Twist Rate in Modern Gunz and Black Magic

[Cemetery]

Another thread shot ta he!!. Nothin left ta discuss here. Cemetary can ya come up with somthin else we can beat around?  WM

Here's a new topic to beat around........

What's the deal with modern twist rates in rifles and black magic? 

I ask this because I noticed that the twist rate in my original '73 in 44.40 is less than my modern Burgess clone in 44.40, I told it's because this twist rate is made for modern ammo.  But how does this affect black powder loads?

[zymurgeist]

From what little I've read as long as the bullet is moving at sufficient speed the bullet mass and length determines ideal twist rate. It's an interesting question.

Here's a link to a formula. Probably not the last word but a good place to start looking.

Here's a link to where it gets completely over my head.

[Sir Charles deMouton-Black]

I am not a scientist or mathematician, but I read a bit, then forget where I read it, as If I feel like it, I can look it up again.  Like anyone can with more than a few idle moments to waste.

http://en.wikipedia.org/wiki/Alfred_George_Greenhill

Greenhill is not mentioned in Pollards History of Firearms, nor by Greener in The Story of the Gun. Versions of the Greenhill Formula can be found on the net for all to use on a plug in the data basis.

With roundball muzzle loaders a slow twist was all it took to calm the erratic lobbing of a smoothbore. When elongated bullets were developed they discovered that the twist had to be tightened up to keep that 'ol Pickett ball pointy end first.  A tighter twist must be harder to do well, but someone must have tried and got poor results and blamed it on "stripping" or skipping, the rifling. More gradual rifling also seems to allow greater velocity.  When the Express rifle was being adopted twist rates slowed down somewhat.  That is what was going on when Winchester adopted lighter-for-bore ammunition like the old '73. Taken at its extreme, slow twist lead to no twist in some ultra high velocity smoothbore tank cannon of the modern day.

Science is often a slow process of trying ideas out to see what happens, the Emperical method.  Variations in twist sometimes reflect icompeting ideas that take time to resolve.

Not well researched, but the above is how I simplify the issue.  So, now the real experts can ring in! Perhaps we will eventually see a CAD diagram? Or a 30 shot firing test?

[john boy]

Who is making a replica 1883 Burgess rifle in 44-40?  Would like to see the website.
Next, what is the twist of a '73 and '83, if such a replica is being made in 44-40?

[Cemetery]

Who is making a replica 1883 Burgess rifle in 44-40?  Would like to see the website.
Next, what is the twist of a '73 and '83, if such a replica is being made in 44-40?

Got mine from Taylor's  http://www.taylorsfirearmsstore.com/1883_burgess.htm the 20" carbine, smokes real good 

JB, I was cleaning it a few weeks ago, and noticed how the twist rate differs from my Winny '73 made in 1893.  Asked Quaker Kid about this, and he said it was simply cause the Burgess was made for modern smokeless ammo.

So got me thinking, if modern smokeless ammo has higher velocity, and needs a higher twist rate, how would a slow moving boolit built on real black react to this rifling in the long run, thing cowboy distances don't matter much......

Makes me wonder about original 73's, when they switch to all smokeless, did they alter the twist rate at any point?

[john boy]

Thanks Cemetery, I thought Uberti was the only one making the 1883's and their website lists only 45 Colts.
Quaker Kid knows his stuff and is probably right.  I don't know the twists of either your '73 or '83.  Do you know the twist ratios of each?  If not, a tight patch and a cleaning rod will determine what they are.

OK, what makes a bullet shoot, whether its BP or nitro in a given twist?  It's the stability factor of the bullet, it's dimensions and the velocity being shot ... whether with BP or smokeless powder. Have to remember, firearms are DUMB.  They really don't know what type of powder is pushing the bullet down the bore

Crank in the the values for your reloads and see what the Greenhill formula has to say.  Better yet, use the stability calculation program on JBM Ballistics ... http://www.jbmballistics.com/ballistics/calculators/calculators.shtml
The best stability program is the Powley Stability Calculator but it is no longer on the Canadian website

[Sir Charles deMouton-Black]

Here is one basic calculator. 

http://www.z-hat.com/twistrate.htm

I like this one better;

http://kwk.us/twist.html

[Dick Dastardly]

Just an esoteric observation.  I shoot 44ELR (Extra Long Russian aka 44 Magnum) in my RVs and B92.  Mav Dutchman bullets stabilize nicely.  Since I shoot only Holy Black for my SASS discipline, I am prepared to state that "modern" twist guns will handle Genuine Powder ammo just fine.  The only qualifier I'd add is that you need a bullet that hauls enough lube to keep yer guns running trouble free for Ten + stages.  Big Lube®LLC bullets have been well proven to do this.

