Author Topic: 40 cal twist rate (Read 2415 times)

bowkill · « **on:** February 23, 2019, 03:27:55 AM »

Which is better in a 40 cal 42 inch barrel? A 1-60 or 1-48 twist?

Dennis Glazener · « **Reply #1 on:** February 23, 2019, 04:19:30 AM »

It's my experience that the slower twist (1 in 60") will shoot round ball the best, usually will take more powder to shoot the tighter groups.
Dennis

David Rase · « **Reply #2 on:** February 23, 2019, 04:31:35 AM »

All the .40 calibers I have owned have had a 1-48 twist and they all shot very well. Never had one with a slower twist so I can't speak to that.
David

mtlonghunter · « **Reply #3 on:** February 23, 2019, 05:19:50 AM »

I have one with 1 in 40 twist that will shoot ragged one hole groups with only 30 grains of powder.

Hungry Horse · « **Reply #4 on:** February 23, 2019, 05:24:01 AM »

Most barrel makers of old agreed that certain calibers, with certain twists, were just naturally accurate. One of those was a .40 cal. With a 1 in 48” twist rate. This is not to say a different twist rate won’t shoot well. I think certain calibers/twist combinations are just naturally easier to get to shoot well. Bill Large at times refused to sell,or make barrels with a twist he didn’t believe in.

Hungry Horse

Huntschool · « **Reply #5 on:** February 23, 2019, 08:12:36 AM »

I ordered my .40 Golden Age Swamped barrel (bought from Getz back in the 70's) after talking with them for quite a bit at Friendship in 1:66. It was intended for RB with some powder.

In my observations the two best calibers out there were .40 and .54. Both could easily be made to shoot spot on with varied powder charges for the yardage desired. There was something about the ogive of both balls that led me to make that decision but, frankly, I dont remember what it was. My brain has melted a bit since then.

I can tell you that I have killed squirrels with a .54 with a low powder charge that just put a hole in em and have killed deer and elk with the same gun that shot clean through with good ball deformation at up to 150 yards.

As to the .40 mentioned above, the same was true save the elk. However with 90gr of 3fffg that .40 would shoot a round hole through a hardened disc coulter at near 100 yds. I killed some deer real dead with it. Not in IL cause its not legal here.

rick/pa · « **Reply #6 on:** February 23, 2019, 04:57:30 PM »

I have a .40 Douglas barrel from GAA that shoots very well. 1 in 48 twist with 7 lands and grooves. I believe Douglas made them special for Golden Age Arms.

Pukka Bundook · « **Reply #7 on:** February 23, 2019, 05:42:57 PM »

A smaller ball will be stable with a faster twist than a larger bore, in fact it Needs a faster twist.
I cut my .44 at 1 ~45" and it will shoot with a 45 gr charge or a double charge at 90 grs. (2F) so I am sure a .40 somewhere in the 1 ~45 - 1~ 48" will work.

All best,
R.

smokinbuck · « **Reply #8 on:** February 23, 2019, 07:05:12 PM »

I have .40 rifles in 1:48, 1:56 and both shoot very tight groups. I currently have a new Getz .40 with 1:66 that is for sale. All of them will shoot well if you find the best load.
Mark

Daryl · « **Reply #9 on:** February 23, 2019, 08:55:16 PM »

Quote from: David Rase on February 23, 2019, 04:31:35 AM

All the .40 calibers I have owned have had a 1-48 twist and they all shot very well. Never had one with a slower twist so I can't speak to that.
David

Ditto:

I will add to that, my 48" twist .40 was a Goodoien bl. with wide grooves, narrow lands. It mattered not if I used a .398" pure lead ball or .400" lead ball. They both shot the same and loaded quite easily
with the .0225"(10oz denim) patch and the .0235"(railroad mattress ticking) patches I used in it. Both of these balls would shoot into 1/2" at 50 yards, benched.

Note, that with a water based "lube" this rifle shot about identically with 3F or 2F and anything form 55gr. to 60gr. same accuracy, same poi and produced 1,770fps.

However, when using a really slippery lube - ie: LehighValley Lube, I had to increase the 3F charge to 65gr. and 2F charge to 75gr. to achieve THE SAME accuracy.

Note that the velocity for both of these powders was just almost identical - 2,240fps-2,260fps, yet with the slippery lube, the powder charge was 10gr. different.

However, the accuracy and point of impact WAS the same.

Would I have preferred a slower twist - in a word, NO! The 48" twist, with a slippery lube, already demanded i exceed 2,200fps - do you need more from a BP driven round ball?

A slower twist has the POTENTIAL to demand more powder yet.

On the other hand, many guys NEVER experiment. They pick a ball, patch material, powder charge, go with that & put up with mediocre accuracy (compared to what they could achieve

with their rifle).

jerrywh · « **Reply #10 on:** February 23, 2019, 09:07:01 PM »

Most accurate gun I ever had was a 40 cal. with 1:48 twist. From the bench it would shoot 2 balls through the same hole at 100 yds. Done it twice the same day. That's when I was young. 60 grains of fffg dupont.

smokinbuck · « **Reply #11 on:** February 23, 2019, 10:03:51 PM »

