Question makes no sense. A Mossberg 500 pump-action shotgun has nothing to do with muzzleloading firearms which were originally made before 1850.
Question actually makes PERFECT sense to anyone who is knowledgeable about the Mossberg 500, and it's ability to suit nearly any hunting purpose simply by swapping out the barrel (takes under 10 seconds; nice try OP). The manual for the 500 Muzzleloader, which can be found on Mossberg.com, under the Customer Service tab,
recommends either a 385 grain bullet with 90 grains of Pyrodex or a 410 grain bullet with 80. The manual, unfortunately, does not clearly state a maximum safe load. There is additional info in the manual for regular black powder and ball rounds.
100-325 or so
Yes. It is a 20 ga. youth pump action shotgun.
Yes, the 600 At is the same model as the 500 series, but with a different designation for sale in New haven stores. So yes, all Mossberg 500 after market or OEM parts will fit it.
No
You will have to contact Mossberg
Mossberg, Savage, Remington, Winchester, Marlin, .22 caliber rifles. They could be lever action, bolt action, pump, or semi auto.
1955-1959.
Not likely. The 930 is a gas operated semi-automtic. The 500 is a pump.
The most likely causes are not operating the slide action hard and fast enough (pump) or not holding the gun securely against the shoulder (auto).
50-160 USD
Mossberg
Mossberg. It was sold through Montgomery wards. Its a Mossberg 500 with the western field name. All Mossberg parts interchange.