| Ash |
| (.400 member) |
| 30/04/17 09:57 AM |
10 Bore twist rate?
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Hey guys,
Wondering for a black powder muzzle loader (actually it's a Ferguson..) what twist rate for a 10 Bore and what powder charge? Probably just be a round ball gun.
| DarylS |
| (.700 member) |
| 30/04/17 10:56 AM |
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Re: 10 Bore twist rate?
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Anything around 66" would suffice. Any slower will take too much powder to get it to work.
For a Ferguson Rifle, restricted to about 100gr. of powder, I'd likely stick with something in the faster 66" to 75" range.
That rate of twist also works well with anything as small as 50 cal.(38 bore)
| CowboyCS |
| (.333 member) |
| 30/04/17 12:06 PM |
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Re: 10 Bore twist rate?
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Cox's formula - bore diameter times pi divided by .029 = twist rate
.775 x 3.14 / .029 = 83.91(1:84 makes a nice round number)
Rayl's formula - bore diameter times pi divided by .02618 = twist rate
.775 x 3.14 / .02618 = 92.95(1:92 is a nice even number)
I usually go with the Cox rate the faster twist is usually just fine for big bore rifles.
These formulas are for roundball rifles, for bullet rifling look up the Greenhill formula as a starting point.
As for loads I would probably start at 70 grains FFg and work up from there until I found the best accuracy.
I hope this helps.
Colin
| Ash |
| (.400 member) |
| 30/04/17 02:01 PM |
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Re: 10 Bore twist rate?
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Thanks, guys!
It's 1.25" across flats at the action (octagonal barrel). Suggest a taper and length also? (aint i being demanding!)
| DarylS |
| (.700 member) |
| 01/05/17 02:41 AM |
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Re: 10 Bore twist rate?
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I initially considered the slower twists as recommended by Forsyth - but in deference to the increased powder charges normally needed to gain accuracy with them, I suggested faster twist rate. My 14 rifle shoots as well with 140gr. through to 200gr. Even 140gr. with a 700gr. 10 bore ball is going to get your attention. It is doubtful you will get good accuracy with light charges, even in the faster twist. I would think 120gr. to be a minimum charge.
This 'light' load shoots well in my buddy's 11 bore rifle, but for shooting past 50 yards, as in 100yard target or for hunting, he uses 150gr.2F. That is in a Don Getz 66" twist barrel. he initially started with 200gr. 2F as that shot well - it also kicked well in the 9 pound rifle, so he reduced to 150gr. for hunting moose. That rifle & load simply staggers them.
If a person was going after buffalo, elephant or tigers, then perhaps the slower twist would be OK due to the greater powder chargers.