I have an older 1974 Remington 870 Express. I have the original 28 In Vent Rib Barrel and a newer production (2000’s) 18.5 In bead front sight barrel. I have also put on a +2 Choate extension. With the original 1974 barrel on the gun, everything runs fine. When I put the shorter barrel on, the action becomes extremely stiff at the rearmost position of the stroke (when I pull all the way back on the pump handle). The action practically locks up at this point.

When I tinker with the magazine extension by backing it off a few clicks, the problem seems to lessen a bit but it introduces some wobble into the magazine extension.

What could be causing this?
Is this a headspace issue?

Thanks for the help.

Buy a Remington mag extension, cheap aftermarket parts are cheap.

From your description, the only thing I can suggest looking at is where the notch on the new barrel engages the ejector slot in the receiver. Compare that relationship with the original barrel.

Will do. Thanks

Good suggestion. I’ll see if the problem persists with the original cap.

Also check the fore end to barrel fit. I once put on and after market fore end, went from factory wood to Choate synthetic. It was just enough to snug up the action at the end of the throw. A little file work cleaned it up. It was also with a different barrel.  The profile on the 18.5" might be just a tad thicker.

I also believe that the foreend may be contacting the bottom of the the new barrel. I had to relieve my foreend.

Just tried this and it worked. Thanks everyone