CB unrelated shotgun question

[GrayTech]

For a quick test, try pushing the primer partway out of a non-fired shell and then chamber it. This will give you a rough idea of the head space. If you insert a tube or rod into the shell, you can measure the combined length with a caliber and then do the same with the primer fully seated.
The difference will indicate the head space.

Now that is pure genius!!!
Going to try that right now...

[Hogtamer]

Assuming these are new factory shells? It's not common but possible that shells are loaded wrong at factory. Those are serious overpressure signs. And in that last pic, what are those consistent scratches on the brass? Also on the 870, not only make sure the cap is tight but there is a recess at the top of the forearm in which a nut holds the forearm on the slide action. It has 2 indentions that you need a special tool or a thin screwdriver to tighten. it is very fine thread on the thin tube, not always perfectly machined on the newer guns, and sometimes requires a little "wiggle" on the forearm to tighten completely. I've got 6 - 870s and have shot some monster slug loads out of them, only 1 of the newer models though.

[GrayTech]

Assuming these are new factory shells? It's not common but possible that shells are loaded wrong at factory. Those are serious overpressure signs. And in that last pic, what are those consistent scratches on the brass? Also on the 870, not only make sure the cap is tight but there is a recess at the top of the forearm in which a nut holds the forearm on the slide action. It has 2 indentions that you need a special tool or a thin screwdriver to tighten. it is very fine thread on the thin tube, not always perfectly machined on the newer guns, and sometimes requires a little "wiggle" on the forearm to tighten completely. I've got 6 - 870s and have shot some monster slug loads out of them, only 1 of the newer models though.

All factory loads. Those pictured are high velocity steel shot. Didn't notice any crazy recoil, and primers are not flattened, so I doubt its over pressure.
Didn't notice those scratches before, will take another look, bolt face is smooth so not sure what could cause that.

Only tried the vented rib barrel so far, until I noticed the deformation. I wasn't about to try shoot slugs if there was a problem. That barrel has been replaced so I will test again with that as soon as I get a chance.

I will take a look at the adjustment you pointed out. Thanks

[Texas by God]

I have had two 870 Exress ( a12&a16ga) that acted similar. On both there was a burr on the locking abutment on the barrel. A bit of careful Dremel work solved it. As Runfiverun said- they are not Wingmasters. Kind of like the Rossi lever actions- some work fine out of the box- and some don't. I hope you get it worked out. Best, Thomas.

[GrayTech]

Replacement barrel seems to have solved the jamming issue. Hoping it's good now, will test fire as soon as I get a chance.