SB15's hybrid
That comment was made a while before your 11x test _Fnord. Unless you're actually trying to achieve detonation, it is very difficult to do so with propane/air. While detonation can cause even strong steel chambers to fatigue and fail after a few shots, actually incurring detonation is rather unlikely.
Spudfiles' resident expert on all things that sail through the air at improbable speeds, trailing an incandescent wake of ionized air, dissociated polymers and metal oxides.