Progressive Rifling

[StonewallSharpeson]

Hello, can anyone tell give me some specifics on the progressive used in Civil War era muskets? Firstly, was the progressive rifling used have both progressive depth (deep to shallow) and progressive rate of twist (slow to fast), or just one or the other? Did the specs vary based on manufacturer or model?

Does anyone know the progressive depths and rates of twist (progressive or not) for these common civil war era firearms: M1855, M1861, rifled .69" muskets (eg M1842, percussion conversions, and flintlocks), P53 (which models?), Lorenz

Was the rifling different in the rifles of the muskets (aka "two banders") or other carbines, including breech loaders, which used solid conicals rather than minies?

Thanks for your help!

[Craig L Barry]

Re: Progressive Rifling

Enfields after 1858 feature this kind of rifling. The groove diameter at the breech was .015" deep, going to .005" at the muzzle. The ball would expand into the deep groove when the charge went off. As such the ball gets a good "bite" on the rifling as it moved toward the muzzle. As it moves, the ball gets squeezed down in the groove area and stops any "gas cutting" that might effect accuracy. The bore diameter is the same all the way through the barrel, only the rifling is cut deeper. The rate of twist was also not changed.

This enhancement was actually (they say) discovered by the French when attempts were made to rifle their supply of old smoothbore muskets. They used shallower rifling toward the muzzle because of the thinness of the barrel. The story goes they found it positively impacted the accuracy.

[Curt Schmidt]

Re: Progressive Rifling

Hallo!

In brief...

"Firstly, was the progressive rifling used have both progressive depth (deep to shallow) and progressive rate of twist (slow to fast), or just one or the other? Did the specs vary based on manufacturer or model?

Does anyone know the progressive depths and rates of twist (progressive or not) for these common civil war era firearms: M1855, M1861, rifled .69" muskets (eg M1842, percussion conversions, and flintlocks), P53 (which models?), Lorenz"

The answer is yes, but it varies,, and is not consistent..

For example most of the British "line" of the ACW era was progressive depth rifled except for the Pattern 1862 Whitworth Rifle which was standard.Enfield RM twist was 1:78, 1:48 for the P1858 Naval Rifle, but 1:79 for the P1856 and P1860 Short Rifle. Groove depth for the P1853 RM was .005 at the muzzle and .013 at the breech.

On the US M1855/61/63/64 RM side, "thanks" to the Italian repros... the barrels are often considered 'standard' depth but are not. Twist (pitch) was 1:72, uniform twist. Groove depth at the the muzzle was .005 inches and at the breech was .015.

Where one generally sees the most varying twist is in carbines and revolvers which rather than shooting expanding base projectiles shoot oversized balls that get squeezed down into the rifling.

Curt

[Gary of CA]

Re: Progressive Rifling

I was talking to the machine shop instructor at TSJC gunsmithing school and raised the subject of progressive rifling.

He concurred that you cut the groove along the length of the barrel to the minimum depth first. Then as you want it to go deeper, you add a shim to get that extra .0001" (or whatever) for the shorter length. The process is repeated for each groove and when they're all uniform, you add another shim. It's a rinse and repeat process until the progressive depth is attained.

If anyone else has any ideas as to how the progressive depth was cut, I'm all ears. Thank you.

[James Brenner]

Re: Progressive Rifling

Hmmm. That may be applicable to civilian gunsmiths where the time needed to rifle a barrel was not terribly important, but for government operations, I very much doubt that using shims was even an option. In fact, I know it wasn't. Here's why: in 1856, Cyrus Buckland of Springfield Armory created a rifling machine that used an "expanding cutter ... capable of cutting grooves of ever decreasing depth. The machine could rifle a barrel in 25 minutes." (Felicia Dreyrup, Arms Making in the Connecticut Valley. This was a huge change from just 8 years before when it took an hour to rifle a single barrel. There are several other accounts in both Harpers New Monthly Magazine as well as Scientific American reporting on improvements in rifling machines during the immediate pre-Civil War period as well as during the 1861-1865 period. All of the improvements were intended to speed up the process of rifling a barrel. Some of the improvements allowed for rifling more than one barrel at a time while other designs permitted all three groves to be cut simultaneously. The St. Louis Arsenal had the capability to rifle three barrels all at once while both the Allegheny and Benecia Arsenals could rifle two at a time (Annual Report of the Secretary of War, 1857). Between 1862 and 1864, for example, three patents were granted to inventors for new rifling machines: George Bigelow in March 1863; Christian Sharps in December 1862; and Tiros Powers also in December 1862: all made the rifling process more efficient and less time consuming. Miles Greenwood of Cincinnati was able to rifle about 27,000 muskets between 3 July 1861 and 15 December 1861. He could not have afforded to use shims - either because of the labor costs involved or to meet the time requirements of his contract.

