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Old October 15, 2018, 06:49 PM   #1
mehavey
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38-55 HiWall -- Heavy bullets -- Black Powder

For those who think 18:1 is too slow for BP

325gr/Accurate Molds (another one ordered on Saturday/Arrived in Thursday/Cast on Friday/Shot on Saturday)


Last edited by mehavey; October 15, 2018 at 06:58 PM.
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Old October 15, 2018, 06:51 PM   #2
Unclenick
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Nice group! How long is that bullet?
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Old October 15, 2018, 07:00 PM   #3
mehavey
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1.18"


post: I lied.
QL predicted 1,155fps from an earlier/lower trial from which I'd tweaked the Miller K-factor for Swiss 1.5
LABRADAR showed actual to be 1,159fps
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Old October 15, 2018, 07:44 PM   #4
Unclenick
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Stability factor of over 1.7. High end of optimal, so stability should be just fine and looks like it is!
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Old October 16, 2018, 08:37 AM   #5
the Black Spot
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Nice!
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Old October 16, 2018, 02:21 PM   #6
T. O'Heir
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The twist is about the bullet weight. Not the propellant. 1 in 18 is apparently common for the .38-55 though. Who told you it wasn't?
Mind you, the BP cartridge guys argue about twists too.
http://www.bpcr.net/forum/viewtopic.php?t=2369
https://www.assra.com/cgi-bin/yabb/Y...num=1202346186
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Old October 16, 2018, 05:27 PM   #7
mehavey
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Quote:
The twist is about the bullet weight. Not the propellant
Bullet Weight --> ~ length
Black Powder --> ~ speed

Miller's is all about length/diameter and speed re twist.

I one looks at "The Internet" one finds all sorts of opinions as to 38-55 heavy weight reqm'ts and performance... ranging from 12:1, 14:1, 18:1 ... and all sorts of "that's too slow a twist" for BP speeds. In fact, straight Greenhill's likes a 14 twist for those lengths/diameters/speeds Still, things are a bit more complex that straight Greenhill.

So like UncleNick, I went to both JBM & Berger w/ real data on real bullet and real lower-bound speeds and plugged it in for an 18 twist:



. . . and it appears that theory and actual shooting data do overlap.


.

Last edited by mehavey; October 16, 2018 at 10:10 PM.
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Old October 16, 2018, 06:32 PM   #8
Jim Watson
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My .38-55 has a 15 twist by rebore from .32-40.
It does well with the 336 gr Lyman "Mini-Snover."
I load 40.6 gr Swiss 1 1/2 because that gives compression the thickness of the over powder card wad with the top lube groove just covered.

Won't knock down all the 500 metre rams I hit, though.
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