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Author Topic: 45 Colt BC barrel vs. 44 Mag barrel on SB1 frame, check my math  (Read 959 times)

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Offline Doublebass73

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45 Colt BC barrel vs. 44 Mag barrel on SB1 frame, check my math
« on: January 30, 2011, 05:08:19 PM »
A recent thread about the .357 Max on an SB1 frame got me thinking about comparing the .45 Colt Carbine barrel with published Ruger-T/C loads to the .44 Mag on an SB1 frame. H&R fits the .44 Mag barrel to the SB1 frame so that's obviously safe but they never fit the .45 Colt Carbine barrel to the SB1 frame before they discontinued it. I did a breech force comparison of each round at max pressure. I kept pressure units in CUP for apples to apples. I used 40KCUP for the .44 Mag (correct me if this is wrong) and 30KCUP for the .45 Colt which I took from Hodgdon's Ruger-T/C data section for the .45 Colt. Here's the math for each using breech force = pressure x case head area (A = Pi X r^2):

Case head diameters & radii:
.44 Mag - 0.457" radius = 0.2285"
.45 Colt - 0.480" radius = 0.240"

Case head area:
.44 Mag - 3.14 * 0.2285^2 = 0.164 square inches
.45 Colt - 3.14 * 0.240^2 = 0.181 square inches

Max Pressure:
.44 Mag - 40KCUP
.45 Colt - 30KCUP

Breech force:
.44 Mag - 40000 * 0.164 = 6560
.45 Colt - 30000 * 0.181 = 5430

It appears as though the .45 Colt BC barrel with published Ruger-T/C loads exerts less force than the .44 Mag on an SB1 frame, opinions?







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Offline Spanky

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Re: 45 Colt BC barrel vs. 44 Mag barrel on SB1 frame, check my math
« Reply #1 on: January 30, 2011, 06:00:51 PM »
I think the only thing that stopped them from putting it on the shotgun frame was the fact that guys could easily rechamber them to 454 or 460 and blow the gun (and themselves) up in the process.
If you've got a good shotgun frame and a 45LC barrel that fits it go for it. You've already done your homework and crunched the numbers to show that it's well under 44mag pressures. ;)



Spanky
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Offline quickdtoo

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Re: 45 Colt BC barrel vs. 44 Mag barrel on SB1 frame, check my math
« Reply #2 on: January 30, 2011, 06:36:06 PM »
What Spanky said.  ;)

Tim
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Offline petemi

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Re: 45 Colt BC barrel vs. 44 Mag barrel on SB1 frame, check my math
« Reply #3 on: January 31, 2011, 02:48:26 AM »
That is all sound logic,  but what would happen if you took a SB1 .44 Mag and blew it out to .445??  Would it blow up?  If so, there's really no reason not to put the .45 on a SB1 frame.  One would be as hazardous as the other.  I don't know, just asking.  I don't put any centerfires on SB1 frames except muzzleloaders and shotguns.......It's just against my religion.

Pete

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Offline Doublebass73

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Re: 45 Colt BC barrel vs. 44 Mag barrel on SB1 frame, check my math
« Reply #4 on: January 31, 2011, 03:36:35 AM »
What's the max pressure for a .445 super mag? Maybe it falls within what H&R considers safe for an SB1 frame where a .454 would not?
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Offline quickdtoo

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Re: 45 Colt BC barrel vs. 44 Mag barrel on SB1 frame, check my math
« Reply #5 on: January 31, 2011, 05:23:19 AM »
The 445 isn't a SAAMI cartridge, but the data goes to about 43kcup compared to 40kcup for the 44mag.

Tim
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Offline Doublebass73

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Re: 45 Colt BC barrel vs. 44 Mag barrel on SB1 frame, check my math
« Reply #6 on: January 31, 2011, 01:52:11 PM »
Quote from: quickdtoo on January 31, 2011, 05:23:19 AM
The 445 isn't a SAAMI cartridge, but the data goes to about 43kcup compared to 40kcup for the 44mag.

Tim

We don't know what H&R officially rates the SB1 at for breech thrust but the 445 isn't much higher than the 44 Mag which might explain why they put the 44 Mag on an SB1 but not a .45 Colt. The 454 Casull is somewhere around 55KCUP which would probably destroy an SB1 in short order.
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