What is the bottom-end bullet weight with good accuracy for a 1:12 twist?

What is the top-end bullet weight with good accuracy for 1:14 twist?

I'd like to shoot 225-280 grains, but would like to try the 310-325 grains; and you can always find 200 grain in a pinch (and there are some fast loads).

I applied the Greenhill formula I have here and it goes like this

with a 1-16" twist the longest bullet you should shoot is 1.20"

with a 1-14" twist the longest bullet you should shoot is 1.37"

with a 1-12" twist the longest bullet you should shoot is 1.60"

Weight of bullet is not the criteria...it's length!

vapodog, you mean over all lenght right?
Or does the bearing surface also play a role in regard of stability / accuracy?

My 250 grs Nosler PT measure 1,27" oa with a bearing surface of approx 0,68"

My favourite bullet is the RN Woodleigh 250 grs, which is a stubby 1,13" oa and only 0,45" bearing surface.
Still the Woodleigh are by far the most accurate and devastating bullet in my 1:14 Shilen barrel.

I would love to try heavier bullets, but they are hard to come by in my neck of woods...

From JBM Ballistics....

http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

quote:

Calculates the Miller stability factor. This formula was derived by Don Miller and published in Precision Shooting. This formula is much better than the antiquated Greenhill's formula. Stability value should be in the range of 1.3 to 2.0 to ensure bullet stability. Don Miller and Dave Brennan (editor of Precision Shooting) have also been kind enough to let me host his stability paper on my exterior ballistics bibliograpy page. The paper is titled A New Rule for Estimating Rifling Twist An Aid to Choosing Bullets and Rifles.

http://www.jbmballistics.com/b...rs/calculators.shtml

quote:

Originally posted by Arild Iversen:
vapodog, you mean over all lenght right?
Or does the bearing surface also play a role in regard of stability / accuracy?

Yes....it's overall length...

Such things as bearing surface plays a role but seems to not be included in the formula nor is it found anywhere I've read.

Velocity is also a factor (in achieving a threshold of RPMs) but is not included in the formula I use....

The science of twist rate seems a bit wishy-washy....but it is what it is...

My Whelen has a 1-12 twist simply to avoid this issue....it'll shoot almost anything and I seriously don't believe I gave up much to get it over a 1-16" twist.

Theoretically it reasons that if one puts less energy into rotation then he should be able to harness more energy into velocity.....but in practice this is miniscule....Go with the faster twist!

quote:

the Miller stability factor. This formula was derived by Don Miller and published in Precision Shooting. This formula is much better than the antiquated Greenhill's formula.

I can easily believe this!

quote:

Originally posted by Austin Hunter:
I'd like to shoot 225-280 grains, but would like to try the 310-325 grains; and you can always find 200 grain in a pinch (and there are some fast loads).

You're going about this all wrong, given the span of bullet weights you want to shoot. Clearly you should be looking at a 9.3x62 with a 12" twist.

KB

I do not remember what twist rate my Whelen has, I just know that it loves to put 225 grain Barnes "X" flat base exactly where I wanty them everytime.

Already have a 9.3x57 (not 62); so wanted something different.

I have a sporterized 1917 that I want to rebore to a 35 whelen. Too much $$$ to make into a 416 Taylor or 458 Win mag, but want to put the rifle to good use.

quote:

Originally posted by vapodog:

quote:

Originally posted by Arild Iversen:
vapodog, you mean over all lenght right?
Or does the bearing surface also play a role in regard of stability / accuracy?

Yes....it's overall length...

Such things as bearing surface plays a role but seems to not be included in the formula nor is it found anywhere I've read.

Velocity is also a factor (in achieving a threshold of RPMs) but is not included in the formula I use....

The science of twist rate seems a bit wishy-washy....but it is what it is...

My Whelen has a 1-12 twist simply to avoid this issue....it'll shoot almost anything and I seriously don't believe I gave up much to get it over a 1-16" twist.

