I recently bought a case of Federal XM193A (came packaged in black American Eagle boxes) from ammoman, and was surprised by what I saw at the range this weekend. I know these are loaded to “military spec”, and the previous case I got showed signs of high pressure (flattened primers, extractor marks). But the shells from this recent lot show signs of way excessive pressures. Out of a box of 20, I had one primer completely blown out, and had a few shells with clear signs of gas leaking from around the primers. I think I might pull the bullets, measure the powder, and try and build up a load with a little less powder.
Is your AR barrel stamped 5.56mm? The NATO chambering is to a different tolerance than the SAAMI chambering–or the 5.56 and .223 respectively. XM193A ammo shot in a .223 Remington (SAAMI) chambering will cause dangerous back pressure.
You can safetly shoot .223 in your 5.56 AR, but not 5.56 in a .223 rifle.
Just a thought…
I’ve fired literally thousands of rounds of Federal Lake City XM193 out of a number of different AR15’s I built. I’ve never even once experienced what you’re seeing. I would be highly concerned that you have headspacing issues, chamber issues, or something else with the weapon you are firing these out of.
Jephnol was right,
If I’m not mistaken your shooting the 5.56 ammo out of the Krieger AR-15 Varmatch barrel which I presume you purchased in .223 cal (.224). (You need to check to see what it says in your paperwork).
You can’t shoot 5.56 ammo in a 223 barrel ( you can shoot 223 in a 5.56 barrel)
I’m glad you weren’t hurt.