BPCR Rifling Depth

[brasshog]

I slugged my first barrel today and was suprised at the results The cartride is 38-50 Remington Hepburn ( Rem #5 Rolling Block-Smokeless) in a 1 in 14 twist green mountain barrel. I had assumed that it would mike out around .378 but instead it was a true .375 groove with the lands being .3695 . These were measured with a dial caliper since it is what I have. I'm no expert at rifling depth. My question "Is BPCR rifling depth differant for a BP rifle versus a smokless rifle ?". I assume that it would be due to possible fouling issues but don't honestly know. Also, what are your suggestions on proper cast boolit diameter for best results ? Thanks

[EDG]

A lot of people have problems slugging barrels. I would suggest you make several tries especially if you get a diameter that is smaller than expected. Calipers are really not the tool of choice either. They have about 1/10 the resolution of a micrometer.

[brasshog]

I agree that a micrometer is better for this but atm I do not own one. I took a large round ball and drove it through using a wooden dowel rod. Again, I'm new to this. Thanks

[Chill Wills]

Brasshog, I think you did ok measuring the slug. It is about what I would expect (.375"). The minor diameter might be a little harder to measure but it does not make as much difference. You should be looking for a mould that will cast .376" or even .377". It is great if you do not have to reduce a bullet too much to get it to this size.

On the other hand, if the chamber in your rifle is cut with a large (diameter) cylinder, free bore, throat or cut sloppy or what ever... in front of the case, you might find a larger bullet more accurate. This line of logic is "shoot the largest diameter bullet that will chamber".

I think most of the new production barrels from GM, Douglas, Kreiger or Lilja run .375-6". Pedersoli barrels are .380" I have heard.

[brasshog]

The chamber was cut with a Dan Theodore reamer is all that I know atm. I have not purchased the first item as of yet to reload this caliber burt I will soon as I learn more about it. I need to pick up some 30/40 Krag brass first. Does anyone know if there is a differance between BP and smokeless rifling ? Thanks for any info guys.

[littlejack]

If you make yourself a casting of the chamber (either pour, or impact) this will help you determine what size to make your boolits.
Regards
Jack

[country gent]

.376-.377 for groove dia ( bearing section) and a nose dia no bibber than .3685 should work very well. If possible shot as cast and pan lube or finger lube. A Chamber cast would be very helpfull in knowing for sure what the dimensions are of the chamber throat.

[Gunlaker]

I don't think you'll find anything that is black powder specific with regard to the rifling shape or it's depth on that Green Mountain barrel. There are a few people still making barrels specifically for shooting black powder, but those will be low production custom barrels. I know a guy who's made his own and used rifling with rounded corners to reduce fouling issues.

Chris.