Barrel knots and accuracy

My question: No.4 rifle barrel where are barrel knots? How did British engenner to calculate barrel harmonics to estabilish 3-7 pounds upward pressure in order to get tight groups?

Jay Sweet wrote in 1954 that an engeneer calculated in the early '50 knots and anti-knots of No.1 Mk3 bull barrel. Knots are barrel points where barrel itself remains still during the time bullet will exit the muzzle. Knowing those points we coul try a specific barrel bedding while the receiver in still bedded for military handbook.

Yuryev , a russian who wrote about Mosin Nagant and their thin barrels told to cover barrel surface with chalk or other light powder and shoot a few rounds. The place of the barrel where chalk/other powder still remains , those are barrel knots. Those places we could create a contact between barrel and fore end in order to avoid extremely thin barrrel consequenceses. What do you think?

Yep, know all about KNOTS, learnt about them as a boy scout. You could heat the barrel red hot and maybe tie it in a knot.
Now barrel NODES are a different thing, as the No.4 is a bit stiffer than the No.1, it's a bit harder to guess, but with the No.1 it is where the barrel band is located.
I once did an experiment using a moveable weight, 1'' from end of muzzle, 8'' from muzzle, 16" from muzzle, but that was not on an enfield and was a stiffer barrel and 28" long.
Jim sweet wrote something about this in an early (303) edition of Competitive Rifle Shooting, I do not have that article.

Enfield and Woolwich appear to have used an early form of spark photography to monitor barrel recoil movement as far back as WW1, so they were extremely advanced for the era. There were hundreds of different types of trial carried out on the Enfield rifle family, and millions of test rounds fired - they probably had all kinds of test rigs and experiments. Whatever they did, the No4 was a masterpiece of production engineering - a multi-million unit mass produced rifle, capable of match target shooting with the most basic of bedding methods....

Equally capable of frustrating the shooter also if you neglect the basics :):)

The trick isn't stopping the barrel from moving, but making sure it moves the same every time you fire. As the barrel whips, the muzzle goes up and down. If a bullet exits at the top of the whip one shot and the next exits at the bottom, they will not hit the same area. You can leave your barrel as is and adjust your loads until you find one that groups tightest.... once you get into altering the bedding you usually make things worse before any improvement is found. One big issue here is the availability of new foreends to play with, because once mucked up, they are difficult to get right again, especially if using the old techniques. Range shooters decades ago had an almost limitless supply, and quite a few made their own from scratch.

I have on more than one occasion spent many hours getting a rifle bedded only to find it didn't shoot- tried it with a sporter foreend, fully floating barrel and got good results- they can be very pedantic

Soory for my english i called knots what you call nodes. But the meaning is the same. I'm very fascinated with theory that's under enfiel barrel bedding. . For a mass produced rifle of that era it was simply fantastic.no other words are possible to say.

Have you read some of the articles in the Knowledge Library? Have a scan through there...

bow's from Italy in case anybody's wondering.

Barrel movement is a fascinating thing to study.

Movement is not just in the vertical plane. One of the main reasons for vertical "whip" is the fact that the support point of the rifle, i.e. the firer's shoulder on the butt plate, is below the bore line. this is why the FG-42 and numerous post WW2 rifles went for a "straight-line" styling. See Armalite series for starters.

The vibrations start as soon as the striker moves.

When the bullet initially engages the rifling, it is trying to twist the barrel in the opposite direction of the twist. Impact with the rifling also sets up "shock" waves that travel up and down the barrel at high speed.

At the same time, the pressure that is accelerating the bullet through the bore is producing a minute elongation of the barrel behind it.

If the barrel is tapered and has lumps like sight beds attached, all manner of odd things happen to all of these waves as they travel back and forth. That is one of the reasons hard-core "unlimited"bench rest types tend to go with un-tapered barrels with nothing attached to them.

