about a 4 foot flame out the end of my barrel.

Dunno whether to laugh or cry. Welcome to the world of the H335 flamethrower.

Seroiusly, many years back, 1973 to be exact I bought a Remington M660 in .308and the one load manal I had back then (Lyman) showed H335 to give the highest velocity. I guess it was high but no personally owned chronographs back then. (How did we manage?) I got a roughly 4 foot wide fire ball from it's 22" barrel and the muzzle blast felt and sounded like some kind of concussion. I made my longest shot on a deer with that rifle, 427 paces, deer running as fast as it's wounds would allow. My hunting partner hit it and it took off. It was at best a lucky shot.
So, I'm betting you get the ball of fire and I'd also bet the muzzle blast it extremely sharp.
Here's what I think. I won't say I'm right but it's what I think. I think H335 generates a great deal of very hot gas when ignited in a cartridge, especially if it's a very stiff load. (Mine were) This very hot possibly super heated unburned gas ignites with a bright flash and loud report when it hits the oxygen rick outside air.
Funy thing is I used some to work up a hot 250 gr. bullet load in my .35 Whelen, got great velocity and accuracy but no flash or extra loud bang. IIRC, a hot gad will cool if it is allowed to expand so maybe that was why there wasn't the flash and bang from the Whelen. Not saying I'm right but that's my theory FWIW.
Paul B.

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