Proofhouse load and regultion load the same? I have never heard of such a thing, and can't imagine its being done anywhere in the world in any proofhouse. After all, the purpose of proof, is to determine if gun/rifle will withstand breech pressure substantially above service (regulation) load, the load intended to be used normally. If it does pass that test, it is assumed to be safe for firing the service load. Now, if one were to think that proof load is to be same as service load, that means that with every normal daily firing, a high pressure proof load is safe to be fired, nonsense. Just because a lighter weight bullet may be used for proof, than proposed service load, means nothing; what mean something, is what breech pressure the proof load subjected the action/barrels to, regardless of bullet weight, compared to proposed service load breech pressure, regardless of bullet weight.