Help me design a heavy boolit please

[Spokerider]

I's looking for input on designing a heavy boolit for my carbine please.

The gun is a Uberti Baby rolling block .357 mag that I have reamed to .357 max with a Manson chamber reamer. This chamber now has a short throat, and not a long pistol-type throat, although the Uberti .357 mag throat wasn't too bad / long anyway..... The carbine has a 22 inch barrel with a 1 / 16 twist. I want a heavy boolit for sub-sonic loads, around 900 to 1000 fps. The load will be used for cougar hunting, and possibly, but hopefully not, dispatching a black bear that may be trying to kill my hounds. This is my packing gun. The shots will be close range, from point blank to 50m.

Been playing with the Mountain Man mold program a little and have some questions regarding boolit design, specifically where the center of gravity ought to be in a boolit and questions about the number of lube grooves, ratio of the lube groove width to band width, angle of lube groove walls, and what difference the length of the crimp groove makes?

I currently shoot Cast Performance 180gr bullets crimped in the crimp groove in the .357 max cases, and the cartridge *just* makes it past the rolling blocks when loading. The nose on these bullets is .290 long, so I'm thinking I need to stick with a nose lenght design .300 or shorter. For the nose, I'm considering a front band length of .060 in secant shape, with a 75 % meplat. Not sure on the lube groove and band design options though......

Wanting the heaviest plain-base boolit the barrel will take........appears to be approx 240gr.
The ought to be plenty of room in the .357 max case for powder considering the modest velocity needed.

I don't have a sizing die, but will get one if it is a must.

Your thoughts on boolit design please?

Thanks.

[PacMan]

I may be wrong but 240 gr. in the 1-16 twist may be a little long. Should be ok at the horter distance but if you need to reach out longer range there may be a problem. Hope that some one else here can shed more light than me.

Some of what i am basing my thoughts on are that i have a H&R with 1-18 1/2 twist and have never got 200 grain FN bullets to shoot very good past about 75 yards. Shoots 160 and 180s great but not the 200.

[Spokerider]

On the Mountain Man mold design program, the barrel twist is listed as you enter the parametrs for your design. The twist changes as the bullet weight and design changes too.

240gr is about the maximum weight that the program lists for 1 / 16 twist, basen on my parameters. Not sure how accurate his equation is.......... the info about his twist program is;

This uses a constant of 150. It does not predict the instability that sometimes occurs with blunt, short revolver bullets.

The formula is: maximum bullet length = diameter x diameter x 150 / twist

The online design program's suggested twist uses a safety factor of 1.3. This gives a good ballpark number but it is not intended to be the final word so don't lose a lot of sleep worrying about it.

[PacMan]

Just another thought. I assum that the bullet will be cast soft enough to expand at that velocity. If not just poking a .359 hole thru him at 900fps wil most likely leave some fight in him. Good dogs arent cheap as you most likely know.
Let us know how the design works out.

[Doc Highwall]

I would look at the RCBS 200 gr Flat Point first then the Lyman 358315 205gr RN second.

[Norbrat]

I use Cast Bullet Engineering's 358-200 GC Sil mould, which drops them at about 215 with my alloy, in my FA 357 Mag to shoot silhouette. Works very well, and accurate.

I used to use it in the Wesson Arms 357 max, but the gun was not accurate enough; it would start to "walk" to the right and low after about 25 shots.

Anyway, CBE's website is a bit basic, but a profile of the bullet is here http://www.castbulletengineering.com/page0041.html (scroll down to about the third last page.) Also have a look at "Update No 2, Page 1" about the third page; there is a 358-250 GC design there.

Have a look around the website; Jim has a range of dia 357 - 360 designs. Within reason he can make GC designs as PB and vice versa, and custom make to your design.

If you want some samples of the bullet I use, PM me and I'll send you some.

[runfiverun]

i use the saeco 250 gr boolit in my 357 max revolver.
i'd look at modifying that by shortening the nose.

[Spokerider]

Norbrat,
Thanks for the info and the link.
Those are interesting looking bullets. They have long noses, and I really doubt that I would be able to chamber cartridges with such long noses around the rolling block. I can just load my 180gr Cast Performance rounds with a little wriggling.........

Still wondering about the correct placement of center of gravity of a boolit, nose heavy? Base heavy? and how the CG affects bullet stability.
Also, considering the Mountain Man mold design program allows for lube groove and land numbers and ratio's, groove wall angle, etc, wondering what the parameters are for selecting the options best suited to my needs?

My questions may be rather moot considering the intended use and range of the boolit, but I still would like to choose the options that will foster the *best* performance of the boolit.

[Mk42gunner]

What about a PB version of the Lyman 358627? A 215 grain SWC that was designed for the .357 Max. It has a nose like a 358429 with two crimp grooves.

Robert

[Norbrat]

Norbrat,
Thanks for the info and the link.
Those are interesting looking bullets. They have long noses, and I really doubt that I would be able to chamber cartridges with such long noses around the rolling block. I can just load my 180gr Cast Performance rounds with a little wriggling.........


As it's a single shot, you don't need to crimp, so just shove the bullet into the case as far as you need to. As you said, for those velocities, you will have plenty of space for the powder.

That bullet I use has a crimp groove perfect for the cylinder length of the Wesson 357 max and it happens to also be just perfect for the long cylinder in the FA 357 mag.

But I've also loaded the same bullet for a friend's S&W, and crimping in the crimp groove would have made the OAL way too long for that cylinder, so I just crimped on the nose as needed. The ammo shot almost as accurately in his gun as it does in mine, and that was likely more due to the gun than the ammo.

CBE's 359-210 GC is designed for the 357 mag cylinders with the crimp groove closer to the nose.

I don't know much about bullet design, but generally it does seem that hollow pointing secant nosed J-words improves accuracy potential. This would move the CG closer to the rear of the bullet. Whether this is as true for cast boolits.... <shrug>

As you say, it's probably all a bit academic; if you want a such a heavy 357 bullet, you won't be able to do much beyond a bore riding, fat bullet anyway.