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Discussion Starter · #1 ·
GP100, 6".
what would be considered max cup pressure?

I see pressures from 20k to 40+ and do not want to get too high. Mainly used for target. Thinking of 158 gr bullet.

I carry 180 gr for deer hunting...factory loads.

Appreciate the input.
 

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drmajor, As Terry_p stated ... 357 Mag max pressure is now 35k psi. Before the change to psi testing with piezo transducers, the old standard for "crusher method" testing was rated in CUP. In 1995, two things happened at about the same time .... SAAMI lowered the pressure standards for 357 Mags and started rating pressure in psi. If you have an old reloading manual or if you use old load data from Internet sources, you may still see pressures stated in CUP. CUP and psi are not interchangeable. If you plan to reload 357 Mags, I would highly recommend buying a current reloading manual such as Speer #14 or Hornady 8th Ed. All their 357 Mag loads are tested under the current "35k psi" standards.
 

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Discussion Starter · #4 ·
I was looking at the Hodgen sight data where it still list CUP. for instance:

158 GR. CAST LSWC Hodgdon Universal .358" 1.610" 4.0 890 15,700 CUP 6.2 1247 33,400 CUP
158 GR. CAST LSWC Hodgdon HP-38 .358" 1.610" 3.4 796 12,600 CUP 5.0 1109 23,900 CUP
 

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Mainly used for target.
In that case I wouldn't worry to much about the high end. For targets, I like my 158g SWC zipping along between 1000-1100 fps. No where near the top end.

If I remember right 40K CUP was max, now it is 35K PSI as stated above. So when you see 33K CUP or 24K CUP, they are well within safe loads for .357 even if loading at 'old' data manuals....

As far as I know, no one blew up guns using the data in the 'old' manuals. data was good then, still is good now unless there is a formula change.... Just check against multiple references... The procedure still remains the same regardless : 'Work UP' your loads if looking for max loads! . With lead bullets you may be backing off anyway to prevent excessive leading.
 

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rclark, The old SAAMI standard for 357 Mag was 46,000 CUP, which converts to 43,500 psi. SAAMI reduced the max pressure by about 25% (from 43.5k psi to 35k psi), which is quite a bit. The old SAAMI pressure standard did indeed ruin some guns ... maybe not Rugers but it did take out a good many S&Ws. The standards were lowered to make all 357 Mag guns last longer. Pressure and velocity do not track linearly so the 25% reduction in pressure only lowers velocity by about 10%. SAAMI did the same thing at the same time with 44 Mag pressures but only lowered them by 10%.
 

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And just for giggles - CUP or PSI doesn't always equal higher velocity. Look at the low CUP's for 'lil gun powder vs. H110 - yet velocity is right there. At least for 158gr and 180gr. I have no load data for under 158gr with 'lil gun.
 

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And just for giggles - CUP or PSI doesn't always equal higher velocity. Look at the low CUP's for 'lil gun powder vs. H110 - yet velocity is right there. At least for 158gr and 180gr. I have no load data for under 158gr with 'lil gun.
And according to Hodgdon, those pressures/velocities are out of a 10" test barrel...

I suspect Lil'Gun needs that length to 'get up to speed', where H110 can get more velocity in shorter barrels...
 

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rclark, The old SAAMI standard for 357 Mag was 46,000 CUP, which converts to 43,500 psi. SAAMI reduced the max pressure by about 25% (from 43.5k psi to 35k psi), which is quite a bit. The old SAAMI pressure standard did indeed ruin some guns ... maybe not Rugers but it did take out a good many S&Ws. .
Iowegan, I've been looking for that number for a while.

I have a .357BH, and I know it will last longer than I will. I also suspect it will easily handle loads I wouldn't want to feed my 77/357. But those higher pressures would be pretty hard on the J Frame Smiths, or many other light frame CW designs.
 

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When SAAMI gutted the pressure standards for the .357 Mag in deference to manufacturers of medium frame magnums, it immediately made me wish I'd bought a RedHawk in .357. I'm fairly certain that one of THOSE revolvers wouldn't shoot loose with magnum ammo of EITHER vintage.
 

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wouldn't shoot loose with magnum ammo of EITHER vintage.
Nor would a Blackhawk ... which you can still buy today. But, really, if you are wanting that much power to be pushing edge of .357.... go up in caliber.... and if that isn't enough go up in caliber again!
 

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I shoulda been more specific. I'd like a double action revolver in which I could approximate the original ballistics of the .357 Magnum round without beating it apart. I guess a S&W M28 would work, but I suspect that a .357 Redhawk would be more sturdy.

CLARK, you are absolutely right about going to a larger caliber for more power, abd it's one of the reasons I own a RedHawk in .45 Colt. Getting the original specs out of the .357 was what I was waxing nostalgic about.
 
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