1000th thread in General Discussions

[Ian]

Somebody had to do it.....

Anyway, I was thinking about pressure peaks and curves this afternoon while grinding a hss lathe tool and that lead to thinking about bullet bases riveting in revolver forcing cones, and suddenly I realized that pressure peak and location may be why .45 ACP convertible cylinders tend to shoot better than the .45 Colt cylinders in SAA revolvers.

Typically, the pressure will peak right about the time the bullet base clears the case mouth. Now, if the bullet is in the relatively unsupported area of cylinder throat, gap, and forcing cone when pressure peaks, doesn't it stand to reason that there would be less bullet upset if that peak occurred while the bullet was sliding through a long, straight cylinder throat instead? Less upset = better accuracy most of the time, so maybe that's it.

I know it's counter-intuitive that a bullet could shoot better even if it hits the rifling at nearly full speed, but the infamous Paradox revolvers were reported to be very accurate and they represent an extreme of bullet speed and sudden encounter with rifling twist. Anyway, there may be something to the long cylinder and bullet upset may be more of a problem than skid.

 

[Brad]

Makes sense.
I will also propose that maybe the 45 ACP cha,bears are cut to a reasonable size while the 45 Colt chambers are cut with an old 500S&W reamer or something close.
Not saying Roger 45 Colt chambers are big but they will accept brass fired in my 1894 Marlin and it has a huge chamber.

 

[Ian]

I wish all my .45 Colt revolvers had cylinders bored like my Open Top because even carbide-sized cases barely wiggle in the chambers.

 

[Brad]

Oh, mine wiggle plenty.
When I have a case failure the split is 80%the length of the case. Pretty dramatic actually.

 

[Ian]

I have a Ruger too, with chambers that also meet that description.

 

[Pistolero]

Hmm. I haven't noticed any particular oversized on my .45 Colt chambers, but I
do use old steel RCBS dies, carefully located to NOT oversize the .45 Colt brass
and pretend that it is a straight case when it is actually a few thousandths tapered.

I should put gauge pins into the cyl and see what will go all the way to the chamber
mouth, and what will just start in the back.

Bill

 

[RBHarter]

My ACP is a nice even .453 +.005 while the Colts cylinder was throated with 3-4 different reamers from .452-4546 . They're all .454 except the fat one now , which throws out of the 3" 50 yd to make it a 5" group . I haven't shot the ACP cylinder much but it's as good as the 1917 which is pretty good with 200-230 gr cast which shoot to the same place as the 230 ball .

 

[waco]

This one caught my eye. I have been looking at a Blackhawk Bisley in .45 Colt/45ACP
Lipsey has a slick looking one that is stainless with laminate grips and a 3 3/4" barrel.