The main 'caliber' restrictions in tactical matches that I've been hearing the last year or two is a) no magnums and b) a velocity limit of something like 3100fps, even for the 6 / 6.5mm stuff, both mainly oriented towards limiting the damage done to steel targets (even the AR500 stuff). They ain't cheap, and someone has to pay for new ones - usually *not* the shooters. A few places have '.308 only' matches... to try and stick to the practical/tactical 'real-world' emphasis, not the 'gaming' that is so prevalent with people choosing flat shooting high-speed low-drag calibers so they can beat the .308s. I'm finally rebarreling my #1 tactical/practical stick because I'm tired of playing second fiddle to the high-speed low drag crowd. I don't mind losing, but I want it to be on a level playing field so I know it's just me.
Now that we've gone sufficiently far afield from the topic... back to your regularly scheduled programming