[Badger Arms]

I know that several gunsmiths do this work, but what is involved in it and how hard would it be to do it at home? I've got a 3" Magnum barrel already, so recutting the chamber isn't an issue.

[dfariswheel]

Other than the barrel, the big change is a longer, 3"-type ejector assembly.

The old 2 3/4" ejector has to be removed and a new 3" ejector needs to be riveted in place. This can be done at home IF, you have the special tools needed for the special Remington rivets.

If you don't have the tools, don't even think about trying it yourself.

The special rivet tools can be bought from Brownell's, but it'll likely be cheaper to get a gunsmith to do it for you.
It's not a big job, it's just that it's one that can't be done properly without the tooling.

[P95Carry]

I quite forget the relative ''proof'' pressures but ... surely an increase in chamber capacity - in itself - is not so safe if ''burst'' strength is only proven for the 2 3/4. The three inch shells have way more pressure.

Better surely to have barrel designed and proofed for 3"?

[Badger Arms]

Yes. Actually, there is no difference in receiver strength and 870 barrels have always been able to handle 3" pressures.

[Edward429451]

The ejection port would have to be lengthened also is my understanding. Probably not cost effective vs an 870 express NIB.

Whatcha' gonna do with a 3" that a 2-3/4" wont do? (Not being sarcastic or anything, genuinely curious.)

[Badger Arms]

Mostly just a curiosity although I might try to do it. In Alaska, the extra 2 or 3 pellets of buckshot might make the difference between making it home for dinner and becoming dinner.