Barnes 200gr XPB and 275gr TSX

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Re: Barnes 200gr XPB and 275gr TSX

Postby mcb » Tue Jul 25, 2017 6:30 pm

Bmt85 wrote:Resized Remington 405gr?


Yeap

I don't have a set of micrometers so I did the best I could with my good Mitutoyo calipers.

Once fired Hornady brass fresh out of my sizing die:

.4990
.4995
.4990
.4995
.4990

The 37.5 gr Lil'gun, 200gr PBX load:

.5005
.4995
.5000
.5000
lost one

The 39.0 gr Lil'gun 200gr PBX load

.5010
.5000
.5005
.5010
.5000

I have not trimmed my brass at all yet so I am not sure case length data will help much here. I have never tried to monitor Case Head Growth. I have done a ton of reloading but to date is almost all pistol (to feed my USPSA addition) and shotgun so I would be grateful for an interpretation of what the above data might indicate. Always looking to learn. Thanks!
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Re: Barnes 200gr XPB and 275gr TSX

Postby Hoot » Tue Jul 25, 2017 7:51 pm

Were those resultant case head growth numbers before or after resizing? They usually get a little narrower and a little longer after resizing. Now, if those dimensions are after resizing, you have about one more repeat of those 39gr loads before the cases will start binding in the chamber on the next reload. I'm guessing they were before resizing. You have a learning opportunity if you're up for it. Mark them and also measure the length. Wipe them off with a rag with a little mineral spirits or other mild solvent on it, dry them, lube and resize them. Then take the diameter and length measurements again.

All that having been said, You strive to keep the case head diameter growth to less than .005 increase that doesn't resize back at the most. Otherwise, you'll hit the diameter wall in about 4 reloads. Tamer loads don't cause such irreversible growth. I myself, do not reload 1st fired brass more than 4 times or for a total of 5 reloads. As their diameter grows, that metal has to come from somewhere and where it comes from is often less length length. Usually around 5 reloads, I hit the 1.685 length or .5015 diameter threshold which lands them in the "charity" peanut butter jar. I know bolt action enthusiasts don't have the same issues as the AR platform in this caliber.

Hoot

EDIT: Don't ever trim 450b cases.
In Theory, there is no difference between theory and practice. In Practice, there is.
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Re: Barnes 200gr XPB and 275gr TSX

Postby mcb » Tue Jul 25, 2017 8:30 pm

Those where measured as fired. I have not resized them yet. I will measure their length and resize them and measure them again.

ETA:

The five cases fired with the 39 gr load:

Fired: .5000 1.688 Sized: .5000 1.691 Change .0000 .0030
Fired: .5000 1.690 Sized: .5000 1.694 Change .0000 .0040
Fired: .5005 1.692 Sized: .5050 1.696 Change .0000 .0040
Fired: .5010 1.687 Sized: .5010 1.689 Change .0000 .0020
Fired: .5010 1.691 Sized: .5010 1.692 Change .0000 .0010

I found it interesting the diameter at just above the extractor did not change.
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Re: Barnes 200gr XPB and 275gr TSX

Postby Hoot » Wed Jul 26, 2017 8:21 am

mcb wrote:Those where measured as fired. I have not resized them yet. I will measure their length and resize them and measure them again.

ETA:

The five cases fired with the 39 gr load:

Fired: .5000 1.688 Sized: .5000 1.691 Change .0000 .0030
Fired: .5000 1.690 Sized: .5000 1.694 Change .0000 .0040
Fired: .5005 1.692 Sized: .5050 1.696 Change .0000 .0040
Fired: .5010 1.687 Sized: .5010 1.689 Change .0000 .0020
Fired: .5010 1.691 Sized: .5010 1.692 Change .0000 .0010

I found it interesting the diameter at just above the extractor did not change.


That's the heartbreak of Case Head Growth. One thing I did, was customize one of my RCBS #3 shell holders by milling off some of its height in the interest of sizing further down the case. Kinda akin to the effect that AR Small Base sets have. It'll buy you back a little diameter, but it's not a miracle worker.

Hoot
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