Twist rate, bullet size and velocity - Sweet spot?

[FatJackDurham]

I have noticed a lot of material mentions twist rate, bullet size and velocity. I was wondering then if there is a Perfect Match for a gun, or a sliding scale, when it comes to reloading?

I just started reloading and I am trying to find a sweet spot for loads. I need both a light load for cowboy shooting and I'd like a magnum load that will perform well out to 125 yards, which is were I seem to be loosing accuracy. I don't thing I will ever be able to shoot my Rossi 357 much further.

Recently, I had shot some factory FTX rounds and some Fiocchi Match rounds. Both kicked a lot harder that the rounds I have been reloading in similar sizes. I notice also that the velocity reported in the load manual is lower than on the sites. For example:

The Hornady FTX LEVERevolution bullets are listed as having a rifle muzzle velocity of 1850 FPS. The pistol velocity is 1440. However the reload data for .357 shows a top load of 1650 for rifle from the hornady page, and the hodgdon pistol data shows mosly 12s and 13s except for the H110 load with shows a high velocity but a curiously low pressure.

I tried loading some 125 grain XTP rounds at 19 grains of I4227 and shot a bunch this weekend with a scope, trying to see if anything I had available seemed more accurate.Nothing I loaded came close to the Fiocchi Match ammo I had shot. While talking to a range-er who was admiring my rifle, he asked with the twist rate was.

I had tried to measure it once, but it failed to make a full revolution with a cleaning rod, jag and patch. This must me it has a greater twist than the barrel lenght, right? So, I'll remeasure tonight, but I wanted to put the question out there.

If I have a twist rate of longer that 1:20, maybe as low as 1:30, what resources should I look at to try to match a bullet size and load to that? I can't remember where I read if a shorter round liked faster twist or vice versa......

Any conversation on this topic would be facinating.

[O.S.O.K.]

Yes, there is a sweet "range" for sure with bullet weight/bearing surface vs twist. And the bullets must fit the bore and take the spin as they go down the barrel...

Greener addressed this many moons ago and developed his formula for determining the best rifle twist for a given caliber/bullet weight.

Velocity also does affect this - boosting velocity seems to extend the "range" from what I've found.

This is the case with 44 Mag leverguns with 1:38 twist rates shooting 300+ grain bullets - the max velocity seems to be needed in order to get good enough stability to keep things together - but after a certain point (150 yards or so?) they begin to come apart.

For that caliber, 1:20 really is a much much better choice.

[COSteve]

Lighter (shorter) rounds for a caliber stabilize at lower twist rates while heavier (longer) rounds usually like higher twist rates. Consider the M16's 5.56 (.223). When first released, the M16 had a 1:14 twist which was later increased to 1:12 for the M193, 55grn bullet developed for it. However, as the Army went with heavier bullet weights like the M855, 62grn and MK 262, 77grn, they realized that they needed a faster twist to stabilize the longer, heavier bullets so they now produce the the M4 carbines with a 1:7 twist.

At one time Colt recommended to the DoD a 1/9 twist barrel as optimum to use both M193 55gr and M855 62gr ammunition. However, the 1-9 had trouble stabilizing the M856, 64grn tracer round due to the length of the projectile, so 1/7 was chosen, to stabilize the tracer round. That's why many commercial AR15s have 1:9 twist barrels, as they are likely to only shoot 55grn and 62grn ammo, however, it has been noted that the 1:9 twist is good for solid bullets weighing from about 50grns up to 69grns.

[retmech]

I have played with a couple Rossi's and a Winchester 94 in .357. The Sweet spot is dependent on bullet weight, profile and distance you want to shoot. The Rossi's are 1 in 30" twists and the Winchester is 1 in 16" twist. My experience as follows. With .38 spl wadcutter loads all 3 guns are accurate at 50 yds. At 100 yds the wadcutters tumble and go wild from the Rossi's, still flying point on from the Winchester. The Lee 158 rnfp at 1150 fps really accurate at 50 yds in all 3 guns, tumbles out of the Rossi's at 100 yds. Bump the speed up to 1500-1600 fps and it shoots ok out of the Rossi's at 100 yds. Lyman "Keith" 358429 (SWC) loaded to .38 level loads (1100 fps rifle) good only in 16" twist Winchester. Load the same bullet up with max load of 296/H110 which clocks 1600FPS+ and all 3 guns are accurate to 200 yds. For lower velocity plinking loads out of the Rossi's the Lee 125 RNFP is super accurate. I have shot a number of 10 shot 100 yd groups with that bullet that average between 2-2.5" and they hold that accuracy level to 200 yds. I load that bullet with 231 to 1200 fps, it's my centerfire .22!

