Cannelure size and ignition?

[Blackwater]

If you were designing a bullet for a Mtn. Mould, would you use the .045" crimp groove, or the .055"? Will the larger size crimp groove allow at least the option of a heavier crimp, and if so, does a heavier crimp help retain the bullet in the case a tad longer, thus getting the pressure up for (sometimes) a better powder burn? Just fiddling around right now, but .... soon. Once I "design" and order one, and it shoots, I'll have enough confidence to do more, of course. Thanks for any help/insights.

[olemiss]

I have several molds from Mountain Molds. I use the 0.055 inch crimp groove on calibers between 41 and 45, and that seems to work fine. For the 5-shot 45 Colt (or 454 Casull) the 0.055 inch crimp groove barely keeps the bullets in the case for my 350 grain bullet, and I have to use a very heavy crimp. For the really big bores, like the 500 Linebaugh, I use the 0.07 inch crimp groove which allows more crimp to keep the bullets in the case under recoil. I have not noticed any differences in "powder burn" with different crimp groove lengths, but if the bullets start wandering out of the case under recoil, velocity and accuracy will deteriorate rapidly.

[Bass Ackward]

If you were designing a bullet for a Mtn. Mould, would you use the .045" crimp groove, or the .055"? Will the larger size crimp groove allow at least the option of a heavier crimp, and if so, does a heavier crimp help retain the bullet in the case a tad longer, thus getting the pressure up for (sometimes) a better powder burn? Just fiddling around right now, but .... soon. Once I "design" and order one, and it shoots, I'll have enough confidence to do more, of course. Thanks for any help/insights.


Blackwater,

I actually prefer the .070 long if I am designing a one diameter bullet so that my crimp is a fold and not a crimp crush. This also has the added benefit of shifting the weight and center of balance back. You can see this in the picture when you change it if you watch. It doesn't work on light for caliber bullets because the extra weight from length takes width off your drive bands.

But my handgun bullets are two diameter now. Let's say I was looking at a .357 and building an olgival. I would then drop the front band diameter to .354 and only use the .055 crimp. (On 44s as an example, I drop the front band to .426, back bands .434.) My back bands would be .358 after sizing, so what I am now doing is folding over and down for a stronger crimp much like crimping over an olgive or front shoulder. The crimp from hell without damaging bullets or brass. As the bullet sizes in the bore, the bands will shift back naturally and move that center of balance for me even more.

I can chamber larger diameter bullets without hanging up the cylinder since all my guns are tight with little end play and tight headspace. It also allows more time for the cylinder to work into alignment before damaging the bullet surface so I don't need as wide a front band to handle this impact, again shifting weight back. The side benefit I get is less bore friction on the front band so that the bullet can better utilize lube left in the bore from the last bullet.

This whole process takes weight off the front of the bullet moving the center of balance back making a more aerodynamic bullet by having a longer bullet for the same weight in the process no matter how wide my meplat is. And the front area still drives hard enough at handgun RPMs. I get wider load flexibility with each powder and accuracy across a wider velocity spectrum that way without having to hollow point everything. Plus lube choice isn't as critical either.

Ain't it funny what a crimp will do for ya? :grin: