As a follow up to 2xtaps Remington 870 Armorer questions.  

A few of us mentioned remington plastic followers seizing in the magazines.

Let's discuss as I just experienced shotgun #2 this last Wed. during semiannual qualifications

SoS

I've had two followers fail me.

#1 was about 5 years ago in a personally owned firearm.  It's been long enough now that I can't recall if it was my 870 special purpose or my 11-87 special purpose.  The failure was the grey/silver plastic magazine follower seized in the tube preventing the loading of the magazine.  This occurred with zero rounds in the gun.  The follower wedged right at the opening and I had a very hard time pushing it back up.  Solution was getting a replacement at a local shop that was a Remington certified smith.  No failures after replacement.  Joe the gunsmith said it's not all that uncommon, he's seen more than a dozen.

#2 was this last week at qualifications.  I had a new department issue 870 Police synthetic shotgun.  It had been test fired by department armorers prior to issuing.  I also fired about 30 shells through the gun prior to carrying in the patrol car.  I had also just used it the week before to put down an injured deer in the water and had no problems with the magazine.  Last wednesday we grounded our guns on the fifty yard line prior to shooting for refressher instruction.  Then we loaded (i merely attempted) to shoot our course of fire.  My (orange) follower seized in the gun.  I could not for the life of me push that follower up with my thumb.  The follower had expanded in the heat and seized right at the magazine tube opening.  An instructor disassembled my 870 on the line and popped it free with a leatherman while the whole line waited.  

(In my haste to get ready I stupidly misloaded my gun with buck from my ready pocket instead of slugs and fired 3 of em before noticing, and fired the next two anyhow, (surprisingly 38 out of 45 pellets hit scored areas of a NYSP B-27 from 50(2 rds), 40 yards (1 rd), 35 yards (2 rds))

SoS

Almost all of out 870P's are 20" models with the factory +3 extension.  All the followers are black plastic Remington versions.  None have failed to my knowledge.  The guns are in/around 15+ years old and in-car temperatures range from well-below freezing to "oven-hot" in the summer.