I have owned or own almost all of the combat shotguns.
The 1301 is the lightest and really soft shooting and cycles really fast. Fairly inexpensive compared to the benlli M4. With the safety in front of the trigger its easily converted/reversed to left hand and it pretty nice.
The M4 is heavy and seems to kick more than the berretta but does cycle fast and they are really tough. all kinds of youtube videos to proves. (1301 does too)
The mossberg 940 shoots good is inexpensive compared to the others. I am also left handed and I do like the tang safety. It shoots fast with light recoil but has a "weird" recoil impulse that is the only hickup. With the new 940 "pro" coming out it might be a really good option. The tang safety is really good for lefties.
My favorites are my Remington Versamax tactical. They are a benelli M4 type clone. they are heavy for walking around quail hunting but they are the fastest shooting and softest shooters in my opinion. Remington has support issues right now but all of the M4 benelli parts from brownells work great.
I haven't shot the A300 yet but If the safety is in a spot you feel like you could train into I think you would be really happy with the A300 or the Mossberg. They are both american made
