ROA bore diameter?


January 23, 2011, 04:31 PM
I am not real good at measuring bore diameters. I have tried slugging bores but distrust my results.

Those of you who are better at this than I am, what is the groove diameter on a Ruger Old Army? Does it vary any from the early production models to the later, fixed sight versions?

The question arises because I want to use the best diameter bullet possible in a Kirst Converter, and also I am considering loading .45 Colt cases with round lead balls as an experiment because winter is long and boring.

Thanks for any enlightenment you can provide.

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January 23, 2011, 04:48 PM
The grooves on all 4 of my Old Armies measure 0.451 inches.

January 23, 2011, 05:31 PM
the data i have for loading my colt 45 cases says to use the .454 ball

January 23, 2011, 05:37 PM
Thanks for the quick response, particularly since the Bears just scored for the first time in the game!

Which of your references lists round ball cartridge loads?

January 23, 2011, 06:47 PM
Its a lyman bullet listing found in The Complete Reloading Manual for the 45 colt which i purchased through midway.

It does not list BP but i have used BP loading practice with the same ball
with good results in my pietta 58.

it does not like to work in lever actions though because its a little to short

January 24, 2011, 01:43 AM
your r o a manual says use .454 conicals and .457 balls for best results, hornady .454 cowboy frontier bullets work very well,both in the r o a and cartridge models,try it youll like it:D also the kirst konverter 45 cal is designed for .454 lead bullets,

January 24, 2011, 11:53 AM
Let's reverse engineer this. If the book say 454s then the bore will be that or 1-2 thousands smaller leaving you in the vicinity of 452. I'd bet on 451-452.

I can't seem to get a consistent slug measure either. I always clamp the caliper down hard enough to cause the soft lead to deform.

January 24, 2011, 05:35 PM
It seems that .451-2 is what I have. Bullets sized at .454 and balls fired at .457 work well. I also have an oversize cylinder that throws .456-7. It all works but I can get leading with the over-sized bullets that I never experienced in smaller diameter.

The larger diameter loads used the same pure lead bullet, RB and lubricant. I think I can mitigate the the leading and accuracy problems by messing with the loads and lubricants.

January 24, 2011, 06:36 PM
Groove diameter of 0.451. I use 0.452 bullets when reloading Colt 45 for use with my conversion cylinder.

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