Confusion Abounds
Chamber casting length * original cartridge COL size * Bullet diameter * New custom configured case
Since I started this project of reloading some rounds for the M1871 Army Rolling block pistol I have found most all information to be not only confusing and convoluted, but in some case contradictory.
The start of this thread the OP states that he can chamber a 50-70 round or perhaps just a case in his pistol. In my pistol this is not the situation. As seen in my photos I can not chamber a full size 50-70 case and the same is true for a carbine length (1.35") case. Comparing a full size 50-70 case to the chamber casting it is apparent that the full size case is too long for the chamber. So, I am not sure what is going on with the Op's pistol chamber.
I made a chamber casting of the M1897 I have and compared the results to an original .50 Rem cartridge.
original factory round. I cut down 50-70 brass to more correct length where the bullet would be much closer to engaging the rifling.
Conflicting information regarding the correct bullet diameter. Some information I have come across states the correct size should be anywhere between .502 to .514 Depending on which article you read.
I slugged my bbl and took some measurements also measured the casting I made. Difficult to do because of the 3 groove rifling. The best "guesstimate" for my pistol comes out to be about .5094. Some writers claim to be able to use bullets straight from a mold casting a diameter of .514. I seen other articles claim the correct mold would cast a .508 bullet. Yet another source offers a bullet dia of .502.
Now here's the kicker...... measuring the bullet in the original cartridge, the diameter is somewhere around .506. But that is reading a 100+ year old bullet still seated in it's case.
I'm pretty sure I have the correct case length figured out. Just not sure on what bullet diameter I should consider, On one hand for my bore, the.514 seems a bit to large and the .502 seems too small. I'm not certain on just how much over size I can get safely by with. From all I've ever learned regarding the correct diameter it should be around .002 or .004 over groove diameter.