BD1 wrote:I'm going to go out on a limb here and suggest the the trim to length of the .450 Bushmaster should be 1.70, the same dimension as the case length spec, and in fact you should never need to trim a Hornady factory .450B case.
I make this bold statement based on two factors: First, all straight wall cases get shorter every time they are re-sized, in my experience this is true across the board with no exceptions. There is no need to trim them once they are within spec. Second, I have never heard of a reported Hornady factory .450 B case longer than 1.70. if anyone has experienced such a case, please report it here. My problem with Hornady factory cases is that they become too short, (under minimum length for correct headspace), long before they wear out or split.
I have never trimmed a Hornady factory case, and have no intentions to ever do so.
BD
+1 again. I have never trimmed a Hornady case for this exact reason, aside from the 20 that I annealed and then only for the purpose of having them all start out the same length for behavior comparison. I have had them come new in the same box ranging from 1.70 down to 1.689 with the lower value being the exception. Never over 1.70, but they sure don't worry if they're shorter than 1.695. After the first firing, they then ranged from 1.679 to 1.692. After the second, they ranged from 1.669 to 1.689, but more were in the 1.675 to 1.685 range. After the third firing, they were all 1.685 or less.
Here's the kicker. The hotter you load them, the less they shrink. I personally believe it's because they chose to chrome plate the chamber to make maintenance easier. Mine has around 1600-1650 rounds through it and the chamber still looks like glass. That's got to be harder for the brass to hold onto when they're loaded lighter than one that just has a lustrous finish I would expect from simple CrMo or SS. That's speculative though. When Hornady chose to go away from the thicker .284 Winchester type brass that Wildcatter's design was based upon to the thinner stuff that they sell, they knew exactly what would happen and what they were doing was assuring a continuous revenue stream. Don't kid yourself.
When mine get below 1.675-1.680, I stop using them to develop and prove out loads. They're still very shootable though. In the interest of avoiding histrionics, the variation from 1.695 to 1.685 is the thickness of one playing card. That's not going to break this gun, nor with the thickness of 2 or 3. After they feed into the chamber being pushed ahead of the extractor, then bounce off that lip and the extraction hook picks them up, it pulls them back, snug against the bolt face anyway.
This same arousal and debate ignites over the .45 ACP, which behaves similarly, time and again.
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