Replacement shotgun barrels

[Futo Inu]

This is really a newbie question, but...I have a Rem 870 "Express Magnum" which accepts 3 and 1/2" shells. I received this in trade for service, so I didn't really make a conscious decision that I must have a "Magnum" shotgun. But can't argue with versatility. At any rate, my question is, when getting an aftermarket barrel - I'm thinking about both a rifled barrel and a short 18 incher - does the replacement barrel have to be designated as able to handle 3 and 1/2" magnum shells? Seems like the headspacing is irrelevant in shotguns, of course, BUT what about chamber pressure? Is it the case that the replacement barrel may itself be limited to 3" shells, but not the original barrel? Don't want to blow anything up in the event I try the magnum shells with the aftermarket barrel. Actually, I'm looking here at some shells I acquired somehow, and they say they're 3 and 1/4", which I've never heard of - I take it these only work in 3 and 1/2"-chambered shotguns? Thanks.

 

[ptpalpha]

Futo, the answer is that yes, if you plan on firing 3" shells the new barrel must be chambered to accept 3". The good news is that most of them are, because it simply makes sense when you enter the 870 aftermarket barrel business to make one chamber that will retrofit to every 870. I looked for one that was specifically 2 3/4" when I was building my slug gun, for the same headspace concern you'd mentioned. No luck. But the accuracy I get with the Hastings 3" is darn good with 2 3/4" sabots. Go figure.