Theoretically it reasons that if one puts less energy into rotation then he should be able to harness more energy into velocity.....but in practice this is miniscule....Go with the faster twist!

So a 1:12 twist won't do whacky things to the shorter, lighter bullets?

My wife has a 35 Whelen (great caliber) made up from a Rem 721 action
with a 20 1/2 inch Hart match barrel, originaly in 358 Winchester, cut off for her size and rechambered. The Twist is 1 in 12.
It shoots Barnes 225 gr. TSX into one hole. It
also likes Woodleigh 250gr RN and 250 gr North Forks for heavy game. All under 1 MOA. Loaded to 2500 fps with RL#15. She has 11 one shot kills in Africa with this gun. We tried the 310 gr Woodies but
length gave us feeding problems (few actions are longer than a 721) Would like to try the Hornady 180 gr Single Shot Pistol Bullets for varmits. Loaded on the hot side they should just explode a varmit critter. Hopes this helps with your project.

Good Shooting

Tetonka
DRSS

I have a 35 Whelen IMP with a 1-16 twist and it will shoot 275 grain RNs fine. I've shot 250 grain boattails out of it also. The 1-12 and 1-14 will let you shoot a longer heavier bullet but you will lose some velocity by going to a faster twist. If you want to shoot cast bullets go with a 1-16.

Sam

quote:

Originally posted by Austin Hunter:

quote:

Originally posted by vapodog:

quote:

Originally posted by Arild Iversen:
vapodog, you mean over all lenght right?
Or does the bearing surface also play a role in regard of stability / accuracy?

Yes....it's overall length...

Such things as bearing surface plays a role but seems to not be included in the formula nor is it found anywhere I've read.

Velocity is also a factor (in achieving a threshold of RPMs) but is not included in the formula I use....

The science of twist rate seems a bit wishy-washy....but it is what it is...

My Whelen has a 1-12 twist simply to avoid this issue....it'll shoot almost anything and I seriously don't believe I gave up much to get it over a 1-16" twist.

Theoretically it reasons that if one puts less energy into rotation then he should be able to harness more energy into velocity.....but in practice this is miniscule....Go with the faster twist!

So a 1:12 twist won't do whacky things to the shorter, lighter bullets?

Nope....not at all....

Where one runs into trouble is when he's using very light jacketed varmint bullets such as in the use of the .224 calibers where velocities exceed 3500 FPS and instead of the usual 1-14" twist barrels used in the Swift and 22-250 he decides to run a 1-9" twist for VLD bullets.

Calculate the RPMs of a 4,000 FPS bullet at one rev per every nine inches....I've had bullets literally blow up in mid air...

One of the things often done by reloaders in their .35 Whelen is to use pistol bullets designed for the .357 Magnum.....and I'd back away from that using a fast pitch Whelen barrel as you might incur the same problem....I've never fired such bullets in my Whelen but would guess that if the velocity is kept under 3,000 FPS you'd still have no special problems....but this isn't what the Whelen is designed for....

quote:

Originally posted by Austin Hunter:
Already have a 9.3x57 (not 62); so wanted something different.

I have a sporterized 1917 that I want to rebore to a 35 whelen. Too much $$$ to make into a 416 Taylor or 458 Win mag, but want to put the rifle to good use.

A "rebore" means you keep the barrel (and its twist) which is probably 1:10.

My Whelen is a rebored Springfield with 1:10 and it will handle any bullet I care to put through it.

Barstooler

I wasn't aware that a rebored barrel had to have the same twist rate. Are you sure about that?

quote:

Originally posted by M Pursell:
I wasn't aware that a rebored barrel had to have the same twist rate. Are you sure about that?

I'd challenge that statement as well.

quote:

Originally posted by vapodog:

quote:

Originally posted by M Pursell:
I wasn't aware that a rebored barrel had to have the same twist rate. Are you sure about that?

I'd challenge that statement as well.

