OPTIMUM ROT FOR .54 CONICALS?

[4570steve]

ANYONE KNOW WHAT THE OPTIMAL RATE OF TWIST IS FOR SHOOTING CONICALS IN A .54 CAL? I SAW IN THE FOX RIDGE CATALOG THAT THEY OFFER A 1-48" TWIST FOR THE .50 CAL ENCORES. I HAVE A BMM THAT HAS, I BELIEVE, A 1-34" TWIST. WOULD I BE BETTER SUITED WITH A SLOWER ROT? ALSO, ANYONE KNOW WHY THE BMM'S SEEM TO HAVE NEVER MADE IT OFF THE GROUND WITH T/C?

 

[jtmattison]

Well, I don't know what a BMM is for starters but a faster twist is good for conicals.
I shoot a 1:32 twist Lyman GPH with 430 grain Maxi-balls I cast and they shoot great.

HD

 

[Rebel]

I think BMM is Black Mountain Magnum.

 

[shifty-eyed_one]

...a faster twist is good for conicals.
I shoot a 1:32 twist Lyman GPH with 430 grain Maxi-balls I cast and they shoot great.

HD

So am I right that a 1 in 48" is not going to work as well for Maxi-Balls? I was under the impression that unless you used the sabots or longer conicals, 1 in 48" would work pretty well.

bmanilow

 

[jtmattison]

...a faster twist is good for conicals.
I shoot a 1:32 twist Lyman GPH with 430 grain Maxi-balls I cast and they shoot great.

HD

So am I right that a 1 in 48" is not going to work as well for Maxi-Balls? I was under the impression that unless you used the sabots or longer conicals, 1 in 48" would work pretty well.

bmanilow

I have not been able to get what I consider good accuracy from conicals in a 1:48. I get very good accuracy with patched roundball out of the 1:48.

My 1:32 twist barrel is the only one I get tight conical groups out of.

HD

 

[ryoung14]

I've got a couple of .50 BMMs and like them. Excellent conical shooters. Tough as nails.

They have 1-in-28 twist (the .50s do anyway) and were marketed as a sidelock that offers the same level of performance as an inline. They're supposedly able to shoot Pyrodex pellets in 150 gr. loads and the fast twist gave them good performance with sabots. They came with both a musket nipple and the standard #11 nipple. T/C recommended musket caps with the Pyrodex pellets.

I can think of a few reasons why they didn't takeoff. First of all, the black Rynite stocks are ugly and give the impression of a cheap gun. The fact that they are nearly indestructible doesn't matter to most people. Blued steel in a black plastic stock will turn off anyone who values tradition in firearms.

Secondly, ignition with the Pyrodex pellets wasn't all that reliable. I've tried pellets in mine and seem to get varying amounts of ignition delay. With loose powder, ignition is fine. A year or two later, T/C brought out the Firestorm percussion sidelock with a radically different breech design to shoot pellets. This was a tacit admission that the BMM/pellet combination wasn't all that great.

Third, the gun was really aimed at a narrow niche where inline performance was desired by the hunter but the sidelock design was mandated by law (don't ask me where, just repeating what I've heard). To most people wanting inline performance, it made more sense to simply get an inline. Inlines are easy to put a scope on; BMMs are not and look funny when you do.

I like mine for their conical shooting ability, their toughness and the ability to take really heavy loads. Though I rarely load above 100grs. of RS, the extra strength gives an added margin of safety....and that rubber recoil pad is nice too . Why don't I just shoot an inline? Well, I do at times, but the hooked breech BMM is easier to clean and maintain.

If the Loading Supplement booklet T/C packed with the rifle has any basis in truth, the BMM is a ballistic holy terror when fully utilized.
FWIW
Bob

 

[FlyFAmerica]

I've got a T/C Hawken 1:48 percussion .54 that shoots round balls well(2 inches at 50 yds) with 90 gn 2f 777 and I just bought a lee 300 gn REAL mold. Works well(2inch gps) with 90 gns of 2f at 50 yds but seem to be all over the paper at 100. Maybe it's my eyes or maybe I should try the 380 gn REAL. Huntin Dawg- where did you find a .54 Maxi Ball mold? I'd like to mold up a bunch of those and work up a load for that rifle.
Thanks,
Mike

 

[RedFeather]

It also depends on the dimensions of the conical. Theoretically, a stubby conical will do better in a slower twist, while a long and heavy one will require more twist to spin it up and stabilize it. I have an Excel spreadsheet that I played around with to determine ROT given diameter and length. Don't know how accurate it is, but it does work pretty well for roundballs which are as long as they are wide, coming up with generally accepted ROT per caliber. Here is the formula: (K*D^2)/L=TWIST where K=125, D=Diameter in inches, squared, and L= Length in inches. It's based on the old Greenhill formula and I have modified the K number because it seems to work better with the relatively lower BP velocities. (Greenhill's formula is meant to be flexible here.) It ain't perfect, but will point you in the right direction. For example, it says a .495 roundball needs a 1:62, a .400 needs 1:50, a .570 1:71, and a .360 1:45. Pretty close? You can also play with it to tell you what conical may be best for your twist. Take a .50 in 1:28. Gven a diameter of .495 it suggest a length of 1.094". A .54 with a 1:32 would be 1.18". A .50 with 1:48 (T/C twist) comes out .638" which may be why they do well with Ball-ets. What length is a T/C Maxiball? After fooling with this I began to suspect that T/C designed it's Hawken around that slug and not the Hawken brother's rifling machine.

