[357phase]

I have an 870 police that came with factory extension.If I remove the extension,what magazine spring retainer would I need?I know I'll need a magazine cap.May do the same with my express so would the same spring retainer work for both?Express also came with factory extension.I know I'll need the shorter springs.Magazine will hold four shells when I'm done remodeling.Thanks for advice.

[dfariswheel]

You'll need the OLD STYLE split spring steel "Cup-washer" magazine spring retainer AND and an old style magazine cap with the dimples around the outer perimeter.

These are available from Brownell's, Gun Parts, Midway, and many others.
Your local gun shop just might have some laying around as take-offs.

http://www.brownells.com/aspx/ns/schematics/schemmfg.aspx?schemid=134&m=12&mn=Remington%c2%ae&model=870+Standard+Weight-+12%2c+16%2c+20+
Items number 33 and 38.

Note that the old style magazine cap IS different than the New Style cap used on the Express models.
The Express model caps had "teeth" raised in the center inside of the cap.
The Old Style caps have the machined "dimples" around the outer side of the flange.

[357phase]

Thanks.I believe that is exactly what I needed to know.Will the old style cap with dimples work on the express that came with the factory extension?