Progressive Depth Rifling: the most misunderstood feature of Civil War-era rifles 

The man really goes the extra mile in his presentation. Really gives the air of a distinguished end of last-century gentleman. The suit, the drink, the audio....

Ref. the expansion of bullets (and this was with a shallow grooved muzzle loading match rifle, not a service rifle with its deeper rifling) . . . In February 1865, W.E. Metford experimented by drilling a hole into a barrel a quarter of an inch above where the base of the bullet would be when the rifle was loaded. A plug was then screwed in, in the end of which was a little point. This hole through the barrel came into one of the grooves; the screw plug was set such that it was not projecting sufficiently to cut the paper of a cylindrical bullet on loading. The rifle was then loaded and fired into damp sawdust. When examined the bullets carried a little line scored in, beginning a quarter of an inch from the base of the bullet. This showed the bullet expanded fully before it had moved any practical amount from its position in the barrel.

Progressive rate rifling is used in artillery to prevent stripping, I was unaware that Progressive depth was used also. I guess it could be called choked rifling.

My immediate guess about how progressive-depth rifling was discovered was that it was an accident. That's usually how huge breakthroughs are made. I even pegged it as a manufacturing error, though I didn't suspect that it was because of trying to rifle a smoothbore.

2 dumb stories - my uncle had an M1861 Springfield he kept behind a cabinet in his house - but he passed and I don't know what happened to it. And just a couple months ago I went to buy an M1841 'Mississippi' rifle in an antique store I'd been going to for 20 years - I used to take it down and fiddle with it for years - only to find the owner had died and the store was now a CPA storefront. Moral of the stories - if you see it, get it.

Thank you for a very non boring video. I find this stuff to be quite fascinating. I bought a Parker Hale 2 band new in 1975, serial #3000. I know that it has progressive depth rifling but never knew what it was all about. 48 years later I finally found out. Thanks for the education!

He oversold his video and he delivered on his promise. That's a paradox, it should not have been possible! ;-)

The question that I have is, HOW did they accomplish the progressive depth rifling?

Did Happen to be watching this at night before I go to sleep, but I made it through.

Thanks Brett! I have an Express cartridge double with Turners Patent Rifling probably made 10-12 years after this. Turner made the first half progressive depth with sloping sides, then the second half constant depth with square sides. Original ammo was paper patched. After a lot of frustration in past years I left it in the safe; now I am having a go at paper patching it.

I love how clinically self-aware you are about how -dull- -boring- exhilarating these videos are. Jokes aside, though - these long, thorough, well-researched videos are my favourite type of content you produce. Thank you for taking the time to put these together!

i think a best way i get it explained is to say the bore diameter is consistent and the groove diameter gets "tighter" towards the muzzle and actually squeezes the bullet smaller at the muzzle.when i say" rifling gets shallower" it confuses people.the land height is consistent if measured from the bore. centerline. great video thanks

I really wish we could convince Italian gun manufacturers to adopt PDR for their Civil War repros, but I guess we're just stuck with buying originals or living with garbage accuracy.

I am so waiting for somebody to come up with a marketable skill from this.

More serendipity in rifling from a century earlier. George Washington was well familiar with long rifles in his wilderness travels as a surveyor, and intended to use them as terror weapons at Boston. Europe had rifles, but none had the range of the Pennsylvania long rifle developed to overcome severe lead shortages in the colonies caused by mercantilism. Pennsylvania gunmakers reduced the caliber and increased the velocities by slowing the rifling twist so a ball smaller than 50 caliber would kill an elk or bison. Probably an unintended consequence, the faster velocity also doubled the range over 60-65 caliber European rifles. At Boston, 300 yard individual shots were documented as well as team firing neutralizing crew targets at 500 yards. General Howe put a bounty on capturing a rifleman with rifle and English rifles like the Ferguson largely didn’t improve in range until that happened.

riveting. there is so much knowledge and understanding to be gained from the past. on a past video you mentioned there are some barrel makers who will do this, if I recall correctly. very interesting subject matter.

Great material for falling asleep. I slept like a log. I'd appreciate more civil war era lullaby. Thank you, Brett, Professor of Musketry.

Well. I still don't understand exactly WHY progressive rifling is a good thing, but that was a bloody good video."It works.". "why, how?", "it just does, ok?"

