revolver barrel twist

[felix]

Again, folks, they are talking NO FREEBORE! ... felix

[44man]

Again, folks, they are talking NO FREEBORE! ... felix

Glad you said that but it would still be a good read to see what changes are being made.
Might be something to debunk!

[StarMetal]

The reason, Joe, is accelerating the boolit's rotation. Wider projectiles are progressively harder to do without stripping. ... felix

Felix and all,

Here's the answer I got back from my friend at Lothar Walther:

None of those barrels we did had gain twist. Not even all the ones they did had it. Marketing hype and truth are mutually exclusive. A .452 dia. bullet spins in a revolver barrel just the same way a 32 357 or 44 does. The barrels groove was 450 and the bullet was 452 so the grip was very strong. This is what led to the super high hydraulic deformation inside the barrel.

I'm a little confused by it, the part on a 450 groove and using a 452 bullet. Yeah I know he said for a tighter grip. Now a friend of mine has a 460 Smith and if I recall he said his has normal rifling. I just emailed him to find out for sure.

Joe

[44man]

Felix and all,

Here's the answer I got back from my friend at Lothar Walther:

None of those barrels we did had gain twist. Not even all the ones they did had it. Marketing hype and truth are mutually exclusive. A .452 dia. bullet spins in a revolver barrel just the same way a 32 357 or 44 does. The barrels groove was 450 and the bullet was 452 so the grip was very strong. This is what led to the super high hydraulic deformation inside the barrel.

I'm a little confused by it, the part on a 450 groove and using a 452 bullet. Yeah I know he said for a tighter grip. Now a friend of mine has a 460 Smith and if I recall he said his has normal rifling. I just emailed him to find out for sure.

Joe

Just go to the S&W site, it tells you in black and white that the .460 has a gain twist.

[felix]

Nothing wrong with gain twist, as long as it is extremely slight and used primarily for keeping constant tension on the groove cutter. Just what is the difference between initiation and termination on that 460 barrel? ... felix

[StarMetal]

Just go to the S&W site, it tells you in black and white that the .460 has a gain twist.

Here's what he said about that Felix: Marketing hype and truth are mutually exclusive.

Joe

[alamogunr]

Fraid not! The website for Precision Shooting only has the feature article for the three most recent issues. The magazine is fairly specialized toward bench rest shooting. I have subscribed to it for several years because of the odd ball articles they include each month. For example, the June,2009 issue has an article titled "Shooting the Grease Gun", featuring the WWII stamped sheet metal submachine gun.

If I can find someone that has a scanner, I will try to get a copy for you.
John
W.TN

This in reply to 44 Man's query about a link.

[felix]

That, of course, Joe, depends on the folks doing either. Some salemen talk about attributes that have no effect on the application on hand, and some engineers talk about the superiority of their equipment in making the said product. All what we want on this board are guns WE can shoot using the cheapest components we can purchase or make. Completely different goals than the BR application, where cost and effort together is of no concern. ... felix

[Bass Ackward]

The real thing to take away with cast usage is the the faster the twist rate that you "have to" use because of choices you make in the launching system whether that be handgun or rifle, the narrower the accuracy window is going to be. ESPECIALLY if you want to push the envelope.

And from that, the narrower the options available to the reloader to work to fall within that window. That means everything from bullet weight, to design, to lube, to hardness, to everything.

Anyone that has ever fooled with cast very long learns very quickly that multiple reloading options makes for more accuracy choices .... and a more fun project.

[44man]

The real thing to take away with cast usage is the the faster the twist rate that you "have to" use because of choices you make in the launching system whether that be handgun or rifle, the narrower the accuracy window is going to be. ESPECIALLY if you want to push the envelope.

And from that, the narrower the options available to the reloader to work to fall within that window. That means everything from bullet weight, to design, to lube, to hardness, to everything.

Anyone that has ever fooled with cast very long learns very quickly that multiple reloading options makes for more accuracy choices .... and a more fun project.

