I’ve got an old standard weight Remington 1100 20 gauge that’s been in the family for awhile and I’m wanting to repurpose it, the serial number ends in X. And to my understanding it’s 20 gauge built on the 12 gauge frame. Right now it has got a smooth bore slug barrel on it and I’m wanting to use it for birds. I’ve been looking on the internet and have found some used barrels for it in varying chokes but some are 2 3/4” and others are 3”. The receiver doesn’t say anything about length of shells or if it’s a magnum. My question is can it shoot either, just dependent on the barrel? I’d like a 3” barrel to use on ducks..assuming the old steel will do fine with the new non toxic shot. Any help would be much appreciated.