Shotshell reloading problem

[Kola16]

I have a MEC 600 Jr. Mark shotshell reloader. I am still a novice reloader. I have all the parts for it to reload steel shot, and I have it set to 3 in.

So I had this problem last year, but I just thought it may be the Kent shells that I was reloading. I now have tried reloading Federals, and they do the same thing. The problem is that they won't cycle in my 870  They will go in, fire (with good patterns I might add), and then not come out. It is very hard to get them out 
Any suggestions 

[bobcat]

Does your 870 have a 3 inch chamber?

[Kola16]

Does your 870 have a 3 inch chamber?

Yes. It cycles factory loads fine. It is just when I try to reload those factory loads, they jam 

[Kola16]

And when I say jam, I mean that they are stuck in the chamber, and I can't pump the pump.

[Bigshooter]

Does the MEC 600 Jr have a resizer on it? 

[Bigshooter]

After doing a little reading on the MEC 600 Jr it does have a resizer on it, but it only resizes the brass and not the rim.  If its a resizing problem you will have to get a Mec Super Sizer which are about $100 for a new one and they resize the brass and the rim.  You should be able to pick up a used one for half that on ebay.  I'm not sure how you would find out if this is the problem but it sure sounds like the problem to me.  Maybe someone that has reloaded more shotgun shells than me will have an idea.

[Stilly bay]

it might be a combo of resizing and needing to polish your 870's chamber. its a really common problem with 870's, two years ago a friend had a brand new one that started hanging onto shells, we lightly polished the barrel with a power drill and some very fine sandpaper and it never happened again.

[Kola16]

I have read reviews from guys online with reloading problems. I am pretty sure that it is a resizing problem.

Although it i s a good idea to polish my chamber. How do you do that again 

[gadwall]

I probably loaded 50-60,000 rounds on a 600 jr before I bought a progressive mec.  I had the same problem years ago loading shells for trap.  The 600 jr resizes with friction and compression.  Make sure the resizing ring is all the way to the base of the shell at full stroke of the handle and the depriming tool is adjusted so the shell is cammed down and partly pops out of the tube when you bring the handle back up.  Try replacing the resizing ring (the bottom one on the tube) and see if that helps.  Mine was wore out and this solved the problem for me.

Gadwall