.45 cal mini Minié

[Diogenes415]

For decades I've shot mostly .50 cal BP rifles (1:66 to 1:28 twists), stick with and learn about one thing inside and out, but recently got a .45 cal to save on lead when just plinking at the range and hey, .45 is a popular BP match caliber anyway, right? I was new to .45 cal and ran out of what little extra/odd .440 RB I had left accumulating over the decades and decided to try the .450 conicals I cast and use in my revolvers. My .45 cal rifle is an old Jukar from the 70s with about a 1:66 twist so I knew that the conicals would exit the muzzle but not quite in the direction I'd really intended. So I got to thinking, in the mid 1800s a brilliant guy named Claude-Étienne Minié had the idea of making a conical bullet to be used in the slow twist .58 caliber rifles of that era that had a hollowed base... one that would flare to engage the rifling of the barrel and was somewhat nose heavy to act like a badminton birdie and fly fairly true despite the slow rifling twist (Lee 12 ga slug molds anyone?). So I chocked up several .450 conicals in my lathe and began to hollow out the bases. Now all of this is still trial and error as to the profile, width and depth of the cavity but so far they've all been an improvement over the solid .450 conicals.

Does anyone here have any insight or can direct me towards info concerning making mini Minié's to save on lead and time I may spend on experimentation?

https://www.flickr.com/photos/diogenes415/21225953424

 

[kBob]

As you seem to have some machining experience why not just make up piece the shape of your preferred hollow base and stick it on a center pin you can clamp in your existing die, via a hole in its closed base?

Take a look at some Minie dies for the .58s or .577s. Some have such a piece attached to the die and others simply a removable bit on a pin with a wooden handle to protect one from the heat.

I googled "Minie Ball Dies" and got several images of what I am taking about.

BTW how much does you modified .450 bullet weigh? What loads have you used with it? What sort of accuracy are you getting?

-kBob

 

[Diogenes415]

The mold I'm using has the sprue at the base so there isn't much room to work with for mods as it is. I thought about eventually casting a mold like the RCBS Minie mold but in aluminum once I decide on cavity specs but for now I'm working on a jig to mount on my drill press in which I merely drop a conical into a recess and plunge a custom profile spade bit to a predetermined depth. That seems to be the easiest and quickest solution so far.

The conicals are about 200gr to start with but have varied from ~155-~175gr once modified depending on the cavity size. On average groups were moderately improved at 50yds but considerably better at 100yds. Powder charges varied from 45gr to 75gr. It's all still experimental and I have a lot more data to obtain.

 

[PapaG]

Couple of hints. Don't make the skirts too thin or they'll blow out and kill you accuracy. I made up a minie mold years ago and had to redo the base pin as the skirts blew out even with moderate loads (recovered in snow). Second, pure lead, as you are undoubtedly aware is essential to obturation.
I took some 50 cal maxi balls way back and hollowed the bases out but didn't see any appreciable improvement over the un-minie'd version. The old Lyman 450229 (think that is the right number...mold is downstairs and I'm up) only weighs about 155 grains and worked for me in several "round ball" twist rifles. Each is a law unto itself. 45 Maxis worked in a 1 in 66 douglas barrel with 100 grains of FFg also.

 

[Diogenes415]

Thanks for the info PapaG.... that is awesome! Maybe I'll order a couple of different maxi molds when I finally order a round ball mold... after all, I was just using what I had on hand and wondering if I could make it work. Maybe this is a rabbit hole not worth going down.

*Edit
I just saw that TOTW has a Lee Modified Minie mold in .450... I didn't know that existed.