Last week I wrote about the effect of bullet seating depth (bullet jump) on performance. The bottom line was that it didn't seem to make any difference. Since then I did another experiment looking at two new (to me) powders and the effect of crimping. Crimping is where you pinch in the case mouth just a little bit over the cannelure (groove) in the bullet. My range test indicated that crimping made for a more accurate cartridge.

The way I do this is to seat the bullet to the proper depth with one die then using another die set the crimp. It takes a little adjusting (dealing with thousandths of an inch here) but in the end it comes out right.

In the photo, the scale is on the left in tenths of an inch. You can see the cannelure is about 0.050 inches. On the left is one attempt to get the case mouth up to the top of the cannelure. One final adjustment and I had the case mouth (bullet seating depth) exactly how I wanted it. In the final photo you can see the crimped cartridge. There is a very tiny radius at the top of the mouth where the case is pressed into the cannelure. The main purpose of crimping is to keep the bullet fixed in the cartridge. If it is not crimped, cartridges in the magazine or cylinder can have the bullet displaced from the effect of the recoil. This has happened to me with a high power .44 magnum load.

Can't wait for the weather to improve so I can head out to the range.