I know they are all relatively similar because they are built to spec. Some companies will charge double what others do though, so I assume there are differences. My dream for this build is to have it compatible with .22 all the way up to the .458. 22 for cheap ammo, target practice, and becoming proficient with the gun. 458 because I'm the type of person who likes to be prepared for anything that may, but probably won't happen. Yes I'm new, so feel free to criticize. All input is welcome.