I have a Saint Victor - .308. I just bought a Wilson Combat 20" Super Sniper and was able to install it. You can replace the stock barrel with any barrel that fits the DPMS pattern.
The hardest part I encountered was removing the gas block pin on the stock barrel so I could use the stock Barrel Nut. I actually ordered another handguard and barrel nut because the pin was so tough to get out. I ended up drilling it out, but was able to get it removed - the gas block got destroyed in the process. oops.
I will admit that I have not shot this yet, but I will shortly.