DD-DLoS

[Mako]

Cemetery,
Sir Charles ultimately has the answer, he just wasn't taking credit for it.

The originals were made to shoot lead bullets with relatively deep grove rifling at a rate which would stabilize the bullet but not allow the bullet to strip or twist in the bore because of the relatively soft lead.  As Sir Charles said there is the potential for stripping of the lead so there is a limit to what can be done with a tight twist rate and a long lead projectile.  He's also right about the work of AG Greenhill in developing the theory and a basic method of matching twist rates with projectiles based on the factors listed in his formulas.  But even with his basic formula or more advanced forms dealing with centripetal stabilization you can't always "get there from here."

Rifling and lead bullets has been a topic of discussion ever since new forms of rifling  higher velocities, smokeless propellants and bullet jackets or driving bands became common.  Even before Marlin introduced the microgroove rifling there was already a change in rifling depth for firearms that were intended to shoot jacketed bullets.  Marlin still continued to produce a traditional rifling form they called "Ballard Rifling" for use with higher velocities and lead bullets.  With increased velocities came increased pressures, with modern propellants came higher pressures.  Barrel and frame materials were able to keep (to some extent) up by using stronger and more homogenous steels, but the lowly bullet was stuck with the materials of choice being lead, lead alloys or lead covered with a cupronickel or later guilding metal jacket.  

With the move to semi-smokeless and smokeless powders the bores did not foul as quickly from the powder residue as had been the case with Black Powder.  Some of the depth of the older rifling was to assure a barrel wouldn't "foul out" during use.  From a manufacturing standpoint this was a process improvement and major savings in time if they could move totally away  from single point cut rifling to broached, or button rifling (now there are several other forms as well).  Both were normally (but not always) shallower than the single point cut or "hook" rifling.

Long bullets have a definite ballistic advantage but raise havoc in the barrels themselves.  There is increased pressure, friction and erosion caused by faster twist rates.  Anyone familiar with the ongoing debates about rifling and the match bullets or even the SS109 or M855 ball bullets for the 5.56 cartridge know there is a departure from the current military twist rate of 1:7 in the twist to a 1:9 being the favored twist for accuracy, longevity and pressure with commercial or match barrels.  The 1:7 twist is a worst case twist prescribed to assure the penetrator of a 62gr "longer bullet" on the standard NATO "steel helmet" test at 600 meters (actually it was the M856 (NATO FN L110) "long" tracer round that has the biggest problem).  This twist is actually for the worst case environmental conditions which is arctic conditions low altitude dense very cold air.  There are two factors at play there, the air density and the lower energy of the propellant in low temperatures which decreases muzzle velocity.  

Many people choose 1:9 if they won't shoot anything longer than a M855 (a Sierra 69 gr is on the edge) or those who just can't decide choose 1:8. People forget that almost all military barrels now have hard chrome chambers and bores to resist erosion, most match quality barrels are stainless steel and they ten to be 1:8 twist which is partially due to the increased wear of the higher twist. They reason they won't be shooting the long tracers

The downside to the 1:7 twist with the heavier bullets is that the pressures for M193 ball was 52,000 psi at the "normalized" environmental conditions with a muzzle velocity of 3,250 fps out of a 20 inch barrel 1:12 twist, the M855 ball is 55,000 psi at 3,025 fps out of a 20 inch barrel and the 1:7 twist.  They jacked the pressures up to be able to say they were making 3,000 fps.  There is increased barrel and throat erosion and the brass is stretched more.  This also makes the carbine length gas systems an extractor "breaker" since the port pressure is in the 30KPSI range at that length. Then when you put them in a 14.5" M4 the M855 has a sad little bullet going way too slow (but it's spinning like a Dervish) trying to hit the bad guys are on the other side of the canyon.  2,700 fps is the magic thresh hold for M193 and M855 effectiveness.

Twist can be too much of a good thing.  Then there is the argument about "overstabilization" of the projectiles... we'll stay out of that.

Back to the old barrels, they were soft, they wore easily and the chambers couldn't take high pressures.  Long bullets weren't de rigueur in the day partially because of the diameters and the weight a long projectile would end up being.  There was a lot of experimentation with gain twist rifling.  This allowed the bullet to start out with a slower twist rate and not strip the rifling as it spun up to speed moving down the barrel.   This was more expensive to manufacture so it was often abandoned after a short period of production.

