Green Mountain T/C Replacement Barrel

[Hairy Clipper]

I am very intrigued by the premise of your situation and it is one we hear talked about quite often. The question has caused me to search for the ballistic coefficient for round balls as well as utilize one of the many projectile stability calculators that a number of bullet manufacturers have in their websites to help bullet buyers pick optimum bullets for the twist in their rifles. After punching some numbers in it would appear that the 1-48" twist is better than the much revered 1-66" twist rate assuming 2,000 fps muzzle velocity in either the .50 or .54 caliber round ball. In fact the calculator below tells us 1-66" twist barrels are marginally stable

Ballistic coefficient for spheres

Twist rate calculator

Of course I could be wrong ... .

 

[Alaskan Woodsman]

Interesting Hairy. Guess I'll keep that barrel on that rifle and look for an additional gun. Oh boy

Thank you, for the links. Much appreciated!

 

[Zonie]

IMO, a roundball is inherently stable.

Long objects like bullets are not.

This makes things like Twist Rate Calculators useful if one is shooting bullets but useless if one is shooting patched roundballs out of a rifle.

 

[necchi]

This makes things like Twist Rate Calculators useful if one is shooting bullets but useless if one is shooting patched roundballs out of a rifle.

Exactly.
There is simply too much history of firearms and round ball use that evolved into modern firearms as we have to ignore.
It's like trying to re-invent the wheel.

p.s. Hairy Clipper,, there's a bunch of us here that load for CF too. Shooting patched round ball is not rocket science, loading for CF bullet is.
That's the fun of traditional muzzle loaders, :wink:

 

[Griz44Mag]

p.s. Hairy Clipper,, there's a bunch of us here that load for CF too. Shooting patched round ball is not rocket science, loading for CF bullet is.

We have 150+ years of data on CF as well. It's not rocket science either. And I too load for all of them, including 1k PRS. I will say that I have had more fun with the BP in the last year than with the "others", but all the formats are enjoyable. I won't be giving up on any of them, including the pointy sticks with feathers.....
TX GRIZ

 

[Alaskan Woodsman]

That is interesting Zonie. So I shouldn't consider rate of twist for shooting round ball? Or is depth of rifling more important? Thanks!

 

[Kansas Jake]

I can't answer for Zonie, but a twist rate calculator may or may not have an application with a round ball.

What most here would say is that with a round ball rate of twist and depth of rifling are important considerations for a patched round ball rifle. Deeper rifling is usually more accurate than shallow and a slower twist will be more accurate with higher powder charges. Those are generally agreed to by most black powder shooters. Now having said that, TC rifles have shallow rifling but can be pretty accurate with a tight patch and ball combination.

For round ball in calibers around .45 and above will do well with rifling in the 1 in 48 to 1 in 70 range. That probably doesn't mean above or below that can't shoot well. Also typical good quality barrels will have a depth of rifling in the .010 to .012 area. Again, that doesn't mean a barrel outside that range can't shoot well.

 

[Zonie]

I agree Jake.

TC designed the rifling in their muzzleloaders to shoot the Maxi-Balls® and Maxi-Hunters® slugs they made and sold while keeping in mind there would be people who would want to shoot a patched roundball.

To accomplish this they made the rifling groove depth around .005 deep and used a twist of 1:48.
Fast enough to stabilize their bullets and slow enough to still allow hunting velocities with a patched roundball.

 

[Elkeater]

I'm looking at Oregon Barrel Co for a Renegade barrel. My first .58. Customer chooses length(to 35"), twist rate and rifling depth. 35" for sure. I have not talked to them yet; thinking slowest twist and deepest rifling.

 

[Grimord]

Bobby Hoyt did a re-bore for me on a Browning Mountain Rifle and he recommends a deep groove, 1:66 twist for round ball use. That what he did for me. The slow twist requires a hefty powder charge for best accuracy. I use 120 grains of 2f, with a .575 ball and a .015 patch. Sighted in 1.5" high at 50 yards, I am dead on at 75 yards and about 3.5" low at 100.

 

[Elkeater]

That's the trajectory and wallop I'm looking for.

 

[BrownBear]

I'm torn with large bore muzzleloaders, because I use them a lot with reduced loads for small game, as well as for big game hunting. I am the proud owner of five 58 calibers, two with slow twists and three with 1:48 twists. The slows with their preferred charges of 120g and 140g respectively of 2f are phenoms. But they suffer pretty badly in the accuracy department with light loads.

Meanwhile the 1:48 twists excel right up through the powder charge scale. They bash bunny heads with aplomb down at 30-40 grains of 3f, while they really flatten trajectories up over 100 grains.

I agree on the deep rifling, but if I was to put together another 58 caliber (and my wife didn't catch me at it!), I'm pretty sure I'd go with another 1:48 with deep rifling.

There's a very good reason that so many of the original rifles we admire were made with 1:48 twists, I think. The guys used them for everything, and they sure didn't want to waste a whole bunch of powder when they didn't have to. Pretty smart about things like that, they were.

 

[Rifleman1776]

There's a very good reason that so many of the original rifles we admire were made with 1:48 twists, I think. The guys used them for everything, and they sure didn't want to waste a whole bunch of powder when they didn't have to. Pretty smart about things like that, they were.

Amen, Bro.
In the museums I have visited that display nomenclature with their firearms, the twist on old ml rifles is almost 100% of the time 1:48". Military rifles do vary because generals liked to futz around with different notions and many shot elongated projectiles, not prb.

 

[Elkeater]

Thanks Brown Bear,

I don't have a smooth bore so, as you point out, this 58 can be the next best or as good for small game. And I get to know the 58 better. Do you have grouse up your way?

 

[Grimord]

Brown Bear makes a good point. I have two .58's. The Browning Mountain rifle I mentioned in an earlier post, and a Renegade with a "Big Boar" .58 barrel with 1:48 twist, This is my go to gun for hunting in real thick laurel like we have here in CT. Most of my shots are in the 35-60 yard range with this gun, and 80 grains of 3f does the job nicely. The trajectory is ok for these shorter shots, but for anything over 70 yards it becomes a matter of being able to estimate the distance to within a few yards cause the ball drop is pretty severe. I have tried boosting the powder charge of 3f and even trying 2f, but the accuracy goes to heck. Lucky to get 5 inch groups at 75 yards, and that is not good enough for me. I have to shoot thru windows in the laurel, and sometimes those window are pretty small.

 

[BrownBear]

Do you have grouse up your way?

No rough, spruce or blue grouse, but two of the three species of ptarmigan!

 

[Elkeater]

What gun do you like for ptarmigan?

 

[Elkeater]

a Renegade with a "Big Boar" .58 barrel with 1:48 twist, I have tried boosting the powder charge of 3f and even trying 2f, but the accuracy goes to heck. Lucky to get 5 inch groups at 75 yards, and that is not good enough for me. I have to shoot thru windows in the laurel, and sometimes those window are pretty small.

I suspect shallow rifling for the poor accuracy at higher velocity. If the Big Boar is of shallow rifling?

 

[BrownBear]

What gun do you like for ptarmigan?

Everything I own! I've shot them with 30, 32, 36, 44, 45, 50, 54, 58, and 62 caliber rifles, 20, 12 and 10 gauge shotguns, plus about every caliber of modern gun you can name. Head shots with anything rifled and on the wing with smoothies and shot. Limit is 20 per day and the season runs from August to April.

 

[necchi]

Limit is 20 per day and the season runs from August to April.

:shocked2: Wow, they must be prolific breeders.