870 Left Hand Model Barrel Interchange

[Virginian]

Yes. But a 2-3/4" barrel on a 3" receiver is only good for 2-3/4" shells, and vice versa.

[Gamemaster32]

On a somewhat related note:

I recently acquired a factory-new 18.5" bead sight bbl for an early '80s 870P with 20" rifle sight bbl. The finish was different (not mil-spec parkerized) than the original, but I figured no problem, I can deal with a 2-tone shotgun.

The bbl went on fine and looked OK...until I attempted to operate the action. The bbl & synthetic forestock were binding inside, so I contacted Remington Law Enforcement Division to inquire. Their response was nothing short of they had never heard of such a problem. Their response/advice later progressed to that I should just sand the forend until it functions. Yeah...that would work; but I'm a perfectionist & like things to operate as designed.

As it turned out the bbl was in fact larger in diameter, & the forend, forend tube & bolt carrier (can't remember the exact nomenclature at the moment) had in fact been re-designed/changed.

Put the old bbl back on & sold the "new" bbl; not worth the expense & hassle just to have a bead versus rifle sights.

Have had the same problem with motorcycle parts, & although rare, no longer assume replacement parts will fit without an "issue."

[Virginian]

Okay, the magazine tube, and fore end tube assembly have not changed. The fore end nut retention system has changed, and barrel outside diameters have been several different sizes thru the years. The older guns were finished with tighter tolerances, so if you had/have a smaller diameter barrel you may need to sand down the wooden or synthetic portion of the fore end to clear the barrel. That is exactly what the factory did/does. If you get an old one, or a brand new one with a light contour barrel you will probably have to do some sanding to get an Express barrel to fit. The Express barrels are relatively fat. On the flip side I will bet money a Wingmaster barrel will fit on an Express with no issues.
But, the barrels will fit, and function, with proper "adjustments". An 'O' ring will solve the magazine cap retention system issue, or get a new cap. Or, don't put Express parts on a Wingmaster. The gun gods cringe at that.

[Gamemaster32]

The "forend tube assembly," bolt "slide assembly," & forends are different on the Police Model I have compared to a recently manufactured one; both which were disassembled & compared side-by-side.

The current example's bolt slide assy has a cutout area that corresponds to a tab on the action bar (which is an integral part of the forend tube assy). The parts don't mix-n-match. The forends are also different; the interior of the original 870 has a flat bottom. The newer one is concave. I never mentioned anything about the magazine tube.

Like I said, rather than perform unnecessary "gunsmithing," I left "well-enough" alone. I don't like making "adjustments," I like manufactures' replacement parts to fit the way they're supposed to.

[Virginian]

I stand corrected, I forgot about the "flex tab" modification. They did that so if you screw up and let a shell slip back under the bolt because you didn't push it far enough into the mag tube for the shell latches to catch it, it won't tie the gun up. I've never done it but I sure have seen it.
But the barrels will interchange.