I know these aren't shotguns, but I own several AR-15's and an Armalite AR-10T (.308), all with aluminum alloy receivers and they are really strong. I've never heard of the military M-16 receivers cracking under harsh combat conditions.

I believe that the new aluminum alloy receivers are of quality material and will not let you down.

I believe the Remington 870 Wingmasters and the 11-87 model shotguns all have steel receivers, not aluminum alloys. Remingtons are great guns.