.62, Forsyth rifling, hard and soft round balls, musing on the rate of twist

[Philip A.]

For those who have tried that, and seen what happens, good or bad... Here is the question: 28" barrel, .62, with Forsyth rifling, to shoot pure lead and hardened lead balls. Hunting loads, 100gr to 140gr, 1400 to 1600 fps, maybe 1700-ish. Now, Forsyth talks about 1:104 twist, but that's for a 14 or 16 bore, and to get the largest charges possible. For a 18 bore, he talks of 1:86. So for a .62/20 bore, logic dictates that the rate should be around 1:70-1:76.

Searching around, what I saw ist that most of those having Forsyth rifling in a .62 are using a slower twist, in the 1:90+ region. I wonder if that's one of the reasons why some swear by Forsyth rifling, while others can't get their shots to land twice in the same county?

Is there someone who tried and tested different twist rates in .62, with Forsyth-style rifling, i.e. 7-8 grooves, shallow, 1:5 or smaller land:groove ratio?

And since there is no "New here, how y'all doin" thread, I'll just greet formally in this my first post... Hi everybody, I live in East Africa and really appreciate the level of technical knowledge one finds on this forum, I have already gathered tons of very useful info. Thanks all!

[Daniel Coats]

Not sure how helpful this will be because my experience is 25 years old. I had one in 20 bore and the twist rate was about one turn in 10 ft and used 200 grains of powder shot flat and was very useful on blowing up rocks the size of a basketball. Never got around to hunting with it but always meant to.

[Bsharp]

I have a Rice .62 with a 104 twist.

Early testing shows that it likes 135- 150FF. .620 PRB.

Also shoot a .610 hard ball with two wrap of printer paper.

I will post pictures later.

[Hungry Horse]

 I think you may not get performance out of a Forsyth barrel that only 28” long. With those large charges, you’re only effectively using about twenty five inches of barrel.
 A friend of mine bought an old Hawken full stock up in Montana that was all tacked up, and obviously had some long hard miles on her. But it had a Bill Large (Forsyth style) barrel in .54 caliber that was 41” long. I’ve never seen a more accurate muzzleloader. He hated the weight of that gun, so he built a brand new half stock Hawken with Roller lock, and triggers, but a standard style barrel that was shorter, and built by Les Bauska. It shot well, but couldn’t match the old full stock off the bench.

Hungry Horse

[smylee grouch]

My 62 with a  1-85 inch or so does well with 110 of 1&1\2 Swiss getting 1784 fps.

[Daryl]

I think Dan's 16 bore has an 85" twist and shoots best with 140gr. Swiss 1 1/2 for 1,700+fps.
My .69 shoots well (about the same)with from 140gr. 2F to 200gr. 2F GOEX. The 200gr. charge developed 1,700fps.
66" ROT.

[Bsharp]

This is a target overlay of three different targets.
1-1 is the patched first shot then followed by a paper patch loaded dirty. [1-2]
2-1 and 2-2
3-1 and 3-2
I just wanted to see how the follow up paper cartridge would group compared to the first patched load.




Paper cartridge

[Dphariss]

I would go no slower than 80”. It would be best IMO with 10 grooves. .008 or a maybe little deeper.  But no more than .010 deep. I used a early ballistics program and using his tested trajectories go about 1600 FPS with 14 bore using a#15 ball with 137 gr of “Halls #2” powder. Probably fff. He wrote that from his short barreled rifle he could drive a hardened ball through an Indian elephants head from side to side. Memory says it was 26” long but I am not home right now to look it up. John Taylor was killing African elephants using lung shot with 167 gr of powder from a 10 bore. Its in his book “Pondoro”. It was a smooth bore percussion.

[Philip A.]

This is a target overlay of three different targets.
1-1 is the patched first shot then followed by a paper patch loaded dirty. [1-2]
2-1 and 2-2
3-1 and 3-2
I just wanted to see how the follow up paper cartridge would group compared to the first patched load.




Paper cartridge

Bsharp, that's great info... Where do the different projectiles end up, excatly what one needs to know!

My 62 with a  1-85'or so does well with 110 of 1&1\2 Swiss getting 1784 fps.

1784 fps with only 110 grains? What barrel? These are good numbers!

[smylee grouch]

That is a Jim Carpenter barrel. Not Forsyth rifling, 7 cuts that are about equal to lands and 10/1000 deep.

[Daryl]

I used a early ballistics program and using his tested trajectories go about 1600 FPS with 14 bore using a#15 ball with 137 gr of “Halls #2” powder. Probably fff.

In my testing, Dan, I found just about identical trajectories using a .682" ball ('bout 14 1/2 bore). In my 31" bl. 3F gave lower vel. Mine ran 1,550fps with 165gr. My 14 bore
rifle shoots equally well with a #15 ball (.677") when using a 14 ounce denim patch, I measure at .034".

[Waksupi]

I had Jerry Cunningham cut me a 1-120 .62. It took 180 gr. 3F to perform well, and killed on both ends in a 7.5 pound rifle.

[Hungry Horse]

 I’m working on a rifle right now with a barrel Jerry Cunningham built that is .62 with a 1 in 72” twist. I got the barrel as a second because one of the flats was a little irregular.

Hungry Horse

[Daryl]

I found my paper ctgs shot identically to a patched pure lead ball. The paper ctgs had the same dia. ball as the patched ones  but with a WW alloy ball. They shot into the same group at 100 meters.

[Bob Gerard]

I am surprised a bit at how much powder (130 grains) is used for something in the .62 cal range with very slow twist (+80).
Initial results with my .62 with a 1:72 twist showed it shooting quite flat with 80 grains of 2f out to 100 yards, then about a 2 foot drop at 200 yards.

Oh., and blowing up large rocks sounds like fun😁

[Daryl]

80gr. 2F in a .62, should produce around 1,300fps and have around a 5" to 6" drop at 100yards if zeroed at 50.
If 3" high at 50, the ball should be close to zeroed at 100, seemingly quite flat shooting.

[maudite]

I have this rifle built by RJ Renner in 62 cal with Forsyth rifling.Though I can t remember the twist rate Renner told me that it could shoot either round ball or conical.I have only shot round ball out of it with a 120 gr ffg load for hunting.I would would contact RJ Renner as he has lots of experience with the use of Forsyth rifling and he could probably help you out on the subject of what twist you want

[Daryl]

The typical ball for a 14 bore with the so-called Forsyth rifling was 1 bore size smaller ie: a 15 bore ball. That would mean a .675" to .680" ball in a .690" to .695" bore.
Nominally 15 bore is .677" & 14 is .693".
With this line of thinking, a 21 to 22 bore ball would be good. This will allow any hardness of ball with a substantial patch.