450B case trim length: Contradiction & Confusion

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Re: 450B case trim length: Contradiction & Confusion

Postby Hoot » Wed Sep 05, 2012 7:26 pm

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. :roll:

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.

Hoot


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Re: 450B case trim length: Contradiction & Confusion

Postby pitted bore » Wed Sep 05, 2012 8:42 pm

BD & Hoot-
I'm in agreement with your points. Hornady's published lengths, both max and trim, may be fictional.

My dissertation was intended to point out a problem with Hornady's contradictory specifications for the cartridge. I spent enough time trying to discover the basis of the contradiction that I wrote it up in case somebody else should walk into the problem as did stevewix.

The web note about trimming for FTX bullets had to be declared to be the nonsense it is.

As a side note, I really need to do a careful study of whether the cases stretch when used in the bolt guns. Certainly the chambers are not chromed.

Take care,
--Bob
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Re: 450B case trim length: Contradiction & Confusion

Postby stevewix » Thu Sep 06, 2012 9:44 am

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

The only reason to trim straight-walled cases is to uniform them, and thereby uniform their neck tension as they go through the crimp whether it's a roll crimp or a taper crimp. Once these cases get too short they should probably be culled. I agree with you BD1!

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Re: 450B case trim length: Contradiction & Confusion

Postby Gruger » Thu Sep 06, 2012 11:31 am

We should get wildcatter to develop a .40 LM cartridge (or 9mm LM?), so we can reform out of spec .450 BM cartridges to .40 LM and put the brass to a new use :P
Something like the .357 sig (parent case .40 S&W) comes to mind.

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Re: 450B case trim length: Contradiction & Confusion

Postby longnkrnch » Thu Sep 06, 2012 12:14 pm

Some of mine have actually shrunk after firing. Before 1.695, after 1.690. Hoping they'll lengthen some when I size again
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Re: 450B case trim length: Contradiction & Confusion

Postby Hoot » Thu Sep 06, 2012 12:18 pm

stevewix wrote:...snip...The only reason to trim straight-walled cases is to uniform them, and thereby uniform their neck tension as they go through the crimp whether it's a roll crimp or a taper crimp. Once these cases get too short they should probably be culled. I agree with you BD1!

Steve


Steve et al,

WRT the taper crimp die and the need to precisely trim for precise tension, a length variation of .010 or less (think playing card thickness) will not have as much impact upon the degree of retention from the taper crimp as the normal variation in hardness from one manufacturing lot of brass to the next or even how many times they've been resized. If you segregate your brass by lot and by the number of times it has been resized, you'll do more for the taper crimp tension consistency than trimming alone. That having been said, if you trim as well, you do normalize the length of the case all the way around and that is always a plus.

My experience has been that the fired and resized case length varies a little. I never explored why, but I have observed that when I begin trimming, the trimmer will generally remove brass first from the longest part of the case and gradually remove more and more brass around the total mouth circumference until it is removing brass from the entire circumference. To me, that implies that aside from the chance that your trimmer or pilot are out of round, that the cases do not shrink lengthwise, evenly all the way around when fired. Whether that is the result of an assymmetrical chamber, assymmetrical brass manufacturing, or whatever, it is nonetheless a phenomenon I see all the time. When measuring a fired case, you can also get different readings when you rotate it as an indicator of uneven shrinkage. I don't recall that amount ever being more than 2 to 3 mils though.

I enjoy the art of reloading and any steps I can take to reduce variation from one case to the next, is time well spent. I do however realize that value is in the eye of the beholder. ;)

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Re: 450B case trim length: Contradiction & Confusion

Postby Draino » Fri Oct 13, 2017 7:13 pm

Well, isn't this just dandy?

Im using a mixture of factory loaded Hornady ammunition and Hornady brass, and I can confirm that my brass grows after resizing in most cases, betwee, .001 and .003 in length.

Im shooting out of a Ruger Scout. Perhaps its chamber is rough enough to hold onto the brass? I'll have to have a look. Im only just getting brass long enough to meet the 1.695 length after two firings.
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Re: 450B case trim length: Contradiction & Confusion

Postby plant_one » Fri Oct 13, 2017 7:33 pm

Draino wrote:Well, isn't this just dandy?

Im using a mixture of factory loaded Hornady ammunition and Hornady brass, and I can confirm that my brass grows after resizing in most cases, betwee, .001 and .003 in length.

Im shooting out of a Ruger Scout. Perhaps its chamber is rough enough to hold onto the brass? I'll have to have a look. Im only just getting brass long enough to meet the 1.695 length after two firings.


can you give us some more load data?

are you crimping? if so to what dia? what bullet? powder charge, etc
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Re: 450B case trim length: Contradiction & Confusion

Postby Draino » Sun Jan 28, 2018 10:49 pm

I need to visit the site more often!


COAL 2.12
LilGun at various loads from 39.0 all the way up to 49.0 using 225 FTX's. W296 for testing 300XTP's from 33 up to 39 grains. I have crimped at .476 down to .473 during all this development. Last night I selected some mixed brass to test: Some heavily sooted from light load testing on the 300grainers, and some of the 225FTx stuff that was loaded so high Id get unburnt powder in my eyes, but one heck of a clean case on extraction! Some of this brass was factory loaded stuff, some was Hornady unprimed brass.

(FWIW I stop testing at the first signs of flattening primers or bolt lift issues. Even as high as 49.0grains of LilGun, the Ruger Scout 77 action opens and extracts as if its factory ammunition. Amazing)

ANYHOW, I took measurements before resizing. Some pieces were 1.685, some were still 1.694 after firing. Regardless, after a quick clean and some hoem made Lanolin lube, these pieces ALL resized between two and three thousands LONGER.

I have no idea why. I can only assume the heat being transferred immediately to the chamber of a bolt action has some cooling/restructuring effect that semi-automatics dont have as the brass is turfed out hot. I wish I knew more.

I dont know where to measure at the web area to get a correct err....whats it called, 'case head expansion?' measurement, but at the lowest point before the extractor groove, IIRC it was .503-.505 I think. I will check again though.

Can
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Re: 450B case trim length: Contradiction & Confusion

Postby Hoot » Mon Jan 29, 2018 6:19 am

Draino wrote:...snip... I dont know where to measure at the web area to get a correct err....whats it called, 'case head expansion?' measurement, but at the lowest point before the extractor groove, IIRC it was .503-.505 I think. I will check again though.

Can


Set your micrometer to say .5000 and slide the resized, clean case through from front to rear. If it has been shot at least once, it will drag or catch where the widest spot is and that's usually right where the web transitions to the wall. That's the area of interest. Once that area exceeds .5015 or so, you run the risk of it seizing or dragging and preventing an AR bolt from rotating into battery, depending upon how tight, or not, your chamber is. If it fails to pass at .5015, it's scrap brass. Bolt actions in theory (see sig), will be more tolerant as you can cam the round into battery with more closing effort. Best to find out which cases are going to be problem children before you load them back up. Again, this is more of an issue in an autoloader. My clean chamber seizes cases at .5017, so not wanting to have issues at the shooting bench, I toss any case when it can't pass through the micrometer when set to .5015, to allow for soot fouling after an extended shooting session.

I grade my resized, clean cases into different peanut butter jars at .5000, .5005, .5010 and .5015. When choosing which ones to reload for a project, I usually use the .5015 ones for foulers and the .5005-.5010 for keepers. The .5000 are saved for hunting rounds, where I don't want anything to go wrong.

Hoot

Sorry to say this but IMHO, measuring this dimension is a job for a micrometer, not a caliper.
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