Sizing conicals to bore on .50 muzzleloader

[LaneP]

I recently got a Pedersoli Lyman Great Plains Hunter in .50 cal. These come with a fast 1:24" twist. I haven't had much range time with it due to the weather, but come the spring I expect to get alot of lead downrange.

The Pedersoli GPH .50 stated specs are .500" bore and .512" groove. I verified that by taking a Hornady GP lead HP bullet, tapping it partway into the muzzle, removing and measuring. The base portion I tapped in the bore measures exactly .500" on my calipers. That bullet is a very tight fit in the bore.

I can grab an Arsenal Molds .504" TC style bullet mold (365 gr), but they also offer custom diameters as well. My thoughts were to go down to .502" for this barrel in order to make field loading easier on a second or third shot.



Thoughts? I am hoping a .502" will obturate sufficiently, provide sufficient resistance to gas but not require being hammered in the bore. But if you have experience that varies from this thought, please let me know.

 

[hawg]

I would try to find a few bullets in the diameter you want before I spent money on a custom mold that might not work.

 

[LaneP]

100% right on that. The industry standard for commercial shelf .50 conicals seems to be about .504", which are way tight in this bore. Okay for a range bench when I can swab fouling and use a range rod, but for the field I see that being a major issue.

One scheme I was considering was getting a .501" Lee push sizer, order the mold to drop at .502", then if need be I can knurl them up to .503", possibly even .504". Within the range of .501" - .504" I should find my happy place (in theory).

 

[243winxb]

The original T/C maxi- ball is not the same diameter, from top to bottom. The larger top band is made to engauge the rifling on loading. The bottom can ride on top of the lands. On firing, the base/botton will expand to the groove diameter, if using pure lead & enough powder.



Note. I only have T/C in 45, so diameters of the 50 may need adjustment?

 

[LaneP]

The original T/C maxi- ball is not the same diameter, from top to bottom. The larger top band is made to engauge the rifling on loading. The bottom can ride on top of the lands. On firing, the base/botton will expand to the groove diameter, if using pure lead & enough powder.

View attachment 1046875

Note. I only have T/C in 45, so diameters of the 50 may need adjustment?

Thanks for that info, I just emailed Arsenal to ask if their .504" mold driving bands differ in diameter or all are same. Big help narrowing down a solution.

 

[hawg]

The original T/C maxi- ball is not the same diameter, from top to bottom. The larger top band is made to engauge the rifling on loading. The bottom can ride on top of the lands. On firing, the base/botton will expand to the groove diameter, if using pure lead & enough powder.

View attachment 1046875

Note. I only have T/C in 45, so diameters of the 50 may need adjustment?

I used those in a .50 Hawken. They fit snug until you get to the top band. It takes a hard smack on a short starter to get them started and the full length of the short starter before you can use the ramrod. At least that's how it was with mine. YMMV.