What could cause this much muzzle residue?

[Joe L]

Atlanta's 147 reload is rated 850 fps 130 pf out of a G17 4.5" barrel

Lawman 115 is 1200 fps 138pf and loads their 147 to 985 145pf, both out of a 4" barrel.

Same lot of Atlanta 147's used in both guns?

What is the length of the sig and cz barrels?

I doubt the chamber dimension makes that much difference especially if 'the little end' is the same.

Does Atlanta use mixed brass in their reloads?

Any military cases in there?

Plated verses fmj bullets?

Lots of variables to be considered.

btw fast burning powders like AA#2, Bullseye etc tend to be really dirty in light loads.

Temperature is a direct function of the pressure formula given the same volumne.

Truborshooter,

I think I've made a bigger deal out of the residue than necessary. I don't understand why it builds up much quicker on the CZ than on the SIG, but the gun is very accurate with any ammo I've tried including the Atlanta Arms 147. I am going to go back to 115 for a while and then decide what to change, if anything. Atlanta does mix their brass, and I shot the same lot out of both barrels, which are within a 0.1 of same length.

Joe