The French rebored their muskets in order to use heavier bullets, because French bullets were very light compared to the British bullets, so they considered them to be underpowered. The French bullet weighed only 25.6g compared to 31.3g for the English bullet, which gave 1/3 additional penetration at the distance of 270 m. Swedish, Prussian and Russian bullets fall between these two extremes in terms of weight and penetration.

Funnily enough the standard French infantry rifles muskets used uniform depth rifling from 1857. Only the chasseur carbines and artillery musketoons retained progressive depth rifling.

Thanks again for another great video. May I suggest you partner with Cap and Ball on a project? You two do a great evidence based review of firearms and I think you two would be great together.

Well I’m a little disappointed that the knowledge I’ve gained from this wont translate to any marketable job skill in the 21st century but other than that I thought it was a great video. Does anyone sell or make barrels for reproduction guns that have progressive depth rifling or is your best bet to buy an original gun?

Thank you Brett. Well presented. Have ‘fun’ in your deployment……. May it not be ‘interesting’.

This mic is really muffled makes it hard on the folks hard of hearin

Stayed awake for the full 23 minutes Brett.........very interesting and a warning to me when Pedersoli eventually produce their Baker Rifle - shallow rifle grooves.................😩😩

I was actually really excited when I saw the video come up in my feed, especially after the previous one on reproduction rifles!

Fascinating, not boring at all

That was a fascinating explanation, this from someone with no practical shooting experience but a keen interest in history.

I think the real issue with producing a true to form replica is that in many cases the cost would exceed just buying a decent genuine example from the period. Indeed even without the added cost of progressive depth rifling modern replicas are often more expensive than serviceable antiques. Everyone always says they want a modern replica of X rifle until they find out that it will cost 5000 dollars. I know I'm guilty of that.

Watching grass grow.

Well....here's my amateur theory as to why progressive depth rifling is superior with expanding Minie type, soft lead bullets. The bullet has, inherently, a smaller diameter than the bore. This is so it can be easily dropped down the barrel. As such, the bullet relies on pressure to expand its hollow base to contact and then squeeze into the grooves of the rifling. Deep rifling is needed near the breech, because the bullet must squeeze far enough into the rifling grooves to ensure good grip and get the bullet rotating with the rifling but without stripping of the bullet. The high pressure of the charge detonation near the breech is sufficient to expand the bullet sufficiently to fully occupy this deep rifling. As the bullet moves down the barrel, pressure drops. The bullet, which relies on pressure to remain expanded, will inherently contract back towards its resting (atmospheric pressure) size and diameter. Thus, if rifling was the same depth down the whole barrel, the bullet would naturally contract away from the walls of the barrel (both in the lands and grooves) as the bullet moves down the length of the barrel. The pressure seal would be broken, gases would escape past the bullet, chamber pressure would drop, bullet galling would increase and bullet stability would decrease. By progressively decreasing the depth of rifling down the barrel, the grooves of the barrel contract at least as fast as the bullet diameter shrinks due to pressure drop. This would greatly reduce gas escape and ensure the bullet remains tight against the rifling, thereby maintaining bullet stability. If groove depth decreases faster than bullet diameter shrinkage in the grooves (i.e. the bullet actually got squeezed out of the shallowing grooves), then this would force soft lead back into the emerging gap around the bullet in the position of the lands.....thereby maintaining a completely gas tight seal right around the bullet (in both the lands and grooves). Thus, only progressive depth rifling (with a carefully calculated, correct rate of groove shallowing) ensures a perfect, gas tight seal and fit the whole way down the barrel. Makes sense to me.

I survived! Great video as always. Love the historical references and amount of detail. Thanks!

History and guns, my favorites. Combine these with this super geeky gun tech is fabulous.

1st, THANK YOU! This information has kept me from buying a (sadly) poorly made rifle! I can NOT imagine, knowing that the rifling needs to be made MUCH deeper, Pedersoli continues to make what I am going to call defective rifles. It also has convinced me to do research on the depth of the rifling of their cap and ball revolvers. Which I am planning to buy very soon. I am glad that you made this video, and that I watched it!

18:20 I can understand why recreating the progressive depth rifling would be difficult/ expensive to do for the repro makers, but I don’t understand why they wouldn’t at least have constant depth of a more period correct depth. Getting larger dies can’t be that difficult for the makers.

Great content. Did the US stop using progressive depth rifling sometime before ACW? I was thought I read that someplace. I think Enfield kept using it….

Excellent presentation! Very interesting historical information, regarding how progressive depth rifling was made and how the accuracy from progressive depth rifling was discovered!

