With all due respect, doesn't "Hey, my gun was really dirty, jammed a lot, and didn't always fire. Must've been the ammo" sound a bit silly to you?
Dirt in and around the chamber can prevent a round from seating fully. Some of the energy from the firing pin blow is then used to fully seat the round, meaning the actual blow from the pin against the rim is significantly lighter. In a truly dirty gun, the firing pin movement can itself be retarded by gum, grit, etc.
You might have bad ammo, though I am unaware of Federal having a reputation for unreliability. What you do know is that your gun is dirty. Clean the gun to rule out (or in) the obvious problem, then worry about the ammo.