So I picked up the 870 today to do some side saddle reloads and discovered a problem with the gun not feeding. I chambered a round from the magazine and ejected, then nothing came out of the magazine. Long story short, either the follower, spring, or she'll rims we're catching in the joint. I was actually getting hangs feeding and reloading so I decided to round the joint. After I finished I cycled about 30 rounds through it and it seems to be running smooth now.

Thankfully I did this today as this is my HD gun. This could have been a bad situation if I actually needed to use it. To clarify any concern, safety was priority when when unloading the live magazine.

Thanks for the info. Do you know the manufactured date of your 870? This could possible help others out there that might have a similar problem.

I don't know the date but it's a late model. It has the ball detent barrel. The edges are probably on all models. They were sharp edges on both the mag and extension.

Is this a Remington or aftermarket extension?

You didn't mention if you were using factory or reloaded ammo, but one thing I found, which may or may not be contributing to your problem. If you are shooting reloaded shells, the rims often tend to expand due to resizing. I have had the issue of rounds not coming out of the magazine tube in several different shotguns, extension and regular tubes. I did the same things as you, radiusing and deburring the magazine tube, but to no avail. A collet sizer, such as a MEC will cure this problem.