870 express magnum action will not lockup

[macgyver]

Put together a gun from parts all over, most parts used.

When I operate the action the bolt will not lock up. If I undo the mag cap 1/8 of a turn, maybe less, it will lock up just fine i have no clue where the issue may be. I saw the other post about maybe being the extractor, to me it looks like it setting up where it should.

Any advise what to look at or test to see where its hanging up would be appreciated.

Jason

[ChillyB]

Is this your only 870? I'd try a different trigger assembly. Split the deck on potential issues.

[ChillyB]

And are your action bars straight?

[macgyver]

HI guys

Thanks for the reply

It is my only 870 unfortunately, I wish I had another barrel to try it.

The action bars look parallel. there are a couple of notches in them where they catch up on the shell latch spring on either side. It looks ok to me if you would like me to post pics I can do that as well

Jason

[ChillyB]

Recommend studying interweb for detailed explanations of how an 870 works, what each part does. Bet you can figure it out, and I'll also bet it's something simple. Most important part right now is understanding how the bolt locks to the barrel, and what keeps the slide locked forward.

[Scorpion8]

The action bars look parallel. there are a couple of notches in them where they catch up on the shell latch spring on either side. It looks ok to me if you would like me to post pics I can do that as well

Since it happens on the "last oompf" of turning the magazine cap tightly, try holding the barrel straight into the receiver and not using the magazine cap to push the barrel into place as you tighten it. Make sure the barrel is straight, and not binding the action bars and then tighten the magazine cap down. You don't need to super-torque the magazine cap.

[macgyver]

so after a lot more digging into this issue, here is the latest

I picked up another barrel, ( used one with a good breach) Fitted it to the gun and the same exact issue. will not lockup unless you release the tension on the mag cap.

on further investigation, I have noticed something, the slide release is not coming all the way out unless you release that tension on the mag cap.

The trigger group I bought is supposed to be out of a magnum 870, My question is, is it possible this is a "small frame" trigger group.

I have measured my receiver and have verified it's a large frame. is there a way to tell if the trigger group is from a small frame 870 or a large frame? is there a mark or an imprint on it to be able to verify?

it appears as though the action bar lock has some shiny spots on the leading edge, it feels a little sharp, it looks like wear I guess but cannot confirm its "normal"

Another thing I've noticed on this trigger group is in the middle of the trigger group there is a spring that loads the Action bar lock. this spring extends approx 3-4mm above the action bar lock. this looks a little high to me but wondering if someone can tell me if I may be going down the wrong road on this one.

At least more information or insight would be helpful
thanks in advance
Jason