In the 19th century the rifling "erred" on the side of a cautious slow twist to avoid pressure problems and to avoid these problems with the iron receivers and just better than iron mild steel barrels.  My Winchester '73 in .44WCF (1886) has a RH 1:38 twist.  One other little tidbit for you, the Mod. '94 was produced in .30-30 with a 1:12 twist, my first rifle was a family gun in .32 Win Spl and the twist rate was 1:16.  The story is Winchester used the slower twist to reduce fouling when creating a new cartridge for those wanting to reload their own ammunition using black powder and cast bullets.  The standard load was a 170 grain bullet instead of a 150gr yet Winchester advertised the chambering as being a larger caliber, yet with lower recoil than a .30WCF.  Thus it has the designation "Special" in the name.  The .30WCF had a bit of a reputation whether deserved or not for fouling with BP.

I don't know what the twist on the modern Uberti Burgess reproduction actually is, but if it is like my Uberti '73 it is 1:36.  "Modern" .44 calibers rifles tend to run closer to 1:20, that is the big difference.  I know the last .44 mag carbines that Ruger  made were 1:20 twist and they have a bolt gun right now with a 1:20 twist.  I believe I have read that Winchester made the .44WCF in everything from a 1:36 to a 1:40 twist.  If your Burgess is a 1:36 twist that's really not a "modern" twist rate.  The Marlin carbines are all 1:38 .  If you're talking about 2" difference did Quaker Kid know that was all it was?

~Mako

[wildman1]

Cemetary this is a little sideways from what yer askin, however if you go to www.handloads.com you can find several different calculators including one which will tell you the best velocity for your bullet weight, shape and twist rate. WM

[Cemetery]

If your Burgess is a 1:36 twist that's really not a "modern" twist rate.  The Marlin carbines are all 1:38 .  If you're talking about 2" difference did Quaker Kid know that was all it was?

I didn't ask him more about it at the time, just been wondering about it recently.

Never really thought about twist rates till I started shooting AR's, since the people I shot with kept yammering on and on about it.

Lot's of information on this thread, I'll have to come back and kept rereading it.

[Cemetery]

Perhaps we will eventually see a CAD diagram? Or a 30 shot firing test?

+1 on the diagrams.....

[Grapeshot]

Not to upset the applecart, but there were BP firearms that had gain twist rifling.  The Twist rate started out slow and sped up by the time the slug reached the end of the barrel.

The 25mm Chain gun has gain twist rifling to stabilize the ammo fired from the Bradley IFV.

[StrawHat]

Most rifling twists are a compromise as each bullet length (weight) will have a different ideal twist.  Since Winchester or could not be sure what weight bullet would be used, a twist suffiecient to stabilize the range of bullets lengths common to the cartridge was chosen.  Only the express cartridges got a slower twist by design, the 45-90, and 40-82 come to mind. 

Whitworth was sponsored by the British Military to come up with a rifle that would be effective at longer ranges than the standard Enfield of the day.  He eventually settled on the small bore 45 caliber and a twist of 1 turn in 22 inches.  To get there, he had barrels made in twists from 1/70 down to 1/5 (or 1/1, I don't recall).  The 1/22 twist was the optimum for the 500+ grain 45 caliber bullet, and the powder charge he favored.  Springfield put his studies and results to good use when they designed the barrel for the Trapdoor 1873. 

[kurt250]

now days i just don't see why these companys that make these replica firearms don't just make the rifle with the original twist and rifling depth that the originals had. with the cdc machine tools and the cad design computers i would think reproducing one of these rifles or pistols would be a snap. im sure theres some reason that they make these changes, but i can't see why. if anyone out there could tell me i would like to know. kurt250

[StrawHat]

now days i just don't see why these companys that make these replica firearms don't just make the rifle with the original twist and rifling depth that the originals had. with the cdc machine tools and the cad design computers i would think reproducing one of these rifles or pistols would be a snap. im sure theres some reason that they make these changes, but i can't see why. if anyone out there could tell me i would like to know. kurt250

Part of the reason is because today, we are not loading to the factory standard of the late 1800s.  Back then, the 45-90 was considered an "express" cartridge and loaded with a 300 grain bullet and the appropriate twist.  Today, it is considered more of a long range cartridge and uses a much heavier bullet.  Same with the 40-65 and many of the other cartridges popular with the BPCR crowd.  The nice thing is, ig you are building a rifle, most barrel companies offer a variety of twist in a given caliber and you can pick what you think you will need.