A lot of gun manufacturers only batch-test their guns. They'll take one example out of a batch and test-fire it, and if it's okay the rest are considered good to go as well. And often it's just with normal ammo, not proof loads. Colt is one of the few who actually test and proof-fire EVERY gun they make. It's just one more hidden detail that contributes to the higher price tag on a Colt compared to equivalent manufacturers.