tbirdman74 wrote:ran my first batch of 450's, some 225's and some 250's, today. and after spending the last couple of hours measuring and resetting hornady taper crimp die, was wondering if'n there ain't a better way. i have read here that most consider that .475-.476 is the apprpriate measurement for the crimp, so could we not ream out the top of the die to .475 thru to the crimp, then a feller wouldn't have to separate cases by length and reset the die for each bunch of lengths. one could set it and forget it. maybe i'm putting too much thought into it, just seems easier then what i went thru today.
There is a problem with your reasoning and I'll try to explain it as best I can.
This image is exagerated on purpose to ease grasping the concept. The current taper crimp die design relies upon you stopping your ram travel into it at some point that imparts the desired taper in the end of the brass case and it winds up also being applied to part of the softer bullet inside that case.
If you were to bore out the taper at some prescribed limit and press the case up into the limit zone, you'd wind up creating a bottle neck case and bullet.
The good news is that cases generally stop shrinking down from their spec 1.695 at around 1.675 as a worst case. That's generally speaking, but there are extreme exceptions. That's a total loss of length of 20 thousandths of an inch. That's less than the thickness of the two business cards I just mic'd, IE miniscule in size compared to the length that the taper crimp is imposed down the case, which is probably 100 thousands or more. These heavy, wide, slow by centerfire rifle standards, bullets are pretty forgiving at the performance level for variations at the cartridge dimention level. So, I'd say that while it is good practice to set your taper amount based upon the longest case you have, the resulting difference in the shortest case may not manifest much at the target board. I prep my brass and bullets more than most 450b shooters to minimize performance variation attirbutable to dimensional shortcomings or surface discontinuities when I'm doing load testing. Not just velocity variation, not just pressure sign variation and not just accuracy variation, but a balancing act between all three. From my experience, those case and bullet variations generally don't have a large influence upon performance. IE very forgiving.
I would not sweat the difference. If it troubles you, you can always trim all your cases after resizing, near the middle of the average of all of them. That will cut your variation in half right there. Then you're down to just the thickness of one business card. If you have one or two fluke cases that are way shorter than the rest, then cull them out. That's what serious accuracy fans do after weighing their cases, checking their concentricity, checking neck thickness, etc. Their calibers and bullets are far less forgiving than the 450b though.
Hoot