bull1870,

As a full blown hand cannon nut (Contenders and Encores here) I would go with the 308 if you don’t reload. The 308 can be found at every gun shop in the country with a very good selection of loads. The 7mm08 is a fine round and would be my first choice for a reloader as you can really tailor it for the shorter handgun barrels. I love the .243 and have taken a bunch of deer with it but out of a handgun I think it's a little light.

Before you plop down your hard earned cash on a Striker I would take one more long hard look at the Contender. There is a very good reason they are the #1 single shot in the world.