Me too.
Paul B.

quote:

Originally posted by Paul B:

quote:

Originally posted by vapodog:

quote:

Originally posted by M Pursell:
I wasn't aware that a rebored barrel had to have the same twist rate. Are you sure about that?

I'd challenge that statement as well.

Me too.
Paul B.

Yup, if that was the case Jim Dubell wouldn't cut and ream the existing bore out to a smoothbore and then rifle it with whatever number of grooves and twist rate you want.

You can pick WHATEVER TWIST RATE you like when you rebore...it doesn't have to be the original twist rate.

Doesn't really matter what formula you use, OPTIMUM twist rate is determined more from BULLET LENGTH, velocity and bullet diameter, plus whether or not it has a boat tail or a flat butt.

Take a look at any twist rate program...the ask for bullet diameter, bullet LENGTH, velocity and whether or not it has a boat tail...there are several freebees online...you can do your own calculations easy enough.

There is usually a range of twist rates or rather, a range of bullet lengths(which translates to bullet weight, which is why people get confused as to length vs weight) and velocities where one twist rate will work...AND...an OPTIMUM twist rate for a specific bullet length/velo...another place that gets people all messed up.

The OPTIMUM twist rate is the ratE at which a specific bullet length achieves the HIGHEST level of stability within a NARROW, specific range of velocities.

The easiest way to understand what twist rate is to read the definitions for the various forumulas...then just look at what is the "normal" twist rate for the caliber you're looking at and forget all the BS that usually goes along with this question.

Unless you are building a target rigfe to use a certain bullet within a narrow range of velocities, for the most part factory/published twist rates work great.

I've seen twist rates for the 35 Whelen from 1-10 to 1-16 so take your pick...if it were mine I would pick a 1-12 as this twist will stabilize all bullets up to 2" in length(no bullets that I know of this long in .358 cal) and 3500 fs(way faster than you can get in a 35 Whelen even with very light bullets)

OR make your own decision based on that bullet weights you expect to use for the game you expect to shoot.

As usual...no flame or diss intended...some folks take my "direct" way of speaking as politically incorrect or something of that sort.

Luck

Thanks!

Just a little clarification regards which twist rate you can have on a rebore. On a true rebore, yes, you can pick whatever twist you want because all of the rifling is removed before the new rifling is made.

In the old days, some folks referred to having their barrels rebored when what was actually done was that their barrel was "refreshed" or "freshed out".

That is, the land diameter was either not enlarged at all, or only enlarged enough that PART of the original rifling was removed. Then deeper grooves were cut.

Perfect examples of that once very common practice performed by many barrel makers and gunsmiths are found in the many rifles that Harry Pope refreshed from .32-40 Winchester to .33-40 Pope.

Obviously if some part of the original rifling lands is retained, so is part of the original grooves. Then the twist had to remain the same as the old grooves were deepened.

quote:

Originally posted by Paul B:

quote:

Originally posted by vapodog:

quote:

Originally posted by M Pursell:
I wasn't aware that a rebored barrel had to have the same twist rate. Are you sure about that?

I'd challenge that statement as well.

Me too.
Paul B.

I appologize. I was just going by what I was told by an old gunsmith in Cour d' Alene, Idaho close to 50 years ago. That was the way he did it and I just assumed.

But that is what you get for assuming on ARF.

Barstooler

quote:

Originally posted by Barstooler:

quote:

Originally posted by Paul B:

quote:

Originally posted by vapodog:

quote:

Originally posted by M Pursell:
I wasn't aware that a rebored barrel had to have the same twist rate. Are you sure about that?

I'd challenge that statement as well.

Me too.
Paul B.

I appologize. I was just going by what I was told by an old gunsmith in Cour d' Alene, Idaho close to 50 years ago. That was the way he did it and I just assumed.

But that is what you get for assuming on ARF.

Barstooler

I think the comment was correctly addressed above with the exception of the case where the rebore was so slight as to not clean up the previuous rifling with the new bore.