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shermo
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25 21 pressure/ thrust
Oct 13th, 2025 at 4:15pm
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Humbly admitting my lack of knowledge here, years back bought a No2 ballard was made into a 38 55,had been shot quite a bit but not by me. Bought a new douglas 1 in 12   .25 cal barrel had it put together by a qualified fellow an had it chambered in 25 21 because to me the combination of small base and a long straight case seemed logical( plenty of hoop strength and not a great deal of breech thrust) my question is I wanted to breech seat with 7.5of 4227 using a hoch tapered that drops 108 gr 30 to 1 . Forgot to mention breech block has been modified to a small diameter firing pin. Wondering if someone with quick - load could look at the numbers  , or ought I stick with my current load of 6.5 of 2400 and the standard Lyman bullet. Thank you
  
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Dellet
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Re: 25 21 pressure/ thrust
Reply #1 - Oct 13th, 2025 at 10:03pm
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All of this is just a basic thumbnail, I used my cartridge and rifle specs, 28” barrel, 117 grain bullet, .020” ahead of the case. 

The black powder estimates came from here. Same cartridge and rifle data, using Swiss 2 and 3F powders. 
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Most thrust calculators use internal case diameter, I included both internal .280” and case head diameter .376”

4227 7.5 grains
9,000 psi
1225 fps
558# internal
1000# case head

2400 6.5 grains
12,000 psi
1350 fps
744# internal
1332# case head

2f Swiss 21 grains
16,000 psi
1325 fps
992# internal
1700# case head

3F Swiss 21 grains
21,0000 psi
1410 fps
1300# internal
2300# case head.

If the velocities are close, you can probably trust the pressures. Hope that helps some

Link to black powder pressure added
« Last Edit: Oct 14th, 2025 at 5:36am by Dellet »  
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shermo
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Re: 25 21 pressure/ thrust
Reply #2 - Oct 14th, 2025 at 5:07am
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Thank you sir
  
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bohemianway
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Re: 25 21 pressure/ thrust
Reply #3 - Oct 24th, 2025 at 9:40am
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Years ago I was using 9 gr 4227 in the 25-21 on a 44 action at about 1,400 fps and it kept bending the breech block pivot after several rounds so I stopped.
YRMV,
Charles
  
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