Brett great conversation as usual! Do you ever talk about “gain twist” rifling? What’s the deal with that? Keep up the great work sir!

I really enjoyed that, cheers Brett!

Dziękuję :D Świetny wykład Panie Profesorze :D Gratuluję prostego i historycznego wytłumaczenia gwintu progresywnego. Dobra robota !

Enjoyed this presentation.

Very interesting! Thanks for sharing!

I follow your posts because they are informative and interesting. I have a particular interest infirearms from the early to the mid 19th century. Your general post have cleared up a number of points for me and your specific dives into such subjects a s gun cotton and other innovations are full of information and add interesting detail to the period. Thank you.

interesting thank you

Great video. I really appreciate your efforts! You're visuals are great!

Excellent video.

Perhaps the marketable job skill would be to learn how to recut those modern made barrels to give them the proper rifling form. I could see that as an interesting project to consume a few years. Meanwhile I'll stick to my PH reproductions.

Thank you for all the great information!

This subject is fascinating. First learned about it on the video about Italian replica rifles. Great content!

Great video!

Very informative, as always. I had forgotten about this, I own and have read Manns book. Do you sell a book on paper cartridges? I see a few books on your your bookshelf that have the same title.

Another great video.

Well done Brett.

An excellent and entertaining video, thank you Professor 😉 seriously good knowledge.

Really enjoyed that video. So I have a P-H early British P53 that I know has PR, but I also have a contract original P53 from 1862. Would the contractors have used PR by then?

I watch Cap & Ball, and C&rsenal, so I found this topic very interesting and informative, just for its historic value ! I'm also an EE, and have been using an programming microcontrollers (uC), almost since their inception. But as a hobby, I design analog circuits (no digital parts, as those uCs) that wouldn't even been economical in the past, but do mostly as an interesting deviation, that maybe a friend, in the hobby, might employ, but has no benefit in anything marketable.

Do you have pictures or blueprints of these tools/machines that can cut progressive depth rifling? It would be interesting to do a video on the machines of that era and how they worked.

My question is... HOW did they cut them progressively?

Just wondering, with the modern constant depth rifling barrels would a copper bullet made to the minie or Pritchett form perform better or is it about the same regardless of whats used?

Interesting stuff

your outfit is impeccable ! your seperate collar shirt is my favourite !!!!!!!!!!!

A few pictures, diagrams or photos would be perfection.

DAMM good history video👍👍

Very interesting listen! I never bore of these videos. Hearing you discuss it a few times now I am determined to get my Italian 1861 rebarreled to have the correct rifling. I looked up the two barrel makers you mentioned in the other video, Whitacre and Bobby Hoty. Do you recommend one or the other or either one a great choice to go to?!

Ok, I understand How progressive grooves work, if not why, but, How is it accomplished? If you were to measure at the lands with a bore micrometer, at the breach, and at the muzzle are they going to read the same internal diameter? If you took a barrel and turned it down on a lathe so that the muzzle Outside Diameter is the same as the breach OD, and measured from the groove to the OD, are they going to be the same at breach and muzzle?

The progressive nature and decreased diameter is the principle behind squeeze bore designs to boost velocity. In WW2 the German army had a squeeze bore anti tank gun with tungsten penitrators. It's still exceptionally accurate 😉

Progressive rifling sounds like it's was a purposely done...the surprise was the accuracy was improved. Gotta luv the French.. Their engineering is quirky but in many ways better...BTW luv French cars, Motocycles, & military hardware.

Kind if off topic but is it possible to use a burton bullet in a Pritchett style cartridge? I like idea of just breaking off the bullet from the powder cylinder instead of clumsily taking it out of the wrapper. The reason i ask is because Pritchett bullets are rare and hard to come by, even the molds, while burton bullets are everywhere. Perhaps this is an idea for an experiment video?

Thank you for the education, it is nice to know more about the rifle that I hold in my hands, especially the unseen stuff that is inside. In my case it is a Colt 1861 Special Contract Musket which is marked 1864. I find the the technical information very interesting, can you tell me the source documents that you show as I would love to find out more. Don't get me wrong, listening to you is great (which is why I'm here) but I also like to read and re-read the original technical books if possible... ... and thanks again for taking the time to put this together. 👍

Ah, professor, but how did they do it? I can't see them rifling in quarter lengths and then pulling a spring loaded cutter through to smooth the gradient as an industrial ptocess.

