You think the weapon is really that big? It big enough to carry and doesn't seem that much of a burden to whoever is carrying it. I'm thinking maybe a Claymore or something similar. Michael, Angel and Saul got excited about Burt pulling one out when they were going back to the tower, why wouldn't the Mallers? Not saying that is the weapon but it could be something like it that can do some damage if need be.

But IF I were willing to bet, it's more than likely not. If the weapon is from Burt's safe hell it could be almost anything, maybe even a grenade launcher of some sort. Reason for saving it is limited ammo and last resort. Who knows but Kc?