Firing pin question

[BBBQ 0]

I bought a spare firing pin several months ago. This week I had my JSAR apart, so I compared the pin I have (top) with the pin I bought (bottom). I noticed two things, 

For the area circled in blue, that circular piece has some wiggle to it and the spot weld holding it fixed the to the pin body is broken.

For the area circled in red, this smaller diameter area is clearly longer than what I have.

Did I get screwed? Is this firing pin any good?

[ArtR 0]

From information that I have gleaned, the firing pin ring was pressed into position, and  'weld or braze' in place. As long as snug in the 'groove', it should probably work okay. The distance between the area in red was  0.687"  but was increased to to 0.703"in one of the latest revisions. Whether they were trying to change weight/mass into the FP assy, is anyone's guess, but that would be my thinking.

[tsmgguy 0]

Are both pins serial numbered? The spare pin/collar/spring assembly in my collection is numbered H2039 and is most like the lower in your photo. I see no evidence or welding or brazing, just some bright metal where the shank was evidently milled to length. The collar wiggles slightly, and doesn't seem to be brazed in place.    

[Orlando 0]

Collar wiggle "may" be OK but if collar slides I would replace it or fasten in place.

[ArtR 0]

Remember: Numbers seen on FP are the SN, NOT a part or drawing number/revision

[matconcrete 0]

If collar slides you may have that full auto you always wanted.

[BBBQ 0]

The top firing pin is serial number K7460, bottom is 5447 (no prefix). The area I partly circled in red measures 0.95". But I can see a grind mark that shows the gap used to be 0.68". Now that I play with it a bit more the collar does slide  I can slide it to the right, but it won't go any further left (closer to the part that hits the primer) than the correct position. Well for me its a spare, might never have to use it.

[camstuff 0]

I believe Joseph Scott mentioned a few years ago that the ring is crimped into place and will crimp around some indentations machined into the firing pin.   And if it loose and slides back and forth, you will likely experience slam fires like I did with mine.