Chamber lengthening (2 3/4" to 3")

[rbernie]

Any reason not to have the chambers lengthened from 2 3/4" to 3" on an 1970's vintage shotgun? I don't plan on shooting much 3" fodder, but I do have some sitting around and it'd be easiest to manage if all my shotguns had the capability to accept 3" shells......

 

[kingjoey]

You don't want to rechamber a gun/barrel for magnum shells when it wasn't designed for their pressure.

 

[rbernie]

I thought that the SAAMI pressure specs for 2 3/4" and 3" shells were the same, and only the 3 1/2" shells got a pressure boost.

No?

 

[ArmedBear]

What kind of shotgun, BTW?

 

[rcmodel]

Pressure isn't the problem. 2 3/4", 3" and & 3 1/2" Magnum loads all run very similiar pressures. So do field loads for that matter.

What you have to determine is if the action will feed 3" or not.

What kind of 1970's gun is it?
Pump, semi-auto, O&U, S/S, single-shot?
What?

rcmodel

 

[EShell]

Generally not a good idea. Even with the Rem 870, a very strong design, the factory warns against installing 3" ("Magnum") barrels on 2-3/4" ("Standard") receivers and shooting 3" shells.

 

[rcmodel]

It's not about strength.

It's about whether a 2 3/4" action will feed 3" shells.

In the case of the older 870, it probably won't.

rcmodel

 

[rbernie]

Sorry - I'm looking at possibly converting a couple of 1970's vintage Spanish SxSs. No feed issues - just chamber pressure and general 'is this smart' issues.

 

[Virginian]

Actually, the older 870s worked okay, then somewhere along the line Remington moved the ejector so the 2-3/4" receiver would have a problem ejecting 3" shells.
1100s the barrels and everything fit okay, but you need a magnum action bar sleeve to get it to function properly without drilling the gas port. Guess what they don't sell? You guessed it !

 

[rcmodel]

Spanish S/S's?
Should be O.K. unless they have chrome-lined bores.

That will make re-chambering them with a standard reamer next to impossible.

I can be done with the proper tooling, but then you won't have chrome-lined bores anymore.

rcmodel.

 

[rbernie]

Should be O.K. unless they have chrome-lined bores.

The bores don't have the 'overspray' of chrome on the muzzle end like my AR/AK chrome-lined barrels, so I presume that they're just standard chrome-moly or similar.

How else could I tell?

 

[rcmodel]

Dab of Cold Blue on a Q-tip or toothpick inside the chamber.

If it doesn't blue, it's chromed.

rcmodel

 

[PJR]

I'm looking at possibly converting a couple of 1970's vintage Spanish SxSs. No feed issues - just chamber pressure and general 'is this smart' issues.

I don't believe this is smart for a couple of reasons. These guns were proofed for 2-3/4" shells and opening up the chambers takes them out of proof. Being out of proof might not matter that much to you but make sure you are prepared to keep these guns forever. The first thing I look at when I'm considering a sxs is chamber length and it doesn't match the proofs then the consideration is over.

More importantly barrels on a sxs are typically thinner than a pump gun or semi and the barrels are often contoured and get narrower as they go forwrad. Cutting even a 1/4" further might, depending on the gun, create a thin spot in the barrels right at the point of maximum pressure.

 

[Sergeant Sabre]

I'm not a gunsmith, nor do I really know much about anything, but if it were my shotgun I wouldn't do it. I think you gain little with a 3" shell compared to the possible risks involved.

 

[rbernie]

I think you gain little with a 3" shell compared to the possible risks involved.

I'm not a 3" shell fan for the most part, but I do have some stock of 3" shells (slugs and 000 buck). My rationale for considering lengthening the chambers is out of a concern that somebody in/around my household may find themselves someday accidental dropping a 3" shell into a 2 3/4" chamber. If all of the shotguns that I own can digest a 3" shell, the issue is moot.

Is there some general rule of thumb WRT the shot pattern when firing a 2 3/4" shell in a 3" chamber? Is there more shot deformation because of the 'freebore' in the chamber?

 

[TrapperReady]

My rationale for considering lengthening the chambers is out of a concern that somebody in/around my household may find themselves someday accidental dropping a 3" shell into a 2 3/4" chamber. If all of the shotguns that I own can digest a 3" shell, the issue is moot.

Frankly, I think that's a bad rationale for messing with the chamber length. IMO, a Spanish SxS should not be a candidate for a diet of 000 buck and slugs. If your concern is safety, PJR is correct in stating that you'd be taking the guns out of proof and may well cause a condition every bit as dangerous as the one you are trying to prevent... except that condition would exist even when shooting appropriate ammo.

If you're concerned, put the 3" shells in a large box or 5-gal bucket and label it "Three-Inch shells - DON'T USE IN THE SIDE-BY-SIDES". That solution is nearly free, and doesn't create unintended consequences.

 

[PJR]

I wouldn't support that rationale either. Someone might put a 3" shell into a 2-3/4" gun versus you forever would alter the gun perhaps weakening it.

I'd rather shoot a 3" shell in a 2-3/4" gun versus shooting a 3" shell in a formerly 2-3/4" gun with the chambers reamed out, particularly if it were a sxs.