I picked up a used 870 Wingmaster Police gun and it looks great. One problem, the rounds do not chamber well. I believe the part that lifts the shell from the mag. tube into the chamber is the carrier? This seems to not be working well. What can I do? Is there a weak spring associated with this part or is there another problem I should look at? Thanks for any help.

I suggest starting with the cheapest thing first and work your way up. . .Probably it's the magazine spring. Here's a link to Wolf springs for your 870

www.gunsprings.com/1ndex.html

Quoted: How is it not working well? Is the shell not coming out of the magazine fast enough? Is the carrier not lifting the shell correctly to feed?

The carrier is not lifting the shell completely enought to feed in to the chamber.

Sounds like you need a new lifter spring.  Check Brownells, they are a lot easier to deal with and cheaper than Remington.

Before buying any parts, try giving the trigger group a good cleaning.
Most people never clean a shotgun, especially the trigger group, and they're typically gummed up with plastic shotshell residue, burned powder particles, shavings of case heads, and dry of lube.

To clean, get a spray can of CLP Breakfree or Rem-Oil at most gun shops or Wal-mart.

Remove the group from the gun and give it a GOOD spray until it's dripping wet.

Allow to soak for 30 minutes standing up so it will drain.  Shake and wipe off the excess lube, and work the shell lifter up and down a few time to check for free movement.

If this doesn't do the trick, THEN you can install a new lifter spring.