I have not found that true in the revolver. A faster twist will DOUBLE boolit choice and weights I can use. Only the lighter boolits will not perform. Too slow of a twist severely limits boolit choice and you can be stuck with light for caliber boolits. Of course the gun will still "go bang" with whatever you put in it.
You have to determine what accuracy is of course. Take My .475 with a 350 gr boolit. It will do 2" to 3" at 50 yards and most guys would be tickled pink. Many jump up and down and wave their arms with 2" at 25 yards!
With a slower twist of 1 in 18" it gets very, very hard to get super accuracy as you pass 400 gr boolits, some have done it but not many. Most use over loads to do it. This twist loves 350 gr and will do 1" or less.
Mine does not start to shoot until I reach 400 gr and from there to 460 gr, it will hold sub 1" at 50 yards. It might even do it with heavier boolits but I don't have any to try.
I spent half my life shooting long range rifles with jacketed bullets and in every case, a faster twist was easier to work with but if I shot only to 100 yards or only used light bullets I would want a slower twist.
Twist rate still has to be determined by the use and distance you want your gun for. You can't say a slower twist is better anymore then I can say a faster one is better because everyone is doing something different.
But you can't ignore the importance of twist depending on usage.
For what I do, I want a faster twist. A slow twist might be perfect for you. You can't apply what you do for a fella that wants to shoot a heavy boolit for hunting and I can't apply what I do for a fella that wants a light boolit target load.

[jandbn]

Can anybody else chime in with their experience either similar or opposite of to 44Man's last post? I need more to stuff into the gray matter.

Suppose you were chambering a .44 Spl round in your Ruger SBH, and the characteristics of that .44 spl round were such that the bullet length was 0.790" --like the 250 gr. RCBS Keith bullet in my hand right now-- and the velocity was a typical old school .44 spl velocity of about 750 fps. Plug those numbers into this Greenhill calculator...

http://kwk.us/twist.html

...and see what pops out. While you're there, scroll down and read the bit about velocity: If you have to adjust the "constant" from 150 to 180 to compensate for really fast velocities, it makes sense that you would have to lower it for slower ones. This formula does that.

[edit] Here's another one that validates the 1:20 SBH twist. Again, consider our .44 Spl loaded with a Keith bullet to 750 fps...

http://www.uslink.net/~tom1/index.htm (click on "Calculate Optimum Twist Rate" and scroll down.)

SuperMag,

I guess maybe I am guilty of not delving deep enough into optimum bullets for a given twist rate. Your examples provided data for me to try in the formulas that I didn't consider. In my first post, I had used heavy for caliber boolits in the calculations. As I mentioned before, I will take all the knowledge and experience here any day rather than rely on calculations. But… I do have this “problem” of not leaving well enough alone. So I proceeded to take a closer look at the formulas.

After crunching numbers and pondering the use of “adjusting the constant”, my initial assumption (NOT conclusion) is that manufacturers are using twist rates to “cover all the bases”. What I mean is they use twist rates to stabilize worst-case load combinations. Others have said this in so many words, but I guess I’m deaf in one ear and can’t hear with the other. Based on my assumption, then longer boolits and more velocity means “over-stabilization”.

The long barrel bench rest folks are concerned with their twist rates in that they “want” the minimum twist needed to stabilize their chosen bullet. From what I can gather so for with practical handgun hunting/shooting distances, over-stabilizing the boolit has minimal affect that probably can’t be measured. My idea of the effective hunting range of a revolver is around 50 yards. My choice of a 45 Colt at 1200 fps is all I need and probably then some for hunting where I do and thus the reasoning behind that combination. I don’t pretend to know what difference over-stabilization in a handgun has in small bore to large bore and in between, but I think it would be a moot point. (44Man may disagree with over-stabilization as he shoots his revolvers for accuracy. At my age, I’d almost give my left nut to be able to shoot groups 44Man has posted.)

My quest now is for self-information. I would like to see a graph or pivot table that would plot minimum stabilization. I am not a mathematician by any stretch, nor do I understand gyroscopic science like benchrest crowd. What I do understand is a given handgun with a specific twist shooting a boolit of a specific length (and weight), must exit the barrel at a specific diameter where velocity can be measured by a chronograph. Now if I could just plot RPM for length and caliber. If I can accomplish that, it might give a visual as to any correlation. It wouldn’t be much use in real world application but I would get the satisfaction of doing it because I can (I hope).