Interestingly enough, however, the chaps at UltraLight Arms are very keen on bonding their barreled actions into the stock, i.e. full-length bedding, but then their stocks are custom made Kevlar-Carbon specials, not a chunk of moisture sensitive wood.

And finally, the "official" bedding regimes, especially on Lee Enfields, were meant to extract optimum consistency from a standard cartridge, usually Mk7 ball. Swap to S&B, Remington , Norma or any of a zillion handloads, and all that is out the window, unless you are very lucky. Even loading Mk7 projectiles in new brass with commercial propellants and primers can be "interesting".

And then there is the question of the correlation (or not) between the sight graduations and the actual trajectory of your bullet of choice.

But that is all part of the fun.

lol, if it was easy , it probably wouldn't be half so interesting.

I have no available MkVII balls and don't know where to looking for them. I reload Sierra and Hornady, sometimes available PRVI PARTIZAN but i find them less consistent . So handloading is a way to control barrel vibrations .. Jay Seets wrote that a gentlemen, Mr. F.G. Price experimentally located nodes and antinodes of a No.1 MkIII with heavy barrel. He found, following Jay Seets book, 8 nodes and 7 antinodes. Last but not least Sweet says that accurate location of those point tell us the location of packing.. It would be very interesting if we found "the experiment" Mr. Price used to locate nodes...

To REALLY understand harmonics you need a degree in music believe it or not. Like vibration, harmonics is really a science in its own right.

On this subject, are there any details around regarding the movement of the muzzle during firing. Presumably the vertical upward movement has been allowed for in the forend aperture design. I have a poorly fitting possibly bent forend on a No4 7.62 conversion which causes the muzzle to deflect left on upward movement but if the muzzle only moves a few thou upward in the forend aperture then does it matter and if so by how many minutes max?.

Bow,

The information about nodes is certainly in James Sweet's book.

The only possible catch is that the data was derived using Mk7 ball ammunition. I do not know if anyone has ever tried to confirm the data using any other ammunition.

Also, "sporting" boat-tailed bullets are not recommended in orginal enfield bores. Such a bullet does not expand in the bore like the old open-based Mk7. Thus there is much greater potential for considerable gas bleed around the bullet. Bear in mind that MINT new Lee Enfield barrels can run out to as much as .320inches effective groove diameter, whilst bore diameter is generally held VERY close to the nominal .303 inch.

If the barrel is already a bit "pre-loved" and suffering from erosion caused by heavy use of cordite-fueled ammo, this gas bleed wil rapidly eat away at the thoat and start attacking the rifling lands.

Quote:

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Originally Posted by Peter Laidler

To REALLY understand harmonics you need a degree in music believe it or not. Like vibration, harmonics is really a science in its own right.

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Mine is not an academic question...I could'n get total knowledge about this phenomenon, not being maths or phisics graduate. So i say: how could i locate the points where the barrel remains more stable during shoot? For me it's enough an empiric way to determine it. Only this.

The next obvious question then Bow is '....why do you want to do this experiment' The reason I ask is that the barrel is what it is and acts how it acts. The reason that it is the MUZZLE that is sound (or free to move but only in one controlled direction - up) is because it is the muzzle that is the very last part of the rifle that has any effect on the projectile before it is alone and free of all outside interference. I know that this is obvious but some people still don't understand this.

I know that someone is going to say next '....... just a minute, then why don't I just bind the muzzle so that it's solidly fixed then?' Good question... You COULD, but the barrel will still whip. And while cartridges are made the way they are and harmonics (it's that word again...) do what they do and vibration acts the way it does, we're stuck with it

Takes me back to teaching physics when sometimes you just have to tell the class that some things happen - or work, like hydraulic principles - because you can't defeat the laws of physics

I agree with you Peter. It's more simple to follow physics laws than fighting against them ( fighting being impossible). I believe packin barrel nodes has a positive effect on barrel stiffening. Hence on grouping capability. But I'm an apprentice and i'm sure wrong. . . But thin No.1mkIII barrel were stiffened this way..
Sorry for my madness words!!