OAL, Seating depth, and lube grooves

[trucker76]

So today I was rolling up some 44 mag with the new Lee 240gr TL SWC boolits I cast up. I managed to find a lyman cast load manual at a local shop for load info. They didn't have a load for this bullet but they did have a 240gr load info. I got to thinking about oal and seating depth. Now I've read that the deeper you seat the bullet the higher the pressure will be in the case since deeper bullet = less case volume. Hence you have an OAL measurement. But what if your bullet is a different length that the bullet used in the load data? So I tried seating the bullet I had to the OAL listed in the load data (1.645). At that depth there were 2 of the little TL lube grooves above the case. Should this bullet be seated so all the lube grooves are inside the case? Or is it ok to roll crimp it with a couple grooves above the case mouth?

[Larry Gibson]

In Magnum cases I seat my own TL430-240-SWCs so the crimp is in the front lube groove. I do this because I size and lube them at .430. My Ruger and Hawes have tapered cylinder throats so they can take the bullets seated farther out but my Colt Anaconda has .429 untapered throats and the TC Contender has a minimal throat length. Thus the shorter seating in Magnum cases.

If you are using a maximum load out of a manual then the seating depth can be a concern. However, if you are starting at the "start" load and working up and will stop at the 1st sign of excessive pressure as per the manuals then a variation in seating depth is accounted for in the "work up" load development. Obviously "working up" loads is the best method and is why all manuals suggest it.

Larry Gibson

[trucker76]

Ok thanks. Yes I always start at the minimal load and work up.

[Larry Gibson]

Excellent, just crimp in the 1st or 2nd lube groove and load 'em up for testing.

Larry Gibson