[KirkD]

I agree with the above posters, especially with the concept of a sweet 'range'.

[FatJackDurham]

I found two formula's online. One shows the best twist for a bullet length, and in reverse, shows th largest bullet suitable for a particular twist.

The other takes velocity into account and also predicts the best twist for a bullet size, and conversly, can be twisted to show the best minimum velocity for a given twist rate and bullet size.

Of course, I'm sure this is only advisory, but I'll be interested to see the results.

retmech, your data is intriguing. I have not beenable to get within a 3 inch circle at 100 yards yet, except for using factory FTX and a scope.

[Griff]

The length of the bullet refers to the bearing length, not simply the distance from nose to base. So when folks speak (write) about the longer (heavier) bullets liking a faster twist than shorter (lighter) bullets, it's the bearing length that's important. So a tapered, pointed boat tail bullet might have a heavier weight than a blunt round nose, yet have a shorter bearing length, and might just like a slightly slower twist... especially if they're going really fast.

There's nothing overly simple about this reloading, huh?

[AJMD429]

I once made a spreadsheet with the available bullets in each caliber, and their calculated lengths (assuming some 'standard' ogive, etc.), and the required twist for given velocities.

The interesting thing was there seemed to be certain 'favored' calibers where excellent/efficient bullets were available in long-for-caliber (or 'heavy-for-caliber') sizes, and if rapid-twist barrels were available in that caliber, one could make a practical rifle shoot them.

Of course, if a nice long high-ballistic-coeffient bullet requires 200,000 rpm for stability, you have to either push it VERY fast through a 12" twist barrel, or at a moderate speed through a 6" twist one, so that determines the size case/power you need.

Anyway, the calibers with very good potential seemed to be .375, .338, .308, .243, and .223. Even .45 and .50 were pretty good. For whatever reason .44 (.430 or so) totally stinks, as does .35 (.357 or so) - bullets in those sizes are pretty much 'pistol' bullets, so even if you have a .358 BOSS Mag, unless you make your own bullets, you're limited.

I suppose some of it has to do with simple popularity, or which ones military uses.

Of course the OTHER factors in bullet selection include the performance of given bullets at given velocities. On paper, it's moot, but you don't want to shoot a critter with a bullet constructed for a much higher or lower velocity than you're actually using - the results can be inhumane.

[retmech]

retmech, your data is intriguing. I have not beenable to get within a 3 inch circle at 100 yards yet, except for using factory FTX and a scope.

For you cowboy low velocity shooting in the Rossi I would recommend the Lee 125 RNFP bullet or the Lee 9MM truncated cone bullet(120 gr 9MM). Both are very accurate in the Rossi's and feed very well. I have a 2X pistol scope on my 20" carbine for load development and the 24" octagon wears a tang sight, both will stay 3" or less with the Lee 125 bullet.

[FatJackDurham]

Okay, then. I'll order some Lee 125 and compare them the Hornady 140 cowboy rounds. Do you know the length of those bullets?

Griff, I wondered about the bearing length. I have read articles that confirm what you say, and also contradict it. For instance, here is an article that says that total length of the bullet is more important than bearing because of the relationship between center of gravity and center of pressure.

http://anarchangel.blogspot.com/2007/01 ... ology.html

That would explain why short bullets don't need to spin as fast, because their center of gravity is closer to the front of the bullet, and there would be less aerodynamic leverage to tilt during flight.

[Tycer]

For whatever reason .44 (.430 or so) totally stinks, as does .35 (.357 or so) - bullets in those sizes are pretty much 'pistol' bullets, so even if you have a .358 BOSS Mag, unless you make your own bullets, you're limited.