So, anyone know where I track down a decent attic-find Pattern 1853 with progressive-depth rifling?

This is a great video, but I am very dubious that progressive depth rifling is any more accurate than constant depth rifling of adequate depth. I have seen many photos on the Shiloh Sharps board of snow bank recovered bullets that show even 1:16 alloy fills the tinest of voids. You can even see a line where a paper patch ends don't quite meet. I have talked to several N-SSA top shooters who will say that a constant depth rifling is just as accurate. I am not saying you are wrong it just dosen't make good sense to me why the need for progressive depth rifling rather than deep enough rifling to grab the bullet. I can see how a fouled barrel could shoot better with progressive depth rifling, but that is a different story. It would be super interesting to get a high speed camera to see if the thin rifling are failing to stablize the minie as compared to a Whitacre barrel. I suspect you are correct, but I think a .15" constant depth would stablize the minie just fine.

I wonder if anyone can do this to a rifle that already has a constant rifling. Sure would like to have it done to my black powder gun

Didn't the French develop a rifle that was smooth bore except for the last 4" from the muzzle was rifled. Examined by other countries revealed it to be as accurate as any rifle of the period.

Oh bugger, I have gained new knowledge of little practical use in the modern age but alas have forgotten how to tie my laces😢humbug

What companies offer barrel relining services for existing Italian rifles? Who produces new barrels with progressive depth rifling that fit on Italian guns?

Might there be an advantage in the progressive rifling reducing the profile of the flying bullet - in pushing down the spiral fins that form on the bullet when it bullet first expands?

🥇🏆

As to how progressive rifling works we need to look to the Bernoulli effect as to how that works 😊

The audio sounds off at the start of the video.

How do you make this rifling?

When was the progressive rifling abandoned? I'm assuming some early cartridge rifles were progressive because of all the muzzle loaders that got converted. Was it is copper jackets or smokeless powered that pushed the change back to constant depth?

Wouldn't this also allow for less fouling? Gives more place for the carbon to build up?

Isn't this in effect a kind of mild tapor bore? It reduces the area of the bore, no? I would expect that this might well increase the accuracy of any rifle, not just an expanding bullet muzzleloader. It would be really interesting to try a 5R gain twist, progressive depth breech-loading rifle. Could call it "Kitchen Sink" rifling because you're throwing every rifling tweak you can think of at it.

Would a compression bullet work better in repo rifled muskets?

Do you know the groove depth on an Armsport Richmond carbine?

UBER KOOL SO DID EARLY GUNSMITHS .. KENTUCKY LONG RIFLE, DO IT IN SMALL SHOPS , TOOLS INVOLVED AND THEY MAKE THE TOOLS MUST HAVE BEEN STILL GOING ON 1800S RIGHT 😅

Does the sharp's rifle have progressive rifling?

What you didn’t answer is why modern Italian replicas don’t use progressive rifling? And why such shallow grooves? Why not match what they did in the 19th century?

i was laughing my ass off.

Hey pal! It is me again, I have commented over your recent video about the "worst" rifle in the civil war, I wanted to say i have a problem, I have adhd, Not only that, Autism, that means My topics tend to be narrow, can yoy advice me how to hyperfocus on things i may like at least, but not narrow on? ❤😢 I do not actually have a narrow topic, at least not yet, im 16, plus my autism is very mild and high function, maybe thats why. So please, can yoy give me advice for finding something gokd to waste time on and hyperfocus?😊 ❤❤

So I have a modern made (relatively speaking) Birmingham made Parker hale rifle 1853. I’ve been told one of their redeeming features is that they have historically accurate progressive rifling. Do you know if that is true

I wounder? Why? has this Gone Away? so far away? searching for Ever better accuracy and performance how could this tech work today? with To Days Tech? I totally could see the logic and Possibilities or Benifits with pure lead! depending on engineering or skills? I suspect this worked with the PSI curve as the PSI droped in a different curve with or Without the Progress?

Can't hear you

Why is progressive rifling not used today? I understand that bullet expansion is no longer a thing, but the bullet is still forced into the rifling. It seems if progressive rifling was good then, it could still be good.

I've always wondered what would've happened with expanding bullets and the squeeze bore principle.

Thanks for telling the truth about Pedesoli repos. They are over priced shit. Traditions is another one I would never buy too. All more modern BP rifles are tight bore and require expensive proprietary bullets. It's all marketing bs.