Power Pistol Bark/Flash in 9mm... doesn't this mean the powders too slow?

[Walkalong]

And for 16"-17" carbine load testing I have been doing, bullets should be slowing down the last 10 inches or so of the barrel.

They do when using fast powders. Not a slow enough burn (Short pressure curve) and not enough volume of gas to take advantage of the longer barrel.

 

[Jonesy814]

I use H110/Win296 for full blast 357 loads which gives an impressive flash and bang. Frequently I will use Power Pistol for midrange magnum loads because it still give me a big flash and bang just like the full blast loads!

 

[Dudedog]

If you like flash and noise in 9mm try Loudshot..rrr I mean Longshot
In informal testing I would say it's louder and flashier than PP.
(works great for Full Power stuff though )