[Big Friend Ten (BFT)]

A good analogy Charlie!

A couple years ago I measured the pressure on promotional Federal and Winchester 12 gauge cartridges. From the same box the pressures varied more than 1000 psi between individual shells.

The figure below shows pressure traces from two handloads in which I varied only the type of shot.

Traces 1-5 were with lead shot where a spread of almost 1500 psi and mean of 6658 psi. Of these T5 was 700 PSI above the highest of the other four traces (shells fired). There could have been something very minor which caused this 10% pressure increase such as a stronger crimp.

Traces 6-10 (T8 didn't register) were with ITX shot (which is harder than lead) where a spread of only 627 psi and mean of 9771 psi.

What I learned from this was that with the hulls, wads, primers, and certain amount a specific powder, an equal weight of ITX would cause a 32% pressure increase. Had I thrown out trace T5 the pressure increase would have been even higher! Also notice that there is only a range of 600 psi difference in the IXT loads. Perhaps the higher pressure caused a more efficient burning of powder?