I'm finding that a little heavier charge, 70 grs FFFg, in my 1:56 Rayle barreled table gun works well. I believe the higher velocity creates lower trajectory and increases accuracy. In the Fall it shot a .724" group off the table at Friendship.
Mark

ron w · « **Reply #12 on:** February 23, 2019, 10:05:57 PM »

what's being missed here is the dynamic couple between twist rate and velocity. you can't make a blanket statement like "smaller calibers prefer "X" rate of twist", because it does not take into account the velocity the ball is being driven at. this axiom is what forces us to do load development. as you change powder charge, you change velocity. it is that change that finds the sweet spot for any given caliber to produce the best accuracy from hitting the dynamic couple that is right for the specific caliber and weight of projectile. change any one part and the dynamic couple is disturbed and accuracy will be affected.
one can only generalize about what caliber will like what twist. this preference is extrapolated from historic performance, but that is as far as it can be predicted,.....from there , you need to develop the load that drives the ball at a velocity that satisfies the twist of the rifling for any specific ball. once found, of course the trick is to maintain the ball weight as consistently as possible and the powder charge as consistent as possible to keep the ball in the velocity that couples dynamically, with the twist rate.

hanshi · « **Reply #13 on:** February 23, 2019, 10:34:04 PM »

My .40 has a GM barrel with a 1-48" twist. Accuracy is superb with powder charges from 30 grains of 3F to 60 grains of the same powder. This is the only .40 I've ever owned and so I can't comment on slower twists. This rifle has never hunted and has only been used as a target rifle. It would make a fine squirrel rifle and also a satisfactory deer rifle where legal.

As for large bores on squirrels, I shot a fox squirrel with a prb in a .58 a long time ago. I aimed for the neck and the ball made a tiny slit going and the same thing on exit. I only took a few squirrels with the rifle since I do prefer small guns for small game.

Dennis Glazener · « **Reply #14 on:** February 27, 2019, 11:22:04 PM »

The slow twist that I had that shot so well was a 45 cal which was either 1 in 70 or 72 inch twist. That thing would really shoot when you loaded it with 80 to censored grains of DuPont 3F. Will not print the stupid hot load I shot in it. Just say I was naive and had read Turner Kirkland's notes on not being able to blow up a barrel properly loaded with black powder. God protects babies and young fools

Dennis

ron w · « **Reply #15 on:** February 28, 2019, 05:31:45 PM »

from what I understand about ballistics. twist rate is more an issue with bullets than round balls. because a bullet has a CG and two moments of inertia, it needs to have a dynamic couple between the two moments, through the C/G, in order to fly without gyrating. it is the rate of spin that couples the two moments. a round ball,....has no moment of inertia, only a C/G, so rate of spin is not as critical. hence, there is usually a wide range of spin that will stabilize a given ball weight/diameter. I think much of the "preferred rates of spin" for the popular calibers are derived by what the barrel makers decided to give their barrels and as most of us are not involved with the ballistic aspect of barrel making, we simply train our thinking around what twist tares are available and think that they are the rates that must be used because the barrel makers make their barrels in those twist rates.
this leads me to wonder just how accurately our modern barrels duplicate the rates given to original barrels and whether the original makers did much experimenting to find a specific "ideal" rate for the different calibers they made. it was expensive and very labor intensive to make a barrel back then,.....how many barrels were made for the intention of developing the right twist rate for a given caliber,.....or did the makers try different rates as they made barrels and let the customers be their testers...….I wonder.

David Rase · « **Reply #16 on:** February 28, 2019, 06:40:29 PM »

I have a little .29 caliber squirrel rifle with a 1-72 twist. The load I worked up for it uses 45 grains of triple f powder and it is a tack driver all the way out to 100 yards.
David

WadePatton · « **Reply #17 on:** February 28, 2019, 08:46:22 PM »

Quote from: David Rase on February 28, 2019, 06:40:29 PM

I have a little .29 caliber squirrel rifle with a 1-72 twist. The load I worked up for it uses 45 grains of triple f powder and it is a tack driver all the way out to 100 yards.
David

Wow. My 30 is a 48" twist, but I trust the man who rifled it to give me a proper twist. My 40 is also 48".

When I get 'em into the wood and dressed out, I'll see how they shoots. But also I trust my ability to vary power charges enough to find what they prefer and to shoot to my notions of accuracy.

There certainly is a lot of complexity to twist rates when one considers the various projectile shapes and velocities utilized in all of guns (as I used to do). BUTT seeing how we mostly only consider round balls and BP these days I'm glad to let the bbl makers fret over twists and other rifling parameters--and I'll work on all the other stuff.

Daryl · « **Reply #18 on:** March 01, 2019, 06:24:48 AM »

As far as velocity and accuracy, my .40 shot well at 1,770fps and at 2,240fps to 2,260fps. That's 470fps difference and all due to the lube used.

bowkill · « **Reply #19 on:** March 01, 2019, 07:58:22 AM »

The reason I ask is because coleran is a 1/48 twist and green mountain is 1/66. Say they both will shoot well tho. Was thinking of green mountain..

ron w · « **Reply #20 on:** March 01, 2019, 04:25:28 PM »

a regular bullet ,...longer than caliber, needs specific rate of spin to stabilize because of it's length following a parabolic arch as it flies. a round ball has no length in comparison to it's caliber so there are no secondary moments trying to pull the C/G off it's intended path of fight and all that is necessary is to get it spinning decently in order to stabilize it. therefore, it will stabilize over a fairly wide range of twist rates. the biggest variable that affects how well it stabilizes is it's velocity, hence load development is all about finding the relative sweet spot in velocity that works best with the twist rate provided and because there is no dynamic couple (a C/G with a front and rear moment of inertia trying to make the bullet yaw in flight) with a round ball, that sweet spot can occur over a fairly wide range of twist rates.

WadePatton · « **Reply #21 on:** March 01, 2019, 08:10:45 PM »

Yup.

And then we've got the gain-twist options.

Also I think I'll never be quite able to grasp straight rifling. I mean, if you're going to cut grooves why not twist 'em? It's really really close to the same amount of work.

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Author Topic: 40 cal twist rate (Read 2415 times)

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