carrier dog spring
My outfit bought a number (a dozen or so) of 870's that were not "police " guns, but were not marked "wingmaster " or "Express" guns either. Seems like they were simply marked "Magnum" w/ parkerized finished.
This would have been about 20 years , back, say early '90's. About half of those guns developed feed problems, the fresh round not being elevated enoough to reliably hit the champer mouth, this problem solved by installing a new dog spring. The remaider of the guns got new springs before probs developed.
I hear and see discussion indicating that the std dog spring has been eliminated and all the dog springs are HD. I dunno, but our guns run better now with new springs, installed in the past couple of years.
My 30 yr old Wingmaster is getting a bit finicky, and sluggish lifting shells to the chamber mouth. I am considering a dog spring for it too.