First, before I reload a batch of brass I check for OAL measuring with a caliper from case head to case mouth. - OAL is not super critical but I don't mix new brass with brass that has been fired several times. - So, I'm working with a "range" of uniformity in my brass for starters. Then I go through the steps of Sizing Clean brass, Priming, On Revolver brass (bullet dependent) I bell the mouth the appropriate amount to be able to seat & crimp bullets, Throwing Powder charges, then seat the bullet and I use a die that crimps as part of the seating operation.
So, to be a bit more specific, On a 500 S&W with a full house load (440 gr. Cast Gas-Check) I will run a "Heavy crimp" and the bullet actually has a crimp groove to facilitate a roll style crimp. Also after I've seated & crimped, I'm going to raise the Ram on the press and rotate the round in the shell holder approx. 90 degrees and then run the round back up one more time. - I'll inspect it with a magnifying glass when I set my dies up so that I can get a close visual look and insure that I'm achieving a good crimp. - The "acid test" is to fire 4 rounds of the 5 in the cylinder, then open the cylinder and pull the unfired round to inspect for bullet movement.
The example that I gave with a 500 S&W mag. is what I do with other Magnum revolver calibers. - Magnum revolver loads that are using large charges of ball powder rely heavily on a good heavy roll crimp to achieve uniform results (accuracy & velocity S/D).
Now, lets move on to the rimless cases that employ the taper style crimp. - As was stated by another member a good crimp for a semi-auto is also important. - The requirement to have pressure build and have uniform results is what we seek as well as to not have bullets be pushed deeper into the cases. - A taper crimp will not have the holding power that a heavy roll crimp has but it is more than sufficient for the ammunition it is used for (45 ACP, 40 S&W, 9mm, etc.) - Of the 3 die manufacturers that I've used (Redding, RCBS, & LEE) All have instructions on how to set up the crimp whether it be the taper crimp used for rimless type ammunition or the roll crimp which is employed on rimmed revolver ammo. - The taper crimp if the die is not set correctly can deform or start to buckle the brass if it is over crimping. Under crimping can be identified by not having bullets that "show" an image to some degree on the outer part of the case and the bullets may be looser than is desirable, so press the nose of a loaded round against the work bench top to see if bullet movement can be detected.
Crimp also is one of the steps that "feel" is acquired after loading hand gun ammunition. With practice one can tell if the crimps being applied are good and also a close visual inspection from time to time during the process of loading ammunition.
It is also one of the reasons I don't mix brass up or load 5 times fired brass with new or once fired brass, because the die for crimping and bullet seating most likely will not be optimally adjusted. - To keep from having to adjust bullet seater / crimp dies one can employ the use of shims under the die lock ring.
I've loaded hand gun ammunition for 50 years using a single stage press set up which surely is not as quick or efficient as the progressive machines do, but its all the same concept and the fact remains that we as reloader must know and understand the individual steps and our equipment that performs those steps to produce good quality ammunition that functions flawlessly though our hand guns (and rifles).
How do you monitor your crimping process to know if it’s delivering the desired outcome?
Through proper use of the dies, close inspection, and actual checks of an unfired round after being subjected to recoil from previously fired rounds. - Also, how well did the load perform, did it shoot accurately at my chosen range ?
My efforts in response are Not to belittle anyone, and I don't want to sound like an "old grouch" - I wouldn't have posted on the thread if I didn't have something of benefit to say. - Also, I don't consider myself as the be all for all expert. - I come here to learn and to share.
All The Best - Ron -
