreo.jpg

Now, I did do a little measuring to compare the two cases. The x52R measures 0.490" at the rim, factory resized Win .30-30 brass was 0.500". Base of the cartridge, just above the rim, was 0.411" for the 52R and 0.4165" for the Win .30-30 (this is all 1x fired brass). OAL for the brass is 2.040" on the 52R, and 2.042 for the Winchester. Outside neck diameter is 0.2805 in the 52R, and 0.279 on the resized .25 BB. Just below the shoulder, the 52R tapers to 0.365" and 0.400" for the resized .25 BB cartridge.

I had a 25BB and some 25/35 brass and tried to fire form the 25/35 in the 25BB and about 1/2 of the brass slit along the body shoulder junction. If I had used the COW method they may have formed, but I did not try it.