For the longest time (like, 16+ years), I’ve loaded solely with the seating die that came with my Dillon die set. Considering that I’ve pretty much always used the same bullet for an extended period of time, I didn’t have a lot of need to adjust seating depth frequently. I’d always felt the CSD was a “nice to have”, but not necessary. I decided to try one out to see if I could improve upon my ammunition accuracy and consistency.
Aside from the adjustment micrometer, the biggest difference between this die and most seat dies is the CSD’s ability to better align the bullet to be exactly centered on the case, and to insure the bullet is exactly straight when it’s seated into the case. I failed to do a really solid examination of group sizes, and such, but I can say that my groups appear to have shrunk slightly at 25 and 50 yards. Not extreme – it’s not night and day, but enough to be noticeable.
The die also made setting up the new press a joy. I hadn’t anticipated how much easier adjusting bullet depth would be with this die, but it makes sense when you think about it. With the standard Dillon die, the process involves loosening the lock ring (without changing the die adjustment), adjust the die in the correct direction, then re-tighten the lock ring (again, without changing the adjustment), and check the adjustment by seating a bullet. If you went too deep, you’ve now ruined a case and bullet (or you’re pulling the bullet). Rinse and repeat until you get it right – and you’re usually settling for something within a few thousandths of where you want to be, but not dead on.
Enter the CSD. Insure the die is set to seat really long. Test seat a bullet, and measure the OAL. Subtract the desired OAL from the length indicated on your caliper. Adjust the die shorter by the difference. Bang. You’re done. Well, mostly – there’s one caveat. If you’re using a compressed load, you may have to adjust the die deeper than the math would suggest. This is because the powder charge will tend to push the bullet back out a bit, so you have to start by seating it deeper than the desired OAL with that in mind. It’s still remarkably easy with this die, though, because you won’t ever adjust it too deep by mistake.
If you happen to change bullets with any frequency (bullet style, weight, shape, etc), this die is a huge boon to speed of set up. You just set up your depth once for that bullet, and write down the setting. The next time you load that bullet, you just dial the micrometer on the die to that same setting, and away you go (you would obviously double check OAL after changing the setting, but it seems to be very repeatable on my die).
In the end, this die is very cool stuff. It’s not strictly required equipment, but it’s benefits are a very solid improvement over the standard gear. I plan on using one of these dies consistently in the future.