I question the 35 cal statement. I see at least 10 bullets in .358" from 225 to 345 grains on Midway alone and have molds from 210 to 300. The Whelen and 358 Win have been around long enough that heavy for caliber rifle rounds are available. For long bearing length, the Barnes 225 looks like a winner (expensive winner). I'll bet that bad boy could be pushed zippidy doodah.

[Tycer]

Regarding the OP, you could probably get the 180's to stabilize in the 1:30" Rossi, but they would most likely need to be 1800fps or better. Shoot some and see. Get a box of the Buffalo Bore. My guess is the 1:30" is what Rossi feels is best for the most common .38/.357 ammo bullet weights 125-158grain.

[COSteve]

The length of the bullet refers to the bearing length, not simply the distance from nose to base. So when folks speak (write) about the longer (heavier) bullets liking a faster twist than shorter (lighter) bullets, it's the bearing length that's important. So a tapered, pointed boat tail bullet might have a heavier weight than a blunt round nose, yet have a shorter bearing length, and might just like a slightly slower twist... especially if they're going really fast.

There's nothing overly simple about this reloading, huh?

I agree that bullet shape has an affect because of the bearing surface, however, in my example I was using similar bullet types (Spitzer) in my comparison as I took the OP's question to be one more of differing bullet weights of similar bullet types.

[preventec47]

no need to guess speculate or argue, go here and figure it
out with the twist rate calculator

http://www.realguns.com/calculators/riflingtwist.html

[retmech]

Bullet stability can't always be done on a calculator or just using length. With my Rossi's and their 30" twist two bullets in the 158 gr range are an example. The Lee 158 gr TLSWC is longer than the 158 gr RNFP but at 1150 fps it is accurate out to 200 yds (3-4 MOA) while the shorter 158 RNFP tumbles at 100 yds at the same velocity. What really surprised me was how accurate the short pistol bullets(120 and 125 gr) were at 200 yds. My initial thoughts were that they would not do well. Obviously you would not use them for hunting anything other than small game but for target work and ringing a 200 yd gong they work great!

[FatJackDurham]

Bullet stability can't always be done on a calculator or just using length. With my Rossi's and their 30" twist two bullets in the 158 gr range are an example. The Lee 158 gr TLSWC is longer than the 158 gr RNFP but at 1150 fps it is accurate out to 200 yds (3-4 MOA) while the shorter 158 RNFP tumbles at 100 yds at the same velocity. What really surprised me was how accurate the short pistol bullets(120 and 125 gr) were at 200 yds. My initial thoughts were that they would not do well. Obviously you would not use them for hunting anything other than small game but for target work and ringing a 200 yd gong they work great!

Retmech, I love your specific details.

As it happens, one shoot I hope to do is the Buffalo Shoot at Dalton NH, which has a 250 yard gong. I had thought I'd need a heavy bullet, but now, I think I should go with a light bullet. It still has to be less than 1400 FPS. I am definitely getting a chrono and some of those 125 lees.

[AJMD429]

I see at least 10 bullets in .358" from 225 to 345 grains on Midway alone and have molds from 210 to 300.

Wow - I'd never seen any jacketed ones over 225 grains. It was a few years ago when I was infatuated with the .358 BOS Mag (which gets the 225 grain bullet to 3700 fps, but was considering the possibilities of a heavier, slower projectile), but I realized I had no practical use for such an animal, so never pursued the matter. If my .35 Remington can't do the job, it's probably something I shouldn't be shooting at anyway.

[FatJackDurham]

What is the twist rate of the Uberti Cattleman .357 with a 5 1/2 inch barrel? The catalog says "RIGHT".

I looked down the barrel and one groove starts at the bottom and ends on the side, about a quarter turn for the length. That would be about 1:20. Does that sound right?

[FatJackDurham]

Although, I suppose thefirst inch and a half is the chamber, so it's probably 4 inches of rifling: 1:16.

[John Boy]

Fat Jack - Scroll down this thread until you reach the posts related to the Powley Calculators. Upload both and do you calculations
http://www.assra.com/cgi-bin/yabb/YaBB. ... 650751/9#9
The starting factor is - you have to know the twist ratio of your firearms

Also, the twist ratio and bore/grove diameters are on the Cimarron website
http://www.cimarron-firearms.com/boregr ... Uberti.htm

[FatJackDurham]

Thanks John boy! I looked and didnt see that.

