The trigger guard has indeed been altered. I don't count that as being a big deal. Yeah, sure, it would be nice if they hadn't changed it, but in the grand scheme of things switching the trigger guard material is a non-issue. It's not like even the newer/cheaper ones break.

More of an issue would be MIM (metal injection molded, essentially the powdered metal you mentioned) used in some of the small parts. I'd have to look at my armorer's DVD to see what was changed and when. Since my class was armorer's level for PDs, the trigger/hammer assembly was basically treated as a unit. If something in it screws up, consider replacing the whole assembly, since it is easier and probably not a bad idea, since of one thing went Tango Uniform, the other small parts in the FCG may be worn as well. We went over working on the assemblies, but we didn't go into much detail about what was changed when.

Really, though, it is hard to screw up an 870. Even Remington can make them.

Mike

And then there is the difference between the police version and the civilian, bird hunter version.

The older one was virtually identical to the Wingmaster for finish and fit. The newer ones are still pretty good, of course.
Honestly, unless you are a stickler for finish, the old verses new thing is a wash.

I can see how a well used 870 may have a smoother release of the inertia slide lock. However, the slide lock releases in recoil so most shooters would never notice it even existed.
-----------------------------------------
From an earlier post:

Inertia slide lock?

If you hold the forearm tightly to the rear and dry-fire a Remington 870 or Mossberg 500, the action will remain locked. That is the forearm or slide handle must move forward slightly, as in recoil, to allow the action to unlock. This was to avoid an open action in the event of a hang-fire. This was part of the slide action genre going back to the Winchester 1893.

By the 1964 introduction of the 1200 Winchester (later 1300 and "Speed Pump"), primers had become so reliable that hangfires were virtually unheard of. Thus the slight delay in unlocking the rotary bolt of the 1200 was considered sufficient. So if you hold the forearm of a Model 1200/1300 tightly to the rear and dry-fire, the action will virtually fly open. Hence the term "Speed Pump." In essence it is a recoil assisted slide action.

I've heard about the pump-to-trigger pull time delay from several sources, but this is the first one I could find:

http://www.rem870.com/2012/04/27/full-interview-with-chris-costa/

"  Center gun into your chest  -  stretch...fire...collapse...cycle...stretch...fire...   "
   
Chris Costa uses some unusual terminology to describe mounting and operating a pump gun!