Sooty cases in 9mm carbine

[tcoz]

I hope someone can satisfy my curiosity about this...
I have a relatively new CZ Scorpion Evo 9mm carbine with a 16" barrel. I've loaded Bullseye, Titegroup and HP-38, all three in medium loads. The same loads are fired in a Sig P938, SA Range Officer Compact and the carbine. The fired cases come out relatively clean from the pistols but they come out of the Scorpion pretty sooty. Does anybody have an explanation for this? I'm not concerned, just curious. I'm thinking it must have something to do with shooting a pistol round in a carbine with a 16" barrel.

 

[LiveLife]

Sooty cases are normal for blowback carbines.

I am testing 100/115/124/147 jacketed/thick plated bullets at mid to max jacketed load data from Bullseye to Longshot using 17" Just Right and 16" PSA carbines.

 

[tcoz]

bds, I've been following that thread. Very interesting and extremely thorough. Thanks for your efforts.

 

[Walkalong]

In my blow back 9MM AR 15 the slower powder, higher velocity, loads tend to be sootier than the faster powder loads that get to pressure quickly and burn faster. My N320 loads are just a little sooty, but they also gain nearly nothing in FPS from a 5" barrel to a 16" barrel.

But yea, a AA #5 9MM load that leaves brass clean in my 1911 will be real sooty fired in the AR.

 

[wbbh]

As BDS pointed out, a blowback versus a locked breach. I have the same experience with reloads (TightGroup powder) and factory ammunition in my Beretta CX4 9mm carbine and with the high pressure 5.7x28 round (CFE Pistol & True Blue powders) in an AR57 upper. On the good side, the carbon is easy to clean up. It's like a layer of greasy dirt versus the baked on carbon on an AR bolt tail.

 

[egd]

I've noticed the same thing in my Colt AR-9, as I call it.