I think the reason for the heavier barrel on the 590A1 vs. the 500 or 590 was primarily about supporting the bayonet in the event it was actually used on a human being. the 20" A1s have the lug if I remember,while the 590 non-A1s don't.
The way I understand it, the 590A1 has a heavy barrel for durability reasons. For instance, the barrel will not dent if banged into a ships bulkhead while passing through. They also added an aluminum trigger assy verses the regular 500 and regular 590's plastic trigger becaus eit was part of the military requirements. It's mearly a matter of preference. I own an 18.5" 590A1 and I love it. My brother has an 18.5" 500 and prefers his gun to mine. Handle them both and choose for yourself.
I have a 590A1 and you definitely need to feel it before you buy it. It is HEAVY.
that a big negative c-bag the non A1 still has a bayo lug (i own one) and the bayo doesnt hang from the barrel anyway it hangs from the worst concievable place on a shotgun... the magazine tube
which unfortunatly is the exact same one on both 20 inch 590s and will flex and brake if used alot
i personaly think the bayo lug was either an afterthought or just placed on because of military standards which really makes no sence seeing as how they have cut back bayo training to a minimum with non of it being done with shotguns anyway
the heavy barrel is on the A1 only to be durable enough to pass military testing thats honestly the only reason its on there is durability which is overkill seeing as how the original 500 barrel passed well enough to envoke a specialty model to be made (the 590 and soon to be 590A1)
yes true the lug itself does attatch to a barrel ring but the ring on the bayonet itself hangs from the magazine cap so in the end its... bothThat's not true, the bayonet lug is attached to the barrel assembly (the ring which slides over the barrel - not sure the name). After thinking about it I'm not sure I buy the bayonet explanation, it seems like the weak point would be where the barrel is soldered to that ring part.
Theres no heat shield because the barrel is too thick for the factory mossberg one to fit properly and they are too cheap to make a dedicated heat shield for one gunThe barrel was for sustained rate of fire (hence no heat shield)