Travis
You may have seen these Lilja barrels but if not I'll post a link. I don't own a 455, mine are 452's and 453's, but these barrels have been getting very good reviews at rimfirecentral. I've heard of fifty yard five shot .2's being common in 22 LR with good ammo. Not real sure on the other calibers since I'm a 22 shooter mostly.
Be advised, a match chamber will likely not extract an unfired round.
http://www.riflebarrels.com/products/cz_455.htm