RedFeather

 

[shifty-eyed_one]

It also depends on the dimensions of the conical. Theoretically, a stubby conical will do better in a slower twist, while a long and heavy one will require more twist to spin it up and stabilize it.

...
A .50 with 1:48 (T/C twist) comes out .638" which may be why they do well with Ball-ets. What length is a T/C Maxiball? After fooling with this I began to suspect that T/C designed it's Hawken around that slug and not the Hawken brother's rifling machine. Good point.

RedFeather

The .50 at 370 grains is about .750 from bottom to shoulder and .875 overall. Maybe the 320 grainer is that much shorter in order to more closely approximate what T/C would consider optimal.

 

[strosper]

I have had the same grouping issue with the Lee 300 gr REAL design. They group well at 50 yards (< 1.5") and are all over the place at 100 (> 8"). I have seen the same thing in both slow and fast twist barrels. (Lyman GPR and GPH barrels). Any ideas would be appreciated, at this point I have given up and moved on to other bullets, but I really would like to figure it out. The 300 gr design casts well and is easy on the shoulder.

 

[FlyFAmerica]

Scott
I've got a 380 gn REAL mold on order and when I shoot some I'll post.
Mike

 

[crockett]

Red Feather is right, the longer the bullet, the faster the rate of twist to stabilize it, so you have to experiment a bit. A slower bullet also needs a bity more twist. On a 1:48 if you aren't getting good accuracy on a long(heavy) conical try a ballette, it has more weight than a PRB and may be the answer.

 

[CoyoteJoe]

When T/C came up with the maxi-ball I poopoo the idea because, in theory, a 48" twist would not stabilize it. However, after hearing folks say they shot great, I got a .50 caliber Hawken and a Lyman mold and got 3" groups at 100 yards with the 370 grain maxi.
I was in my "magnum" phase then, so I jumped on the first .54 Renegade I saw and got 1 1/2" groups with the maxi. I didn't have a convenient benchrest, so all load development was shot from prone. Recoil of that little 54 was brutal!
The quality of the bullet is very important. I was casting my own at that time and still would do so if I were into conicals. The pre-cast maxi's I've seen are not worth the effort of throwing them away. Some of the swaged lead conicals look pretty good but I haven't much experience with them as I now shoot balls.
But what does any of this have to do with rot?

 

[Slamfire]

The key to bullet stability is rpms. Sometimes when the twist seems too slow, velocity can make up for it. :winking:

 

[Landngroove]

Thompson/Center Black Mountain Magnum, .54 Caliber, "Westerner" 1 in 38" twist. T/C Arms Catalog #28, 2001. And yes, I have had good luck shooting 430 grain, Maxi-Balls, with a 1 in 38" twist.

 

[FlyFAmerica]

Scott
I got the 380 gn REAL from TOW last night and cast some this morning. Using 70 gns of 2f 777 at 50 yds I was able to get 3 shots into 1 1/2 inches which made me really happy. I only shot 3 at 100 yds with the same load due to time constraints and had about a 6 inch group but 100 yds is pretty far for my eyes. I ought to work up the powder a little bit at a time- Does anybody have any recommendations for this conical in a .54 percussion? I think it's better than the 300 gn in my .54.

 

[Pittsburghunter]

From my limited experience I find lighter conicals work better in 1:48 twist rifles than what the factory has load data for.

For example I like the REAL 320g bullet over the 370g maxiball in the 48 twist rifle. I am not saying the 370g bullet isn't good and with a hard powder charge shoots as good but for everyday hunting and shooting the REAL is better and doesn't kill your shoulder.

I am talking .50 here but the ratios are about the same.

 

[paulvallandigham]

Work your way up to 90 grains, but I don't recommend going higher than that. The .50-90 Sharps was called the " Big Fifty" in its day, so I don't think you need to stretch a .54 muzzle loader further than this. I suspect somewhere between 80 and 90 grains you will find a load that works at 100 yds. For your eyes, put an aiming point on the target( or spotter). I like to use a white business card, and turn it on its side so it forms a diamond point against the black bullseye. You can start the front sight at the bottom of the bull, and then walk it up until that point seems to disappear in the middle of your front sight. Groups should be reduced substantially, so that you can find that best load, and not just the limit of your eyes. My eyes are getting so bad, I am putting a scope on a lever action gun to work up loads, and then will take it off and shoot the iron sights, knowing any shortcomings will be me, and not the gun or ammo. Hang in there. You are not alone.