Most accurate barrel profile

[Col. Batguano]

Just thinking about this a little, barrel profile shapes come in various flavors; straight, swamped, stepped, octagon, round, tapered, and all sorts of other shapes and combinations. They're all a compromise between manufacturing ease (meaning cost) and most efficient shape conducive to acceptable accuracy.

After having watched countless slo-motion videos over the years, it is apparent that ALL barrels flex under recoil. At rest, and under recoil they want to droop at the muzzle. Thinking about the forces involved (mostly up and down but to some extent toward the shoulder of the shooter), it would seem that a somewhat offset egg shape, tapered toward the muzzle would provide the greatest resistance to barrel flexing as the round makes its' way down the bore prior to exit, and thusly, provide for the best intrinsic (barrel) accuracy.

Is anyone aware of some experiments conducted that might have revealed what the "perfect shape and profile" might be?

I realize that total accuracy is not just due to the barrel, but also a function of other things working with it, like projectile shape and stabilization, propellant consistency, total recoil force, and ignition consistency.

The motivation for this question was in looking at some old WW I era photos of very long-barreled artillery, where there were mid-barrel struts and cables attached to them to help ameliorate barrel flexing.

 

[necchi]

Interesting questions, What your refering to is called "Barrel Harmonics".

They're all a compromise between manufacturing ease (meaning cost) and most efficient shape conducive to acceptable accuracy.

But that's kind of a false premise,,
There simply isn't a magic "best". The military command of almost every country globally have been experimenting and developing rifles for 100's of years and have found/made improvements basically only with the technological aspects of metal composition(steels) and manufacture improvments through the centuries.

I realize that total accuracy is not just due to the barrel, but also a function of other things working with it, like projectile shape and stabilization, propellant consistency, total recoil force, and ignition consistency.

That's true, it's refered to as "Harmonic Balance". Finding a balanced load for any barrel is about getting the projectile to leave the muzzle at the same time/each time during the barrels harmonic vibrations. This is much more prevalent in CF hand-loading than our basic ML's. Many barrels/rifles can have 2 or more areas of harmonic balance providing accuracy. Like a low end "plinking" load and another higher charge that some call a "hunting" load.
We all call this "load development", Right(?)

Is anyone aware of some experiments conducted that might have revealed what the "perfect shape and profile" might be?

Sorry to say I don't.
What we have available today as far as barrel profile from the many manufactures of traditional ML's are about physical balance and handling of the rifle and an/or an aesthetic view of the actual historical firearm. They're either made for hard and heavy use of military or durability in civilian market,, or a fine delicate balance for ease of shooting.
Each requiring load development to find the "magic" combination of the load variables that also include each individuals loading technique.

 

[muzzlediscipline]

If you want ultimate accuracy use what the benchrest shooters use massive bull barrels impractical to carry around. This is an area which has numerous approaches. The unmentionable English 20th century military arm had stringent preloading from the muzzle contact to solve the problem. I don't know of any attempt other than heavy barrels which were applied to MLs. Schutzen rifles were about 15 pounds and most of that was barrel.

 

[user 48679]

It was proved over 150 years ago that the best accuracy, if not portability, in muzzleloaders came with very thick/heavy (1-1/4" or thicker) barrels shot from a rest.

(refer to The Muzzle-Loading Cap Lock Rifle by Ned H. Roberts )

 

[Flint62Smoothie]

I would argue that shooting so that the projectile exits at either the upper or lower ‘node’ would be far more advantageous than ‘“just any heavy barrel” where the gun was not shooting aligned or ‘harmonious’ with the inherent harmonics. This has proven out by 1000-yard black powdah shooting, ala Lee Shaver with his Gibbs rifles (an international 1000-yard BP world champion) … so I’d forget about that other article, that is now … so ‘old school’.

Personally, for most of our shooting, that barrel weight per se (maybe less bench or chunk shooting) doesn’t do much, but may improve your hold/follow through, if you are shooting from a ‘node’. And yes, nodes do work for black powder and I have targets to prove it, shooting groups from 50 to 120 grains in 5-grain increments and you could see the pattern/groups be an inch or less or open up to 6” or more! One will typically find 2 nodes in their practical powder distribution/range.

 

[golden sky]

take a round rod, rest it between two fixed points, and add some weight to the center, measure deflection.
take a square bar "same material" rest that over two fixed points and add the same weight to the center and measure deflection..
take an octagon bar .....
take a triangular bar.... yada yada yada.. let us know what your scientific findings are...

i believe its proven that round bar stock has the least strength profile, but square profile is best for resisting stress, but octagon merges square and round for ease of manufactuering in say a 3-4 jaw chuck

 

[necchi]

Grasp this concept.
It's about "learning", it's free.
https://www.varmintal.com/amode.htm

 

[Vaino]

My parents bought me a bench rest rifle when I was 16 ....it had a 1" dia bbl X28" lg and was in .22/250 cal. It weighed 18 lbs w/ the Unertl 18X scope. The action was a pre WW2 Mauser. It only took me 2 hrs to achieve a dime sized group at 100 yds. Later on when my reloads were more consistent, the groups shrunk to 3/8 dia which still wasn't in the "big leagues". My "poor" groups were caused by not weighing the cases ....volumes were important.

So when I sighted in my .45 squirrel LR which had a 7/8" X42" straight Douglas bbl, I was amazed at how easy it was to get 1/2" groups at 50 yds using sand bags. The most accurate achieved load was 30 grs 3f w/ a 0.455 RB and an .018 thick patch. This LR head hit 100s of squirrels. The bbl was button rifled and the grooves were .006 deep and I later wondered why Rice produces bbls w/ .017 deep grooves which are impossible to seal off w/ even fairly tight loading loads. I did the math on this and found that the deep grooves aren't sealed off.

I don't think the average MLer bbl w/ medium to even fairly big loads produces any where near the intensity of the harmonic vibrations that CFs do. .....Fred

 

[nchawkeye]

There is a fellow over near Snow Camp, NC named John Braxton...He is an authority on Colonial Long Rifles and early American History in general...I met him in the early '80s when I got into competitive shooting...He had several guns that he made that won Friendship years ago...I asked this question during a shoot years ago, he seemed to think a .40 caliber with a straight 1 inch barrel made of soft iron shot the best...