New Cap N Ball Bullets

[rodwha]

I contacted Tom at Accurate Molds and asked that he design a light weight .45 cal bullet to use in a cap n ball pistol that the OAL would be roughly that of a ball. This idea cap about after having read someone using a .45 Colt 155-160 grn bullet. The idea that it was roughly the same length, which wouldn't take up any powder capacity, yet have more bearing surface should/would (don't recall if it was theory or observed) increase pressure and velocity.

What he came out with was a 180 grn (WW) bullet .460" OAL.

http://www.accuratemolds.com/bullet_detail.php?bullet=45-180S-D.png

He also designed a lighter bullet and came up with a 160 grn variant.

http://www.accuratemolds.com/bullet_detail.php?bullet=45-160B-D.png

Next will be a heavier bullet ~250 grns in weight with a slightly wider meplat.

I've also asked him to design a light weight bullet for the .36 cal pistols.

What are your thoughts on the 160 and 180 grn bullets working in both the slow twist and faster twist barrels of cap n ball guns? Is there any reason to believe it won't be stable?

 

[BowerR64]

I always thought bullets say in a cartridge has a hollow opening at the bottom. Not just to help the charge push the bullet but as the pressure pushes the bullet it also opens the lips on the bottom of the bullet and expands it a little keeping the seal before it leaves the muzzle.

Does that make any sence?

All of the conical bullets ive see from casts have a flat bottom?

Maybe this doesnt help for black powder?

 

[rodwha]

I know that the rifle conicals of old were under sized so that as fouling built up they could still easily reload. This required a thin skirt (hollow base) that upon firing expanded to seal the bore.

In these pistols it's unnecessary as they aren't undersized.

 

[BowerR64]

What does the ridge in the bullet do?

Is that so you can rub lube around it? or does it help the seal?

 

[rodwha]

It is the lube groove. It helps to keep the fouling softer.

 

[AbitNutz]

I may try a 4 cavity 180. I have a BigLube 150 and 210. My ROA shoots both well.

 

[rodwha]

can you give me the details on what you've done using both bullets? Powder charges used?

I was asked if the light weight bullets would be stabilized in a slow twist repro barrel. I would assume it would as it stabilizes a RB. But does it? You can't detect a keyhole with a ball.

Would they need to be driven somewhat fast? I dunno...

 

[zimmerstutzen]

I suspect the instability arises faster when the length vs width gets nearer to equal. Cap and ball revolvers are not long range elephant guns anyway.

Power in ft lbs is a factor of velocity vs mass. The problem with a cap and ball revolver has always been achieving a maximum ratio between bullet size and powder capacity. I would think, the closer a bullet comes to a geometric cylinder, the better the ratio between bullet mass and powder capacity.

I don't know if anyone has ever done experimenting on the distance that a bullet that is shorter than wide can fly accurately before destabilizing. If such a bullet destabilizes within 25 yards, it may be worthless. If it makes it to 50 yards with sufficiently high velocity, it may be worth it for hunting. If the speeds stay below the speed of sound, I don't know that a flat nose bullet will lose significant velocity by distance intended for it's use.

I like both designs, but might want an even more wad cutter type nose.

 

[Arkansas Paul]

I always thought bullets say in a cartridge has a hollow opening at the bottom. Not just to help the charge push the bullet but as the pressure pushes the bullet it also opens the lips on the bottom of the bullet and expands it a little keeping the seal before it leaves the muzzle.

Does that make any sence?

All of the conical bullets ive see from casts have a flat bottom?

Maybe this doesnt help for black powder?

Actually I've never heard of it for anything but blackpowder. That was the idea behind the Mini Ball that was introduced in the Civil War. Your lead bullet would have to be soft, as in nearly pure I think. (May be wrong on that one).
That was for the Springfield and Enfield muskets. I've never heard of loading a cartridge with one, but that doesn't mean it hasn't happened.

 

[whughett]

What does the ridge in the bullet do?

Is that so you can rub lube around it? or does it help the seal?

The ridges are called driving bands and are the only part of the bullet to engage the rifling.The number is determined by the number of lube grooves.

 

[rodwha]

"The problem with a cap and ball revolver has always been achieving a maximum ratio between bullet size and powder capacity. I would think, the closer a bullet comes to a geometric cylinder, the better the ratio between bullet mass and powder capacity."

Can you explain this a little a more? Especially the geometric cylinder. By this a somewhat WC design? And is this to achieve maximum weight by not giving up room with a SWC (or otherwise) nose profile, and a flat base? If so that is one reason I like the WFN type design, but also because the entry hole is rather large, and any expansion from the lead starts there and gets bigger.


I'm curious as to what differences you see in the wide flat nose design and a WC.

 

[StrawHat]

Actually I've never heard of it for anything but blackpowder. That was the idea behind the Mini Ball that was introduced in the Civil War. Your lead bullet would have to be soft, as in nearly pure I think. (May be wrong on that one).
That was for the Springfield and Enfield muskets. I've never heard of loading a cartridge with one, but that doesn't mean it hasn't happened.

The 50-70, 45-70 and 45 long Colt were originally loaded with cup based bullets. Not so much to seal the bore but to allow the right length of the bullet for accurate rifle work. Not sure why in the revolver cartridge.

I am sure others also used a cupped base.

 

[Rattus58]

I contacted Tom at Accurate Molds and asked that he design a light weight .45 cal bullet to use in a cap n ball pistol that the OAL would be roughly that of a ball. This idea cap about after having read someone using a .45 Colt 155-160 grn bullet. The idea that it was roughly the same length, which wouldn't take up any powder capacity, yet have more bearing surface should/would (don't recall if it was theory or observed) increase pressure and velocity.

