J. Stevens Tip up rifle of unknown caliber

Hi all, I have my grandfathers turn of the century J. Stevens tip up rifle and I thought for sure it was chambered in .32 Short Rimfire, but I finally slugged the chamber and bore and both are coming in at 0.275”. I am wondering what this could possibly be? It is definitely rimfire, and is is marked “32” with “short” under it. It does not appear that the barrel has been lined. Any ideas? I will post pictures later. Thanks

Well no pics yet and no replies. I rechecked my measurements and the chamber is .276” or so and the bore more like .265 or maybe smaller but this was measured just at the very end of the bore so it’s likely it has opened up over the years. Convinced this is .25 caliber Stevens Short rim fire which has a .276” diameter case and a .251” diameter bullet. I was expecting it to use a heeled bullet like the other rim fires, but no. Ammo very hard to get. I think I will get some .25 acp which has the same dimensions for most things and recharge with black powder and either modify the rifle to centerfire or most likely bore out the back of the cartridge to use a .22 blank or emptied case to set off the black powder using the existing rim fire pin which should still hit. Only worry is that the smaller rim on the .25 acp won’t be big enough to properly chamber or extract the round.

Thoughts?

Thank you both for your replies, yes castbullets has some good threads that touch on this and it sounds like the .27 caliber powder blanks fit the chamber well since the .25 Stevens cartridge has a .27 chamber and an internal bullet, unlike the other rim fires which use a heeled bullet of the same diameter as the case. So, that is an option. Another is to buy some actual .25 Stevens short ammo (you can find a box on gunbroker for around $90 last time I checked). And then just use those, bore out and countersink the back after firing to accept a .22 rim fire case and reload same as I had proposed with the .25 acp. I may go that route as what bcrider stated may be the case, I.e. the bore is trash. In which case I might not even get through a box of ammo before shelving it or choosing to reline etc. I think I’ll spend the $100 or so to get a box of actual .25 Stevens short and worst case I took a few shots and spent some money, and best case I have brass that I can do something with to keep her running.

As a side q, what are the thoughts with jacketed ammo and old presumably soft barrels? If I did go down the .25 acp route, they would have the jacketed bullets.