Its not just cylinder gap, the freebore in the bfr is a huge advantage as well, so is the rifling. Randy was barely getting 454 velocities. That said, ive seen this with many smiths as well as my own. The bfr is by far a faster better built gun. It out distances my 454?s with any weight bullet handily. 265?s are well over 250 fps faster and 300?s are 240-500 fps faster depending on loading technique. None of which is insignificant. When you add to the fact the 7.5? bfr balances as well offhand as a 10? fa83 you have something for sure. The real issue is the frrebore and the rifling. Smith does a few things that cause a velocity loss.