Bullet seating: While this can be done in combination with applying a crimp, I’ll take the subjects one at a time (many like to crimp in a separate step anyway). Like I said before – setting up dies can be a pain. If you’re on a turret or progressive press, you’ll likely get the die set up and never touch it again. If you’re on a single stage or using multiple bullet profiles, I think it’s wise to make a dummy round first (no powder or primer) so you can easily set up the die in the future and not have to fiddle around as much. One thing you’ll notice as you get going is that your overall length (OAL) isn’t always coming out the same. The one you set up the die with was perfect, but the next was a few thousandths shorter or longer. This is normal. The bullet profile will vary a little in the manufacturing process, even with match bullets. Something with a flat nose and a flat seater plug will be more consistent. It will start to drive you nuts when you’re dealing with soft point spitzer bullets in rifle. Get your die set up to make sure the long ones don’t exceed the listed maximum OAL and stop sweating it. That extra thousandth of an inch won’t make a bit of difference.
Taper Crimping (Auto loading handguns): The important concept to walk away with here is you aren’t trying to squeeze the bullet. All you’re doing is removing the flare you put in the case to start the bullet. A taper crimp doesn’t provide any neck tension… that comes from step 1 - sizing the case. In fact, if you go too far the case will buckle and you’ll have less neck tension. Again, you just want to remove the flare you put in the case. So how far do you go? A decent rule of thumb is the thickness of the brass times two, plus the diameter of your bullet. Another way to test is go in small increments until your loaded cartridge drops freely into and out of the chamber of your barrel (a lot easier and safer if you take it out of the gun first). You also want to make sure the cartridge sits flush or slightly below your barrel hood. If it sticks up above it, something is wrong (probably isn’t crimped enough). This has been referred to as the “plunk” test. There are also aftermarket gauges to test your cartridges if you feel you haven’t spent enough money at this point.
Roll Crimping (Revolver and Rifle cartridges): A roll crimp actually does hold the bullet in place, but it’s still not exactly neck tension. You’ll see bullets for rimmed cartridges like .357 mag or .44 mag that have a groove or “cannelure” in the bullet to crimp the brass into. The big idea here is that with hard-kicking magnums, the recoil impulse can actually yank the other cases in the cylinder back hard enough to begin pulling the bullets out (known as jumping the crimp). If this goes far enough, it can lock up the action of the revolver – not something easily fixed in the field. Another purpose of a good roll crimp is to hold on to that bullet a microsecond longer to get a good consistent powder burn, as many of these cartridges use slow burning powders. Some rifle bullets will have cannelures, but you’ll get mixed opinions on whether or not to roll crimp a rifle bullet. It can help prevent the bullet from moving when being battered in the actions of auto loading rifles, but some argue it can also be detrimental to accuracy. DON’T roll crimp a cartridge that headspaces on the case mouth or on a bullet that doesn’t have a cannelure. Bad juju. There is a little bit of a touch element to roll crimping that can’t be taught. To little doesn’t do any good, too much can wreck your case and bullet. Like most things here, you’re just going to have to do it a few times.
Reloading for rimmed handgun cartridges: This process is the same as what was described above, but you’ll likely roll crimp instead of taper crimp. Also, you’re more likely to want to trim your brass so they are all the same length and line up to the cannelure consistently.
Last edited by Zombie Steve; 05-18-2011 at 00:49..