.40 Minie Design

[nkbj]

If you were to design a .40 caliber minie for GM rifling and their standard 48" twist what would you make it look like?

 

[Eric Krewson]

I have a friend who shoots .40 175 gr pistol bullets patched with butter paper out of his GM barrel, He gets 1 1 /2" groups at 50 yards and has killed a bunch of deer with that load.

 

[BlackHillsBob]

whats butter paper? ive use 9 pound paper and 18 pound paper single wrap but dont know what butter paper is?

 

[45man]

I would not make a hollow base bullet. I would look at the Maxi Ball design. Just get a good fit.

 

[Grenadier1758]

Use the paper that is used to wrap a stick of butter. (?)

You need to eating a lot of butter to get enough paper to wrap a large quantity of bullets.

 

[BlackHillsBob]

thats interesting, tell him number 9 paper dry wrapped works also. thanks

 

[Eric Krewson]

My friend says there is a layer of plastic on butter paper that needs to be pulled off but comes of easily. I am not sure exactly what caliber pistol bullets he is using but have a few in my shop I can measure. It is raining right now and I don't want to walk to the shop but will check later.

 

[BrownBear]

I would not make a hollow base bullet. I would look at the Maxi Ball design. Just get a good fit.

Agreed. GM rifling is deep compared to that of rifles intended for shooting minies.

"Twas me seeking proper diameter I'd use a modern pistol bullet and "cheap out" by buying a .395" or so collet and punch for my RCBS Lubrisizer. I doubt there'd be any penalty in a muzzleloader for "over-squishing" a 40 cal bullet passing through it.

 

[rafterob]

Butter paper is kinda like butcher paper. Usually white (that's all I've seen) That's what is used to wrap bulk butter in (the few places that still make and or sell it in bulk).

 

[nkbj]

I'm thinking that for a .40 caliber minie to fit GM rifling something about like the Ideal #386378 but with a little more pointy nose would work well.
The two GM forties I've worked with both have had .403 bore diameters.

 

[EC121]

Do a search for ".40 cal. wadcutter bullet".

 

[nhmoose]

Here's a drawing of a 40 cal REAL bullet

 

[Loyalist Dave]

I would have a mold made to make that ^^^^.
The Rifling Engraved At Loading bullet in a forty requires very little swaging to get it onto the rifling, as compared to much larger calibers.

LD

 

[Eterry]

I just cast a cpl hundred 40 cal REAL's from a custom mold.
I think they'll do well on deer and rooters... they weigh 197 grs, iirc.
I plan on listing some over on classifieds.

 

[nkbj]

I've used various .41 caliber bullets sized to make the rear end fit the bore and the front end engrave on the rifling. The GM barrels 48" twist was too slow to give consistent results. That's because of needing inertia to get the flat base to expand. More inertia means longer bullet and longer needs faster twist. I'd have a group forming up at fifty yards but then see tippers making slightly oval holes in the target. Hence the interest in a hollow base, in other words a minie not a maxie or REAL.

About the technique developed to size bullets on the rear and leave the front large...
I do that to shoot various .41 caliber molds in my .41 caliber 1858 Remington. I size them the same way to make the rear ends slip into the chambers and shear on the front like a round ball. Having a barrel with rifling to use the same "REAL" type slugs is tempting but I'm not willing to pony up the funds.

Some .41 molds...

 

[nkbj]

These are from a .40 hollow base adjustable length (could make them shorter) but the diameter is a little small for the GM .403 bore.

 

[nkbj]

These were fired from a 38" long GM forty with the .403" bore.
They stabilized but required too heavy of a charge. Could use a pin that doesn't reduce in diameter to make the skirt a little thinner.

 

[Eterry]

Here's a drawing of a 40 cal REAL bullet
View attachment 9703

That looks pretty much like my 40 cal REAL conicals.

I've listed them in the classifieds.

 

[nkbj]

Did some testing this weekend to see how much powder it took to seal off the deep rifling in the .40 GM drop-in.

 

[nkbj]

What I've gone with is the Ideal/Lyman #386178 hollow base with a barrel machined to work with that mold and others.
But I'm gonna continue to work with the hollow bases in the GM forty.