On the 4th we had a bunch of people out to go shooting. And of course our pride and joy is a full auto m16 currently set up as a 14.5 m4.

Anyway, it's never had any issues before but literally the first mag that day it would fire a few then fail to set off a chambered round. Over and over, for several mags. So I started looking closer and it and noticed what looked to be the smallest little sliver of brass next to the hole for the firing pin. Couldn't have been but a hairs thickness. Anyway I knocked it out with a small Allen wrench and the gun was fine the rest of the day.

Doesn't make much sense to me that this basically non existent splinter would sideline the rifle. Could there be another issue?

All Colt upper, 14.5 socom barrel.

A piece of metal that interferes with the firing pin's movement can do exactly what you describe.  It could be a bit of case material, some bits of blown primer, or almost anything else.  All it takes to get a light strike is to slow down the firing pin just enough.  Remember, the firing pin floats; only the firing pin's inertia allows it to strike the primer hard enough to fire the primer.

I've have been experiencing alot of failures recently...i thought ive seen it all..recently a tiny sliver of brass ended up between the firing pin and primer. I was suprised because i had never had it happen...I thought it might be  soft primers, recently i noticed  my firing pin is ruff/worn. It might have been the cause.
I have received out of spec firing pins before, but this may be my first time wearing one out or had enough to be replaced.