This was in the beginning of the industrial age when mass production was taking baby steps and most of those steps were taken in the ordnance field. Check out the video on the American Precision Museum website to see an animated demonstration of rifling operations at the Robbins and Lawrence Arsenal in 1853 to see how automated the process had become.

I hope this helps a bit.

Jim

[Gary of CA]

Re: Progressive Rifling

Yes it does. Thank you Jim.

To have an expandable reamer, it must have been mounted on a threaded rod that when rotated, forced the cutters higher or lower (depending on the rotation).

[James Brenner]

Re: Progressive Rifling

You're welcome, Gary.

It would be nice to know exactly how they did it. The slider and sine bar shown on the APM animation hints at the procedure, but not in any great detail. By the way, in case you're interested, the patent drawings for Powers', Sharps' and Bigelow's rifling machines are available on Google Scholar. If you type in "rifling machines", you'll find not only descriptive information, but images of the patent drawings as well. Bigelow's patent number was 38,000. Sharps was 37,057, and Bigelow's was 37,054. I'm not a machinist by any stretch of the imagination, so I have trouble deciphering some of the patent drawings.

It's unfortunate that none of the musket rifling machines seem to have survived over here. Robbins and Lawrence provided machinery to several different arms makers including the Enfield Manufactory in 1856. It's possible that one of the machines is in a museum somewhere in England. It's also too bad that the Robbins and Lawrence letter books got scarfed up by a collector (John Hintlian) years ago and have since disappeared. It would be interesting to know the extent of the cross-pollenization that went on within the arms industry.

Jim

Jim

[Don Dixon]

Re: Progressive Rifling

The Austro-Hungarian Army (k.k. Army) used a variation of progressive rifling in the Muster 1854 System Lorenz family of weapons. The lands and grooves were opened up by approximately one Punkt [0.00717 inches/0.182 mm] from the breech to five or six inches [127 to 152 mm] down the bore toward the muzzle. This left the grooves approximately 0.025 inches [0.635] mm deep at the breech and 0.02 inches [0.508 mm] at the muzzle. This was called the Ründung [drop or fall]. Relieving the lands and grooves at the breech created a progressive rifling system at the breech. When the rifle was fired, the bullet slugged up in the Ründung and was then squeezed down in the remainder of the bore. That ensured that the bullet was a tight fit in the bore. But, the rifles -- particuarly the breech -- required very careful cleaning, which the 1857 System Lorenz manual is positively anal about [The soldier will do. The non-commissioned officer will inspect. The officer will inspect. Etc.] The Austrian manual notes that the beginning of the Ründung can be noted when loading the rifle because the bullet settles much more easily on the powder from that point in the bore of the rifle. The Ründung can also be noted when cleaning .54 caliber Muster 1854 arms, in that the patch on a cleaning rod feels looser at the breech than in the rest of the barrel. Standard American 2.5 inch square military cleaning patches will generally come off of the end of an American barracks style cleaning rod when the rod is withdrawn from the Ründung, and then have to be fished out with a worm. The wrap jag cleaning device used by the k.k. Army avoided this problem. A Federal or Confederate soldier who was not equipped with k.k. Army cleaning tools would have experienced difficulty in keeping the breech of his rifle clean, which undoubtedly contributed to complaints that Muster 1854 weapons quickly fouled at the breech, making them difficult to load. (Austrian Army Manual (Infanerie-Feuergewehre), passim)

Regards,
Don Dixon

[Gary of CA]

Re: Progressive Rifling

Thank you Don Dixon.

[buckandball]

Re: Progressive Rifling

I have a reprint of the late 1850's US Ordnance manual that goes into great detail on this subject, the adoption of the minie ball, comparisons of .58 and .69 performance, and then has additional appendices on the P53, etc. I happened to thumb through it just the other day. When I get home from work I'll post the title, as it is well worth owning a copy. It discusses the trials that went into the type and style of rifling adopted, among other things, to include the testing of, but not adopting progressive twist rifling... I do not recall it actually going into detail of the specific machining processes of how they did progressive rifling.

Edit/Update: The book is titled "Small Arms 1856"

https://www.amazon.com/Small-Arms-1856-Experiments-Military/dp/0939631016