COL question with different bullet shapes

[jamz]

I've loaded a thousand or so cartridges in .38 special, and the bullets I've used so far are conical, with a flat point, in 158gr. Picked up new bullets today, these are round nose, with a sligh flat point, also 158gr. The old ones had no cannelure, the new ones do. Without readjusting my dies, it's seating the new bullets down to about 1.45" rather than the 1.480 that the book recommends, but the case mouth is RIGHT on the cannelure- it looks good. If I seat it to the COL that the book recommends, the cannelure is way up above the case mouth.

Both sets of bullets are copper plated. My question is, do I seat it to the recommended COL and forget about the cannelure on the bullet, or shall I seat it so the case mouth is at the cannelure, and figure they chopped random amounts off the point of the bullet when they made it so COL doesn't matter anymore?

-James

 

[brickeyee]

If the load is for the bullet you are using, seat to the COL.

 

[Peter M. Eick]

The problem with different col's and different bullets is about the volume inside the case and the powder charge. Think of it this way. It is a lot like a car engine in your gun and each piston is a chamber. If you go to a shorter col, it is like pushing the piston up further and the gas -air is compressed more and tends to burn hotter faster with higher pressure. This is a big problem with the little 9mm since it works at such high pressures anyway.

To me, the concern is going shorter.

If I were you, I would test seat a bullet to the cannelure or to the maximum COL that will fit in your revolver. I would start over at the starting load or 10% down from maximum and rework up the load.

Safety first!

 

[jamz]

I wish I could find an older bullet around- I'd compare how deep the canneulure mark is compared to how deep the others have seated. I don't have a bullet puller, however, and only had a couple of non-loaded bullets, now awash somewhere in the house.

-James