The Mossy pump has been used by our military for 25+ years. Reports of Mossy,s having fired 50,000 rounds in training without any gun malfunctions are pretty good evidence they keep on chunking.
Police dept´s use Mossy´s and I see nothing in print that says they have a unacceptable failure rate. I have several 25 year old ex-police model 500´s and they function without flaw. I have one here in Peru and I am staking our home proctection on it without any concern of firearm failure. It has consumed some rather high pressure round ball loads without any problems.
Mike in Peru