What he came out with was a 180 grn (WW) bullet .460" OAL.

http://www.accuratemolds.com/bullet_detail.php?bullet=45-180S-D.png

He also designed a lighter bullet and came up with a 160 grn variant.

http://www.accuratemolds.com/bullet_detail.php?bullet=45-160B-D.png

Next will be a heavier bullet ~250 grns in weight with a slightly wider meplat.

I've also asked him to design a light weight bullet for the .36 cal pistols.

What are your thoughts on the 160 and 180 grn bullets working in both the slow twist and faster twist barrels of cap n ball guns? Is there any reason to believe it won't be stable?

I would question stability in a slow twist rifling and a short barrel just thinking about it, but square bullets like a round ball, are easier to stabilize than long, but still need stability. One thing I noticed when looking at some of the tests with various conicals, some by the duelist, is that FOR HUNTING some bullets seem to give it up once they hit something. However, I'm looking for something that might actually be better than a round ball which I've got to say, hunting with them for almost 20 years now, though for what we have in Hawaii, big axis deer might be the only challenge or really big pigs. (right now revolvers are not legal for hunting without dogs.... stupid ... but that's our DLNR)

Aloha...

 

[rodwha]

I've read several accounts of medium game (whitetails and hogs) being taken with RB's from percussion revolvers. Often the ball either exits or is found under the hide.

After having seen that this 180 grn FN is only the length of a ball, and won't take up any more powder capacity (maybe a grain or so), I'd think that it would have an ever greater wound channel and better penetrating capabilities than a ball. For something that isn't big or dangerous I'd think it would be quite good.

But I'm also having him design one that's ~250 grns for hunting things that you'd want great penetrating qualities from.

The slower twists are designed with short RB's in mind, right? Why would a slower twist be more questionable?

 

[Rattus58]

I've read several accounts of medium game (whitetails and hogs) being taken with RB's from percussion revolvers. Often the ball either exits or is found under the hide.

After having seen that this 180 grn FN is only the length of a ball, and won't take up any more powder capacity (maybe a grain or so), I'd think that it would have an ever greater wound channel and better penetrating capabilities than a ball. For something that isn't big or dangerous I'd think it would be quite good.

But I'm also having him design one that's ~250 grns for hunting things that you'd want great penetrating qualities from.

The slower twists are designed with short RB's in mind, right? Why would a slower twist be more questionable?

If you're referring to me, the shorter the barrel the less velocity you are able to develop. Any bullet/ball needs a certain rotation to achieve the best accuracy. For shooting at something 10 feet away, a smoothbore would probably suffice. In my opinion the shorter the barrel the faster the twist required for accuracy and penetration. Also, the smaller the bore the faster the twist required to properly stabilize the bullet/ball.

This is from greenhill's formula to give you an idea...
=<1800 fps
120
Diameter 0.45
Bullet Weight 141
Bullet Length 0.45
Twist Rate 54
Sectional Density 0.099470899

=<1800 fps
120
Diameter 0.58
Bullet Weight 280
Bullet Length 0.58
Twist Rate 69.6
Sectional Density 0.118906064

When you look at the above twists greenhill suggests, it equates to a revolutions per minute/second etc. If a 32" barrel produces 1400 fps, for example and that stabilizes with a 1:70 twist.. if that is optimum (Rev's per Second) then if you reduce velocity to 1000 fps, shorter barrel lets say or maybe you don't don't want to have a 90 grain load in a pistol, you'll need a twist rate of 1:50

twist 70
fps 1400
rps 20

twist 50
fps 1000
rps 20

In my humblest of opinions...

 

[rodwha]

I often figured that velocity had something to do with stability, but have been unable to find answers.

The twists you provided, are they from a calculator? If so can you provide a link?

 

[rodwha]

I found a twist calculator, but when I type in a typical 45 Colt and ACP load it states that the twist ought to be quite slow. Much slower than what any manufacturer produces. Are these formulas not consistent with handguns?

For a .452" bullet to work in a 1:18" twist as my ROA barrel has, the bullet would need to be 1.18" long at 850 fps.

 

[Rattus58]

I often figured that velocity had something to do with stability, but have been unable to find answers.

The twists you provided, are they from a calculator? If so can you provide a link?

I took the published greenhill, talked to those who are into ballistics way more than me to see if I could come up with something that relates to muzzleloader velocities and this is what I got and use with an excel program...

for velocities of less than 1800 fps use 120.
formula is (120/bullet diameter)/(bullet length/bullet diameter)

For velocities of more than 1800 and less than 2800 fps use 150 and more than 2800 use 180.

 

[Rattus58]

I found a twist calculator, but when I type in a typical 45 Colt and ACP load it states that the twist ought to be quite slow. Much slower than what any manufacturer produces. Are these formulas not consistent with handguns?

For a .452" bullet to work in a 1:18" twist as my ROA barrel has, the bullet would need to be 1.18" long at 850 fps.

Right here you can see that shorter barrel length requires faster twist when you factor in RPS. Using your example of 850 fps and a 1.18" bullet length, greenhill would estimate a twist of 1:20 at least. 1:18 would work just as well and also with longer bullets. But that is with velocity say of 1400 to 1800. Revolutions per Second. A round ball twist for a rifle is approximately 1:54 for a 45. Does 1:48 work.. yes... again one of those compromise situations.

Revolutions per second say at 1800 fps and 1:54 twist equals roughly 33 revolutions per second. To get that RPS at 850 fps you need a twist rate of roughly 1:25, yours at 1:18 gives you some lee way on the positive side.... again, in my opinion...

Much Aloha,