BudsGunShop.com - 3" only?

3" or less will be fine, just not longer that 3.

Hi Bruce, this has a 3" chamber, so it will fire both 2.75" and 3" shells.
Stay safe & have a great day!

it will cycle most 2 3/4 inch shells it may not cycle with "light" target loads

It's chambered for 3" so it will absolutely shoot the smaller 2-3/4" shells. I looked and could not find a tube extension for this model.

Hi Bruce and welcome. It will run both 3 inch and 2 3/4 shells no issue. A plus 2 extension is available here for 7 + 1 Capacity : https://battlehawkarmory.com/product/mac-80041050-m4-extension-12ga-2-1014

Yes.