450Bushmaster.net

Has anyone done any experimenting with the effect the length of bullet shank in contact with the rifling on pressure and velocity? I only have eight different projectiles, but they all have a different BS length. I made a crud measuring device from a sized .45ACP and only opened the mouth to .4508.hen inserted bullets nose first. This allowed me to measure the BS. Here is what I have. 200grn COP .367 225FTX .307 230FMJ .282 245H Innerlock .368 250FTX lead .378 250FTX Monoflex .522 275XPB .439 275TSX .472 . As you can see there is big difference in BS length. The only testing I have done so far is with the 250Mono in Ruger Gunsight with its 1/16 twist pressure spiked quickly.Hope todo a lot of experimenting when weather and chrono get fixed. Any thoughts or is this just so much BS? LOL

Quickload has a variable called Shot Start Initiation Pressure. The pressure to overcome pull-out resistance AND engraving into rifling.
Standard Rifle:
Jacketed - 3625psi
Solid soft brass- 1800psi
Solid copper- 6525psi
FMJ with hard core- 6525psi

Handgun:
Jacketed- 2175psi
Lead- 1160psi

I'm not sure if this is what you were looking for or not.

Not precisely related but an interesting parallel. About 9 years back, I plated some Barnes XPB bullets with HBN, which is commonly used in bottleneck calibers for benchrest shooting. The velocity went down, confirming the importance of resistance to movement down the bore in order to keep the pressure optimal. Now those velocities didn't change in quantum leaps and bounds but they definitely went down on average. That was using a 20" 1:24 twist, chrome lined Bushmaster barrel.

Hoot