twist rate

[smylee grouch]

I will be having a barrel made in .660 cal to shoot a .645-or .650 ball. Can some one give me an idea if 1-85 twist is going to be fast enough or slow enough when shooting 150 gr. of Swiss 1&1/2 powder for up to 150 yds. or so.

[sqrldog]

SG I've had the twist recommendation conversation with Bobby Hoyt. I would think he is about as knowledgeable as anyone on the subject.  His formula for twist in a round ball gun used for hunting is caliber plus one forth of the caliber. In this case 66 plus one fourth of 66 (16.5) equals 82.5. So one turn in 85 would be really close. With that said he also makes gain twist barrels. I have one in .60 cal that I really like. Talking with some of the barrel makers about their experiences with twists in his particular caliber might be worthwhile.  Tim

[smylee grouch]

Thanks for that info Sqrldog, I have never heard of that be for but it does come out close to my WAG of 1-85. I know if I make it a slower twist it would still shoot ok with larger charges but I think a 400 gr. ball with 150 gr. charge will do just exactly what I have intended for it in my recoil range and the projected 10# or so gun weight.

[Daryl]

My .69 does very well with from 140gr. to 200gr. no change in accuracy. It has a 66" twist in a GRRW barrel, purchased in 1985.
With a mere 82gr. to 85gr. is shoots very well at 50 yards too. My rifle weighs Forsyth's optimum 9 1/2 pounds with 31" 1 1/8" straight octagonal bl.
If I were to make up another 14 bore gun on Forsyth's principal, I would opt for an 85" twist, myself. Dphar and I had quite a conversation
about this some time back and he is also in agreement on the 85" twist, rather than one that is slower.

[smylee grouch]

Thanks for the input Daryl, I wanted some thing that I could shoot moderate loads in but yet still stabilize a more substantial load for moderate range on heavy game but still with in my recoil tolerance with a 10# gun. The 1-85 rate must have been in my mind from past discussions on this site. Now just to get the right specs for the out side of the barrel to end up with a 10# gun.  

[Daryl]

Since you use decent ball and patch combinations, I'm positive you can get away with just .008" rifling if wanted. Mine is .012" in 66" twist. I'm sure it's deeper than needed, considering what

I use (what it likes) for combinations.

[smylee grouch]

Good point on the depth and I had considered that, say 8 or 10 thousands deep instead of 10 to 12. I suppose that if I thought my loads were striping I could send the barrel back to have them deepened .

[Daryl]

I would expect that with 85" rifling, 006" to .008" would be sufficient for any powder charge you are expecting to use.

Once you get to 16 bore size, getting around 1,700fps is about it. I think Dan gets that out of his 16 bore using 140gr. Swiss 1 1/2F(I think).

Using GOEX, I was able to hit 1,700fps at 200gr. in my .69. The 66" rifling worked just fine - about .012" deep, using .682" ball and .030" (12oz.)denim.

A few shots later, I accidentally double charged my normal moose load (165gr.), for 330gr. 2F GOEX and the chronograph read 1,770fps. It also lifted me into a

 standing position over my chair. I guess my barrel got proofed that day.

[Daryl]

I will be having a barrel made in .660 cal to shoot a .645-or .650 ball. Can some one give me an idea if 1-85 twist is going to be fast enough or slow enough when shooting 150 gr. of Swiss 1&1/2 powder for up to 150 yds. or so.

Seems to me, and if I remember correctly, Ed Rayle will make a barrel sufficiently over .662", that you can use the standard 16 bore ball, .662" - by Lyman. I think they are .670" in the bore.

Dan (Dphar) might have more information on that.

[smylee grouch]

Boy oh boy Daryl, shooting 330 gr of powder behind a 480 gr ball would be somewhat spiritual for me.  I will be shooting (no pun intended) for a 400 gr. ball and .645 should do it and I'm sure it will be at or near my recoil tolerance peak. 58 cal was always my gun for moose,elk, and bear and it worked but what a 58 can do a 66 can do better IMHO. Thanks for all the input and specs. 6 months or so before I get the barrel, now to find the walnut I want in the size I need.

[Daryl]

Best wishes on your build.
My old .58 Hawken with the B. Large barrel shot quite well with a modified $57730 mould casting a
675gr. Minnie with 150gr. GOEX 2F for 1,250fps and 160gr. GOEX 2F for 1,325fps.
The recoil was quite nasty with that hooked, narrow butt plate.

[smylee grouch]

Coincidence but Bill Large made three barrels for me in the real early 70s and one was a 58 with a Hawken style breech. I told him I wanted to shoot a 570 ball and he made up the barrel to shoot the minnie but told me it would shoot the ball ok too. It did shoot the ball ok but I never tried the minnie.

[varsity07840]

My .69 cal percussion round ball rifle has a 1:90 twist with shallow grooves. It needs a least 140 gr of 2F for 100 yard accuracy. Out to 50yds, 120 gr works fine, but it's all over the place at 100. I think barrel length relative to twist is a contributing factor. As an example, I have two original rifled 1842 Springfield muskets, one with a full length 42" barrel and the other that was cut down to musketoon length when it was a smoothbore. I had Bobby Hoyt line and rifle it with the same twist as the full length gun, 1:72.  At 100 yards, 70 gr of 2F and a semi wadcutter 500 gr minie, the full length gun groups very nicely while the short barrel with the same load won't keep them on the paper. I built a Richmond Carbine from an original 1861 Springfield with a bad bore and Bobby put a 1:48 twist in it. When I asked him why he said that's what most N-SSA shooters want for short barrel guns. He was right.

[smylee grouch]

That's interesting Varsity as my rifle will have a somewhat short barrel, thinking of 28 inches right now. 

[RichG]

It's not really the length of barrel it's the relationship between velocity and twist. Of course barrel length will contribute to velocity.

[Blacksmoke]

Hi Smylee,  My experience has resulted the following formula ; "the larger the ball the slower the twist" With a cal. of .600 or larger I would choose a twist rate of 1X85" or 1X95".   Hope that helps,  Hugh Toenjes