Congrats on the Valmet, for the caliber you have makes it a particularly useful cartridge for most of the hunting one might do in the "lower 48". As has been said, "break actions" of this design are not normally designed to "hold" the pressures of "bolt" guns (the single shot Merkels and Krieghoff being a couple of exceptions). I found 7X57R data in Norma's (new) reloading manual, but unfortunately it only gives loads for their powder. Looking at their 7X57R, compared to their regular 7X57 (bolt) loads, their Max loads only look to be 1 to 2 grains less with "like" bullets. On the section on 7X65R, which is also used with break action guns, they state that because of the weaker actions they hold the pressures to 55,100 PSI or less. The Valmet I have owned had an extra set of 30/06 barrels, and I worked up loads that were at least 2 to 4 grains under Max. I had more trouble finding a load that would "print to the sights" than finding a load the Valmet would digest. I would not (and did not) load this type of action like an Encore, or one of the more expensive Jager rifles. The Valmet is a fairly strong action, as far as shotgun designs go (sliding top breech and all), but they will shoot loose with volume firing "abuse" (just pick up and open one that has been used for trap or skeet over a long period!). You've got a nice, versatile gun (if it's been taken care of); cases may be a little hard to find, but I'm sure S&B, RWS, and Norma may be of help. Good luck!
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