Twist rates

[Solomoriah]

I got about a half dozen old inline rifles off Gunbroker to do powder testing and general plinking with. Totally random lot bought because they were all under $100.

They came with anything from 1:20 to 1:32 twist. Why does it vary so much? That 32 twist rifle has deep grooves as well, seems to have ben intended for plain lead bullets and not sabots. According to the formula I have I can't put more than 20 grains of powder in those 20 twist rifles without the projectile stripping off the rifling (or use "Golden Powder" which is about half the strength of black). The 32 twist rifle I can actually use for serious shooting. The rest of mine are all 28's and its kind of a toss up.

 

[ElDiablo]

 

[trickyricky]

I dont know where you got the idea about a 1/20 twist being useless. A fast twist is considered better for heavy (long) bullets to stabilize the projectile.
Slower twists up to about 48, will shoot conicals if they arent too heavy.
Above 48 are generally considered round ball shooters.
The 28 twist is a good all around middle of the road, it will handle sabots and conicals too.
My Whites are 20 and 24 twists for 451 and 504 calibers, my .410 is a 16 twist.
All are excellent shooters with heavy charges. The 410 shoots about 1550 with a pure lead conical weighing 338 grs.

 

[trickyricky]

View attachment 42834

Lol! Too late!

 

[smokepolehall]

All of those twists are good. You now have lots of testing n load work to see what each likes. In general the slower the twist the shorter length of bullet. I have a 1:20 twist in my .45, it will not stabilize any of my land riders past .850 in length at low to mid lvl powder charges

 

[michiganmuzzy]

Make some smoke Solomoriah, I'm interested to see where your testing takes you. I’ve been learning that the type of rifling(shape, depth, width, how they were made) will have as much effect on how it shoots different bullets, as twist rate does. Are all you barrels the same caliber? .45 or .50? Are you testing groups of jacketed, lead and sabots? For some bullets a lighter load won’t make it expand enough to grab the rifling.
I might try this test with sabots as imho, they are the most versatile and forgiving of twist and type.

 

[ElDiablo]

Are all you barrels the same caliber? .45 or .50?

That was my first question. Six inlines of the same caliber with twists from 20 to 32?

 

[michiganmuzzy]

That was my first question. Six inlines of the same caliber with twists from 20 to 32?

They could all be Traditions. They’ve made all those twists and are not very expensive.

 

[Solomoriah]

They could all be Traditions. They’ve made all those twists and are not very expensive

All of them cost under $100, some were rusty or needed work to make them functional. Just hobby stuff. I saw them this cheap on Gunbroker and with no FFL fees involved couldn't resist. I had to make parts for some of them. About half have wooden dowels from Home Depot as they had no ramrods - probably sold after someone shot it out of the gun. I can make a replacement ramrod for under a dollar so no big deal.

I do not shoot Sabots, only the occasional Minie. Mostly round ball, even in these. The maximum powder charge in standard black powder being the formula: twist rate X caliber X 2. So for these .50's with a 20 twist rate, 20X.5X.2=20. The heaviest powder charge I can use with a round ball in a .50 rifle with a 20 twist is 20 grains.

Super cheap shooting considering I make the powder, ball & caps all myself. Some of these take 209's but I got a big case of those French primers so I'm set there

 

[smokepolehall]

I reckon as a standing formula thats ok. Just not exactly so set in stone. I have a T/C .50 1:28 twist that will pop 2" group at 75 yds all day long with 70 gr 3f Goex prb

 

[Solomoriah]

I reckon as a standing formula thats ok. Just not exactly so set in stone. I have a T/C .50 1:28 twist that will pop 2" group at 75 yds all day long with 70 gr 3f Goex prb

I was trying to fire PRB from a 1:20 twist with 60 grains and at 10 yards it was a dinner plate size group. This is with a scope fired over a rest so it wasn't me. I'm going to start backing off in 10 grain increments until it actually gives me a usable group. With 60 grains neither Minie or round ball work

I got a clue when the powder clumped and one load only got about 30 grains. It sounded like a squib but the ball did hit the target below - and dead center under - the bullseye. So the usable load is somewhere between 30 and 60.

 

[smokepolehall]

Powder clumped ? Moisture ? Its a trial n error trying prb's out of faster twists. You may find a decent load & power