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wayne r
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Win. low wall
Feb 1st, 2010 at 7:25pm
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To all,
What is the safe working pressure on a low wall in 25-20, have some
info with pressures! These old guns are real steep learning curve!
   Thank You all,   Wayne r
  
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waterman
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Re: Win. low wall
Reply #1 - Feb 3rd, 2010 at 11:39am
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Are you referring to the 25-20 Single Shot or the 25-20 WCF (repeater)?

From Phil Sharpe's Complete Guide to Handloading (1937):

25-20 Single Shot:  86 grain lead bullet & #2400 powder.

7.0 grains 2400 gives 1130 fps.  Pressure too low to measure.
8.0 grains 2400 gives 1570 fps, pressure 19,900 psi.
9.0 grains 2400 gives 1700 fps, pressure 25,000 psi.
10.8 grains 2400 gives 1990 fps, pressure 40,000 psi.

4.8 grains Unique & 86 grain lead bullet gives 1480 fps, pressure 20,000 psi.
5.0 grains Unique & 86 grain lead bullet blows primers in my Stevens 47/44 rifle.

25-20 Repeater: 86 grain lead bullet

5.0 grains 2400 gives 1020 fps, pressure too low to measure.
6.5 grains 2400 gives 1300 fps, pressure 13,600 psi.
9.2 grains 2400 gives 1765 fps, pressure 25,000 psi.

3.0 grains Unique gives 1095 fps, pressure 11,200 psi.
4.8 grains Unique gives 1485 fps, pressure 20,000 psi.
5.0 grains Unique & 86 grain lead bullet blows primers in my Low Wall.
  
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waterman
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Re: Win. low wall
Reply #2 - Feb 3rd, 2010 at 1:34pm
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I played around with Sharpe's data for 2400 powder in an Excel spreadsheet.  I wish Sharpe had jammed in enough powder to generate 40,000 psi in the 25-20 WCF case.  There are just not enough data to do a better analysis.

I also wish I could figure out how to display the graphics here.

The Excel curve fitting routine gives the following, where Y = pressure, psi and X = MV:

WCF case; Y = 0.0071 X^2.0163

SS case; Y = 8E-06 X ^2.9382

My interpretation is that the WCF case requires more pressure to achieve the same velocity.  Sharpe said "the (WCF) case has a sharp bottleneck, thus creating high pressures without achieving reasonable results". 


  
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wayne r
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Re: Win. low wall
Reply #3 - Feb 3rd, 2010 at 3:15pm
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   Waterman,
  Thank you for your reply, guess I did not give enough info on first post!I have a low wall 25-20 repeater,am shooting 7.5 gr.2400
90 gr.lead bullet. Did not know if I could safely increase charge. I do not want to run "hot " loads! The action is pretty tight and want to keep it that way.Serial no. is 50,000 + well used, barrel has been relined and shoots better than my 62 year old eyes can. If ran at mid twenties for pressure,will I stress the action!
        Thanks Wayne r
  
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waterman
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Re: Win. low wall
Reply #4 - Feb 3rd, 2010 at 8:29pm
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Wayne,

My GUESS is that (with a lead 90 grain bullet), your 7.5 grains of 2400 is pushing about 1450 fps and the load is generating about 18,000 psi.

If your Low Wall in 25-20 Repeater is anything like mine, it is very sensitive to case length (critical!), bullet seating depth, bullet alloy, lube recipe, & make of primer as well as powder charge.  You may also wish to try breech seating. You need to keep a notebook and write down everything you try.

With everything else equal, I think you ought not to try to go beyond about 1550 fps (not much over 8.0 grains) until you have tinkered with the rest of the variables.

I think you will find that getting the Repeater cartridge to shoot well is about the most sensitive or difficult of all the conventional single shot cartridges.

I tried all the sorta old timey (pre-1940) smokeless powders (Unique, 2400, 4227, 4198 & SR 4759) with mine and 2400 seems to do about the best.  But you have to tinker with all that to get the blasted rifle to shoot tight little groups, if it is indeed possible.  I do not have the correct recipe for mine.


waterman
  
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