Author Topic: .40 roundball barrel twist rate (Read 2394 times)

DanL · « **on:** May 25, 2021, 05:16:42 PM »

I am planning to have a barrel lined for .40 roundball ball square rifling. I have a 1:48 and it shoots great.

What is the consensus as to desired twist rate for .40 roundball square rifling? I prefer light loads for small game and target shooting. Probably 32” barrel on a light small rifle.

Thanks, DanL

Eric Krewson · « **Reply #1 on:** May 25, 2021, 05:22:59 PM »

GM .40 barrels are square rifling 1 in 48, I have one and it is a might fine shooter so I like 1in 48. I have another .40 but have never checked the rate of twist, I think it is a Burton barrel.

Daryl · « **Reply #2 on:** May 25, 2021, 06:37:13 PM »

My .40 had a Goodoien "Match" barrel in 48" twist with wide grooves, narrow lands, .010" deep.
It was very accurate, but no more accurate than my 60" twist GM bl. in .45 cal. They were both
1/2"ers at 50 yards form a rest.

Don Steele · « **Reply #3 on:** May 25, 2021, 09:38:03 PM »

I believe you’ll find 1:48 will be just fine with lighter loads. Folks I know with slower twist rate 40 cal bbls seem to gravitate towards heavier powder charge weights for best performance.

smylee grouch · « **Reply #4 on:** May 25, 2021, 10:08:28 PM »

I think GM also made a 40 in a swamped barrel with 1-56 twist.

Daryl · « **Reply #5 on:** May 25, 2021, 10:41:05 PM »

I will also state, that with my .40, the required powder charge for that 1/2" accuracy depended on the lubricant used on the patches.
Slippery lubes required 10gr. MORE 3F GOEX to get the same accuracy but the velocity for that load was 2,240fps. That high velocity gave
the same accuracy as the 1,775fps loads with water based lubes.

DanL · « **Reply #6 on:** May 26, 2021, 01:24:26 AM »

Thanks for the replies. I will see what land-groove widths are out there for a .40 square rifling liner. Mr Hoyt will probably know.

DanL

bob in the woods · « **Reply #7 on:** May 26, 2021, 06:46:20 AM »

Mine is a Colerain , 1 in 48 in twist, and it shoots very well. Most of my target shooting is done with 35 gr 3F , a .395 ball and .018 or .020 patching. It also seems to like 50 gr of 3F which I use if hunting coyotes.

Hungry Horse · « **Reply #8 on:** May 26, 2021, 05:01:09 PM »

Many moons ago someone posted a list of caliber to twist ratios that old gunsmiths recommended. They started with a forty caliber in 1in48” then a .45 cal in 1in56” and a .50 cal in 1in66” and ended with a .54 cal in 1in72”.

Hungry Horse

hanshi · « **Reply #9 on:** May 26, 2021, 11:14:34 PM »

I had a super accurate .40 swamped GM barrel that was 1-48".

mtlonghunter · « **Reply #10 on:** May 26, 2021, 11:50:45 PM »

My 40 cal. Has a 1 in 40 twist. A little faster than most but shoots real nice with 30 grains of 3f.

Hungry Horse · « **Reply #11 on:** May 27, 2021, 05:06:18 AM »

I would suspect a 1in40” twist in a .40 cal would be a wicked shooter at short, to medium, range.

Hungry Horse

Daryl · « **Reply #12 on:** May 27, 2021, 05:24:00 AM »

40" twist in a .40, is likely no different, ratio wise, to a 66"(69"actually) twist in a .69. Both 69" & 40", being 100 calibres.
I really don't think a 40?" twist in a .40 would be much different, load wise than a 48" twist. So much depends on the combination of components.

Standing Bear · « **Reply #13 on:** May 27, 2021, 05:59:13 AM »

I’ve shot and still own .40 caps 1:66 twist, a .48 (yes Mr Hoyt rifled it) 1:48 .013” grooves, and a .50 Douglas with 1:56 twist also .012” grooves.

The point being a .40 with 1:48 twist is fine, if the grooves are deep enough that the load doesn’t strip the patch. Shallow grove barrels are ok w patched round balls if the load is light to medium. A deeper (.010-.012”) will shoot the light loads as well as more robust loads.

DanL · « **Reply #14 on:** May 27, 2021, 08:21:15 PM »

Great information folks. Thanks for sharing.

Regards, DanL

little joe · « **Reply #15 on:** May 28, 2021, 12:36:44 AM »

Burton 40, mine is 1 in 48

smokinbuck · « **Reply #16 on:** June 01, 2021, 04:46:44 PM »

I have an 1 1/8"X34" Ed Rayl barrel on a table gun. .40 with a 1:56 ROT that shoots one hole groups with 65 grs of FFFg. .395 ball with .018 Teflon patching.

smokinbuck · « **Reply #17 on:** July 08, 2021, 09:28:02 PM »

I have a Rayl .40 with a 1:56 ROT. 65 hrs of FFFg goex is a one hole load at 30 yards, table shooting.

R.J.Bruce · « **Reply #18 on:** July 09, 2021, 10:16:07 PM »

Scott at Colerain is offering gain twist .40 caliber barrels in both the Classic American profile (42" long), and the Early American profile (38" long).

Rates of Twist
42" = 1:81" at the breech & 1:36" at the muzzle
38" = 1:72" at the breech & 1:36" at the muzzle

He will gain twist rifle shorter barrels upon request, but doesn't think going shorter than 31" (Jaeger) makes sense.

31" = 1:67.5" at the breech & 1:36" at the muzzle

WadePatton · « **Reply #19 on:** July 09, 2021, 11:11:18 PM »

Quote from: DanL on May 26, 2021, 01:24:26 AM

Thanks for the replies. I will see what land-groove widths are out there for a .40 square rifling liner. Mr Hoyt will probably know.

DanL

Let Mr. Hoyt advise you on rate of twist. Barrel makers tend to be pretty adept at knowing what works best for whatever you want to do with your gun.

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Author Topic: .40 roundball barrel twist rate (Read 2394 times)