Below is an illustration for those that may read this thread and have not considered a twist formula, is a comparison of your first example load and a heavy for caliber load. I used the twist calculator on http://kwk.us/twist.html. Miller’s Twist Calculator gives very similar results. (Maximum Specific Gravity (SG) value is 11.3 for lead. I used 11.2 as an arbitrary number for a lighter lead alloy boolits.) This comparison will illustrate what happens in regards to over-stabilization as velocity (RPM) is increased. (I am not picking on Ruger at all. It is just that twist is readily available on their website.)

44 Special (Ruger with 20 twist)
Weight: 250 grain
Length: .760”
Diameter exiting Muzzle: .429”
Velocity: 750 fps
SG: 11.2
Calculated Twist 24 (SG of 10.9 for J-word = 23)

44 Mag (Ruger with 20 twist)
Weight: 250 grain
Length: .760”
Diameter exiting Muzzle: .429”
Velocity: 1500 fps (your load in your SBH)
SG: 11.2
Calculated Twist 33
---------------------------------------------------
Other comparisons:

38 Special (Ruger with 18 ¾ twist)
Weight: 158 grain
Length: .630”
Diameter exiting Muzzle: .356”
Velocity: 750 fps
Length: .630”
SG: 11.2
Calculated Twist 19.5

357 Mag (Ruger with 18 ¾ twist)
Weight: 158 grain
Length: .630”
Diameter exiting Muzzle: .356”
Velocity: 1250 fps
SG: 11.2
Calculated Twist 25
---------------------------------------------------
45 Colt (Ruger with 16 twist)
Weight: 260 grain
Length: .670”
Diameter exiting Muzzle: .451”
Velocity: 750 fps
SG: 11.2
Calculated Twist 29

45 Colt (Ruger with 16 twist)
Weight: 260 grain
Length: .670”
Diameter exiting Muzzle: .451”
Velocity: 1200 fps
SG: 11.2
Calculated Twist 37
---------------------------------------------------

[gunsbrad]

Folks, this is a very worthy discussion and I just want to add this.

Benchrest some bench rest shooters are worried about overstabilization and try to get a minimum twist to shoot at the given range. For instance .22 rimfire 50 yard benchrest competitors are only concerned with accuracy at 50yds. They don't care if it destabilizes at 75 or 100. 50 yds is where the trophy is. I personally want my .22s to be accurate much farther, but I play a different game. All br shooters don't buy into the minimum stabilization theory.

Greenhill's formula was an attempt to give an easy to find minimum twist, not optimum. He never claimed it was optimum.

Brad Hurt

[jandbn]

Brad,

I guess I should have been more specific in my comments about bench rest shooters. I should have said "some", not imply ALL. You are correct about the Greenhill formula. My original thought was to "find" optimum weight with a known twist. All things considered, RPM seems to be the place to start looking and build off of that.

[felix]

Really, you can say "ALL", Jan. One deviates in that sport for experimentation only, such as for improvement in say, certain ambient conditions such as shooting through severe gusts. I can remember "unique" barrels were used for certain benches at certain matches by a few diehards. If these folks won consistently enough, everyone would switch to that configuration within a year or two for all matches. ... felix

[jandbn]

Felix,

I appoligize if I don't have my "poop in a group." I am still playing catch-up from 20+ years of being away from shooting and hunting. When I was shooting and hunting way back when, all I knew was more ft lbs and velocity was better. Now that I am some what older and wiser and have boned up a little on real world experience from others, I know I have quite a learning curve to overcome. My hope in posting was to get opinions/help from everyone which in turn, helps to "re-educate" me properly. I am sure I WILL make mistakes here and there, but unlike other forums, the vast majority of CB members are congenial folks that are willing to help rather than ridicule. There are many on CB that have my respect and I hope to learn more from the experience here.