.355 grooves? Hmm. I'll slug mine and verify that. Seems a little tight.

[FatJackDurham]

Sigh. I slugged my revolver.

Lands: .347
Grooves: .355

...

Cylinder Throat: .359

.359 is an aweful lot of space around the bullet as it travels to the barrel.

Thoughts?

[retmech]

You want .359 bullets, or at least .358 and NOT hard cast if you're talking cowboy loads! I'm speaking to lead bullets here.

[FatJackDurham]

Theoretically speaking, shouldn't the chamber throat be the same size as the bullet, or .001 smaller? and Shouldn't the groove diameter be not more than .002 smaller than that?

Since I can't reduce the size of the chamber, should I have my barrel opened up to .357 groves and .350 lands? Then, I could shoot .358 and .359 lead hard cast through it. As well, my Rossi bore is a minimum of .357, so the bullets should work well in both guns with a minumum of deformity.

Or is it not advisable to try to rework a bore that way? Would it be cheaper to try to find the right size cylinder?

[Terry Murbach]

Sigh. I slugged my revolver.

Lands: .347
Grooves: .355

...

Cylinder Throat: .359

.359 is an aweful lot of space around the bullet as it travels to the barrel.

Thoughts?

YOUR THOUGHTS ON THIS ARE ENTIRELY BASSACKWARDS HERE !! A .359"O.D. BULLET IS AN EXTREMELY TIGHT---TIGHT!!!---FIT IN A .355"I.D GROOVE. THIS IS A GOOD THING.
YOU HAVE ALSO ALMOST ENTIRELY OVERTHOUGHT THIS ENTIRE SCENARIO AS YOU POSTED IT HERE.
IT IS NOT ROCKET SCIENCE .
THERE IS REALLY NO "SWEET SPOT" PERSE. NONE !!
THERE ARE AREAS AND TWIST RATES THAT TEND TO WORK BEST WITH SOME PROJECTILES AT CERTAIN VELOCITIES. YOU CANNOT PREDICT THIS.
NO ONE CAN DO YOU WORK FOR YOU.
YOU MUST TEST THE LOADS IN YOUR GUNS ON TARGET AND OVER THE CHRONOGRAPH SCREENS.
DO NOT WANNA CHRONOGRAPH; TOO CHEAP TO BUY A CHRONOGRAPH? YOU'RE SIMPLY WHISTLING IN THE DARK
ALL GUNS AND ALL BULLETS TEND TO ALWAYS SHOOT FLATTER THAN ANY OF THOSE SILLYAZZED CHARTS SHOW.
AND SO IT GOES....

[FatJackDurham]

Maybe I'm not clear. I Want a chrony and will get one. My question is that the throat is too wide in th cylinder. A .357 or .358 bullet will not be guided into the barrel. If I use a .359, won't it be likely to lead and spray out the gap?

In chicories book and another reference I read, they talk about the cylinder those matching the bullet, and the grooves only being slightly less than the bullet.

Reading you post, it seems like you think I thought the .359 bullet would be loose in the barrel and the I don't want to buy a chrony. The opposite is true.

[retmech]

The general rule is you size to the throats in a revolver. You are fortunate in that your throats are bigger than your groove. That said it is no problem to be .003-.004 over groove size with lead bullets. I own a Ruger Super blackhawk .44 mag with .434 throats and .429 groove. I shoot .433 bullets with excellent accuracy and zero leading up to 1400 fps out of that gun. For your cowboy loads you would do just well with soft lead bullets at .358. They will swage down just fine in your barrel and should not be a problem. In the long range magnum category you will have to spend some time at the range and work that out between you and your gun. I've spent the past couple years playing with three .357 lever guns, two Rossi's and a Winchester 94. I can average 3MOA out to 200 yds with cast bullets at 1100-1200 fps and 3-4MOA at 1600 fps with plain base cast bullets out of all three guns. A lot of powder and lead went downrange in the process. Good luck to you and If you want to learn more about lead bullets here is the place to go. http://castboolits.gunloads.com/

[FatJackDurham]

Okay then. It's payday, so I need to go order some bullets and a chrono.