[Smokewagon]

Does anyone here have any experience, in using large magnum pistol primers, in BP substitute cartridges? Namely Triple 7, in .45 Colt.

I'm leary to give it a try, but I do have a lot of magnum primers. Gee, I'm curious, but won't try it unless I'm certain it's safe.

 

[unclenick]

No experience, but I expect the same result as when using other smokeless powders. You should knock the charge down 5% and work it back up. A good primer on primers is here.

A chronograph is a good tool to have for the above. As you reduce a charge, it is a rough rule of thumb that the chamber pressure will be constant if the velocity drops as the square root of the ratio of the difference in charges. So, if you put in a hotter primer and reduced the charge 5%, the ratio of the charges is then 0.95, and the square root of 0.95 is about 0.975, so you should find your new average muzzle velocity is 0.975 times that of the original velocity if the new primer was hot enough to keep the peak pressure the same as with the original charge.

If the velocity were higher, you'd want to reduce even more. If you want to, go down 10%. The peak pressure with the original primer will then be about 20% lower. Work up with the new primer.

To make this a little easier, I'll put a constant pressure table below, based on the above formula. Let's suppose your original velocity was 2000 fps, then:

 New    Expected   Constant
Charge     MV     pressure V
100.0%   100.0%    2000 fps
 99.0%    99.5%    1990 fps
 98.0%    99.0%    1980 fps
 97.0%    98.5%    1970 fps
 96.0%    98.0%    1960 fps
 95.0%    97.5%    1949 fps
 94.0%    97.0%    1939 fps
 93.0%    96.4%    1929 fps
 92.0%    95.9%    1918 fps
 91.0%    95.4%    1908 fps
 90.0%    94.9%    1897 fps

 

[Smokewagon]

Thanks! Probably not that much of an issue in an old model Vaquero then.

 

[Bigfoot]

Do a google search. I seem to recall that 777 had some pressure spike issues in cartridges. I may be wrong, never used it , just recall something about it in cartridges. You are probably ok using blackpowder techniques loading 777.

Don

 

[MikeG]

Thanks! Probably not that much of an issue in an old model Vaquero then.

Nah. I run Ruger-level .45 Colts through my Vaquero; not many but it doesn't seem to hurt it. I don't know how much pressure you could get with Triple-7, but it seems unlikely to get to magnum hangun levels....

 

[Levergunz]

I have used full case charges of 777 in my 45's before ,but always used std primers.I dont think a Mag primer would make much difference.I have since switched the 45's to 2F blackpowder with cut loads(20 gr 2f and the rest corn meal or case cleaning media).It makes no difference with the Blackpowder which primers I use.If you cut the charge remember to add a filler to take up the space in the case.The 2f has given me better accuracy.