Having a massive barrel/chamber in a roon temperature pneumatic is fine if you're using heavy projectiles, but room temperature air won't exceed the speed of sound by a great degree (It shouldn't exceed the speed of sound whatsoever, but it does sometimes)
Anyway, since we're on this topic, I have one of these
and a twelve foot 3in barrel.
I don't think I could bring myself to wreck it, the appeal of a large shop compressor tank is too great.
And does anyone know the standard threading for such a bottle? It looks like 3/4 NPT/BSP/something, it's not LH, but that's all I can tell. And before someone tells me to measure it, my vernier calipers don't fit in the valve protecting ring.