The 25M is a .22 Mag. Marlin did make a 25N and, of course, the 25, both of which are .22LR's. There have been a few mag design changes over the years, so you will have identify which version yours takes. The more popular mags are available at Wal Mart, Gander, Bass Pro, and most gun shops.
I have a few Mod 25's including both the Mag and .22 Lr. In short, they are fine rifles. Very hard to top in their price range and will give a good account at the range side by side with more expensive rifles. The newer 925's have the 900 series trigger which is an improvement over the older style. I have a hard time passing them by when in the in the $100 - below range. I can't say enough just how solid a rifle and value they are. I think Wal Mart sells the Mod 25 .22 LR for less the $140 new. That's still a deal in todays market.
I reguarly see Mod 25's at gun shows and shops in real good condition for $90 - $120. Well used versions in the $70 range. They make great re-furb projects and lend themselves to easy accurizing modifications. An example is the re-furbed the rifle below I recently completed. It was bedded with Acra Glass, floated, re-blued, re-finished and the trigger lightend. The scope is a Tasco Golden Antler 3X9X40. I've not had a chance to shoot it since the re-furb.
Before:
After
One more thing. The current Gun Trader shows that a Mod 25 in exellent condition has a current value of $145; in good condition, $93. Fortunately, the local market has not caught up with the book value.
