question regarding 870 express mag

[UltimaSE]

I just purchase an used 870 remington express mag. I'm now currently looking for a shorter barrel as this 870 came with a 29 inch barrel. The barrel the 870 came with says "use 2.75 or 3 inch shells in mag recievers, use only 2.75 in all others." Now my question is I found a barrel that is marked 2.75 inch shells. So I would think that with that barrel I would not be able to shot 3 inch shells through this shotgun any more. I'm not sure if I am correct in assuming this.

Since I was curious how much the barrel affects the chamber I took the 870 out to take a look. When I look at the reciever it seems like the barrel does not impact the the size of the shell in the reciever. So I'm wondering if I were to purchase this barrel would I still be able to use 3 inch shells since this is a mag reciever or would the barrel make it so that I couldn't use 3 inch shells?

Thanks in advance,
UltimaSE

 

[Dave McC]

Use 3" or shorter shells in a bbl and receiver so marked. Shooting 3" shells in a 2 3/4" chamber may cause this 870 to emulate a grenade, or to develop headspace probs much, much sooner than it would otherwise.

Were you planning on using the short bbl for H/D?
If so, you're under no serious constraint limiting yourself to 2 3/4" shells.

 

[UltimaSE]

I figured as much, is the same problem true for using a barrel marked 3 inch and using 2.75 shells?

UltimaSE

 

[Dave McC]

You can use shorter but not longer ones. A 3 1/2" chambered 12 ga will take all common 12 ga ammo, down to the old Brit 2" dwarf loads.

 

[Al Thompson]

Ultima, you can go down bit not up. 2 3/4 in a 3 inch chamber is fine, 3 inch shell in a 2 3/4 chamber raises pressues excessive amounts. The 3 inch will chamber, but when fired the mouth of the 3 inch case protrudes into the barrel and constricts the shot, hence increaseing chamber pressures dramaticly.

Other than (perhaps) waterfowl, no need for the 3 inch round.

Giz