Bearing Surface

[Whitespider]

:coffee:
I did a quick search, didn’t find an answer for this.

I was lubing some Lee Tumble Lube boolits this AM, and started to wonder about something. Looking at and comparing the bearing surface of the TL verses a more traditional, single lube groove design. I started to wonder how much effect the difference in bearing surface would have on velocity, and therefor pressure. To “test” this I would need another boolit of the same weight, and same approximate base to front driving band length.

I was going to shoot both designs, with identical primers and powder charges, over my chronograph. The TL boolit I have is a .41 caliber SWC, the only other .41 I have is a commercially hard cast SWC. The dimensions and weight are close enough, and I could remove the lube and use the same stuff I lube my TLs with. But the alloy is not the same and the hard cast are about .001+ undersize for my gun. After some consideration I decided my “test” wouldn’t be valid.

Has anyone “tested” this, or read anything about this? Does the TL design have a significant effect on pressure and velocity? Higher? Lower?

[shooter93]

Assuming correct bullet fit...more bearing surfce means more friction which means more required pressures. From that point on it's a matter of how well the lube works for the velocity, pressure involved. If you have hard heat treated bullets and drive them as fast as possible with one of the super lubes...then load the same load with something like liquid alox (an excellent lube for certain things) the pressure increase can well be into the dangerous zone.

[Onlymenotu]

acctual i was pondering the same ?... so why not make a mold of a said cal and make crimp grooves,,, basicly all the way down the boolit,,, to the end so the boolit could be seated in or out to any depth and use the crimp grooves as lube rings.....