[p35]

THe other day I got out my prison-surplus 870 for a check. When I unloaded it, I found that one of the shells had loosened at the crimp and was leaking white plastic buffering powder. Looked like the plastic had shrunk. This was Federal Express 2 3/4" #1 Buck, probably 10 years old (I bought up a bunch at a going out of business sale). Kind of a mess to get out of the gun. Anyone run into this before? Any ideas as to cause?

[sm]

Nope.
Have SG shells 20+ yrs old, ( some I even reloaded back when...sigh).Fed, Win, Rem kept in some SGs 20 yrs.
Makes me wonder if oil, especially penetrating oil got to ammo.

[Navy joe]

I'd say that the amount of time it had been loaded was a factor, take any shotshell and leave it stuffed in a mag tube long enough and it will deform.

[Dave McCracken]

This is frequent with ammo kept under spring tension for a long time. Use that ammo up and reload with fresh.

Not limited to Fed fodder, BTW. And some rounds telescope too.