I'm sure it will go bang. I THINK, since the action sleeve is heavier on a mag gun, it might not cycle the second shell as intended. Just a WAG Good luck
putting 2 3/4" bbl on a mag gun is not a safe practice, since the 2 3/4" may be mistaken for a mag and if you chamber a 3" in it....well. theres also an issue with the bolt having to travel father back than the 2 3/4" bbl extension/ejector will allow. swip swapping 1100 bbls is a slippery slope with all the design changes its gone thru.
Just curious, if a 3” shell WILL fit into and fire out of a 2-3/4 chamber wouldn’t EVERY 2-3/4 gun be dangerous in that someone could “accidentally” put a 3” shell in it?
itll fire, but the 3" crimp will expand beyond the forcing cone, not sealed in it. thats the danger. reason a mag can handle a 2 3/4" hull is because it expands before the forcing cone and the extra long bolt that has an extra long bbl extension will eject it as it travels all the way back. if you change bbls, the ejector is advanced and forward of its proper position. and of course, if someone looks down at the gun and says...hmmm its a mag, and puts one in.....thats the known and documented issue that has been gong on since the 1100 mag was invented. not everyone looks at the bbl markings. im sure a gunsmith can chime in and give a good scientific explanation better than me.
The OP wasn't asking if he can fire a 3" shell out of a 2-3/4 chamber. We all know what happens. The question was if a 2-3/4 barrel will fit on a 3" mag receiver. I assumed, yeah I know what it means, that he was going to use 2-3/4 shells in the gun so, yeah, it will work.
I have 2 magnums the I shoot trap and sporting with that have non magnum barrels. They function perfectly. One has a factory Remington barrel and the other has a hastongs barrel. I even have a 2 3/4 barrel on my police magnum 870 for when l loan it out for trap
I have a magnum gun and I also have a Skeet barrel. I have shot more from the Skeet barrel than I have from the Magnum barrel. The receiver will work fine with the Skeet Barrel. No worries. Just don't shoot 3" out of the Skeet Barrel, it won't cycle well.