I've got 3 Mossberg 930's; 1 - 930SPX & 2 - Walnut stocked models, I've shot over 20,000 rounds between the three guns over the last 3 or so years.
The only two problems I've hade were, one time I didn't put the bolt handle all the way back in after cleaning and sometime during the next round of shooting it went missing, didn't affect the gun at all but I lost the bolt handle. I contacted Mossberg to buy another, they sent me two for free....
The second issue I had was, I swapped barrels and went shooting only to find that forgot to swap the pistons, so the gun became a single shot....
SO, other than two operator induced malfunctions I have never had a single failure.
I shoot Remingtom 7/8 oz Game & Target loagds or hand loads that are similar and don't have a problem....