The range at Fort McMurray does silhouettes once a month, very informal but some disgustingly good shooters (I'm not one of them....).
You need a 308 as a minimum in order to knock the metals over...I can hit them at 200-300M all day with a 223 and all I get is a "ping" and a bit of movement. You want something in a heavy barrel, most common choice is a Rem 700, either in SPS or 5R.
I've got a 5R and know folks with SPS, biggest difference between the 2 is SS action and barrel plus the nice stock on the 5R vs. the basic Rem 700 and black action/bbl on the SPS. I went 5R for the SS look, particularly since I plan to use the action for a custom build once I shoot out the barrel. Really a personal choice between the 2.
As soon as you get your rifle start re-loading! My 223 & 308 shoot crap with bulk ammo...it's amazing what loading your own can do. I'm just getting into it but have used some friends hand loads and what a difference.