[Lloyd Smale]

I can relate my loading experinces with 45 colt rugers to what 44man said, It never made sense to me that they went with a faster twist (1-16) then they did with the 44s. I know they were meant to shoot bullets realitivly slow but so is the 44 specail and they get a 1-20 twist. It is nie on impossible to find a bullet under 280 grain that will shoot well at long distantances in a ruger 45 colt. It cant be that the bullet doesnt get enough spin as the twist is faster. It has to be a matter spinning those bullets to fast. A combination of that and if you look closely at your 45 ruger the rifling lands and groves are even shapped a bit differntly then there barrels in 44 and are a bit shallower. Im sure what happens is bullets are spun so fast that they are stripping through the rifling to some extend. Im sure someone will jump in and say there 45 shoots well. For one thing im talking long range. Over 200 yards. Ive got some decent groups at 25 and 50 with them but even then a good load seems about 10 times harder to find for a ruger 45 then a ruger 44. I cant for the life of me figure why ruger does this. Again i guess its because theres for the most part a bunch of yuppy bean counters running most of these gun manufactures these days and for the most part we are an exception not the rule. Most people are happy shooting a box of factory ammo once or twice a year and are happy if they can hit a coffee can at 10 paces.

I have not found that true in the revolver. A faster twist will DOUBLE boolit choice and weights I can use. Only the lighter boolits will not perform. Too slow of a twist severely limits boolit choice and you can be stuck with light for caliber boolits. Of course the gun will still "go bang" with whatever you put in it.
You have to determine what accuracy is of course. Take My .475 with a 350 gr boolit. It will do 2" to 3" at 50 yards and most guys would be tickled pink. Many jump up and down and wave their arms with 2" at 25 yards!
With a slower twist of 1 in 18" it gets very, very hard to get super accuracy as you pass 400 gr boolits, some have done it but not many. Most use over loads to do it. This twist loves 350 gr and will do 1" or less.
Mine does not start to shoot until I reach 400 gr and from there to 460 gr, it will hold sub 1" at 50 yards. It might even do it with heavier boolits but I don't have any to try.
I spent half my life shooting long range rifles with jacketed bullets and in every case, a faster twist was easier to work with but if I shot only to 100 yards or only used light bullets I would want a slower twist.
Twist rate still has to be determined by the use and distance you want your gun for. You can't say a slower twist is better anymore then I can say a faster one is better because everyone is doing something different.
But you can't ignore the importance of twist depending on usage.
For what I do, I want a faster twist. A slow twist might be perfect for you. You can't apply what you do for a fella that wants to shoot a heavy boolit for hunting and I can't apply what I do for a fella that wants a light boolit target load.

[44man]

Lloyd, I suppose the .45 would do well with a 1 in 20" and would probably work better with lighter boolits because they are short for diameter. I sure would not go slower though.
On the other side of the coin is my Lyman boolit that gets rifling engraved almost to the meplat. Depending on alloy it drops from 343 to 347 gr. It can't be driven fast, doing 1167 fps at the most accurate point. This benefits from the faster twist because of the lower velocity and does not skid the rifling beyond a tiny bit at the front. This boolit is .855" long and is engraved about .750".
I have killed deer in their tracks to just beyond 100 yards and on occasion have shot 1" groups at 75 yards.
Since it is a Vaquero, the sights beat me for long range and boolit drop is out of sight so I have not shot it as far as my other revolvers.
The point is that the gun does exactly what I want it to. Anyway, it is back to what you want to do and you are correct that a little slower twist will work better for a lighter boolit.
Now I do have the 255 gr Lee and with a light load of 7 gr of Unique, it is a can buster supreme out to 50 yards. I never tried to take it to a heavy load of slow powder because I hunt with the heavier boolits but I don't think it would do so good. I feel Ruger rifled it for normal Colt pressures with factory loads. Lighter boolits shot slow should benefit from the faster twist but if you want to jack them up you need a little slower.
Actually, the faster twist should be ideal for a cowboy action shooter with those zero recoil loads. It is the only way to get some spin on them. If you want to hunt, just use a heavy boolit, the LBT 335 gr shoots super too.
Now Jandbn shows calculated twist rates and I can assure you, none will work. If you found something to shoot, it will be the ONLY thing you can shoot. After two or three years testing you would finally give up.

[felix]

Lloyd, the 45 surely can gain stability if they got rid of those shallow lands. ... felix

[felix]

Jan, no apology needed for anything. The BR crowd is interested in only one thing and that is how well they can shoot under extreme stress (weather, mainly). The guns have little to do with it because they are the "same" except for maybe personal balance in the recoil arena. Many different stock differences, for example. ... felix

[44man]

Felix, doesn't look that bad!