Ball burnishing?

[RJW NZ]

I've just taken on a newcomer to my gunsafe, its a no1mk3 target rifle. The barrel is a no1mk3 profile and stamped on the flat 'regulated by fulton', the receiver is stamped AGP AG Parker Ltd.
The muzzle has been milled off, perhaps crowned would be the right word, I'm not sure, in any case the front face of the barrel has been taken back about 1/8th of an inch.

The question is, if this has been ball burnished, and the usual ID on the barrel front is gone, is there any internal visual clues to know if it has been done?

Information

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[Son]

IIRC, ball burnishing is a process where a lead slug was cast onto a rod in the bore and then drawn back and forth with a lapping paste on it. The process was supposed to remove all the microscopic (and not so microscopic) tears in the surface of the rifling from the broaching process that formed the lands and grooves. The idea was to remove the need to "run in" a barrel, but there was evidence it shortened the accurate lifespan of the barrel also.
Early in production some No5 MkI barrels were ball burnished, I think the mark was a P inside a circle on the knox...

I don't think there would be any way of knowing if Fulton's marks were at the muzzle and had been removed.

As usual, I'll take any degree of corrections on the above- "no books were disturbed in the preparation of the answer"....

[jmoore]

Dang, I need that disclaimer! ("'no books were disturbed in the preparation of the answer'....")

RJW, is the muzzle face altogther flat, or is there some degree of chamfer or edge break at the rifling terminus? (Not directly pertinent to answering your question, its just curiousity.)

[Peter Laidler]

I was told that the act of ball burnishing (come on lads......, keep it clean and no jokes please......) was by drawing an exact diameter ball-bearing down the bore. In doing so, it ensures that thediameter of the bore across the lands is exact, all the way through and that while being drawn through it spread the steel of the lands so that the corners of the rifling were dead square and sharp.

This is on the basis that it's the bore that gives the bullet accuracy and the rifling that give it stability. It's not quite that simple and there's more to it than that of course............... Anyway, ball burnishing, makes the bore perfectly parallel and leaves a mirror finish. For how many rounds is a matter of conjecture.....................

[RJW NZ]

The end of the barrel is machined dead flat, almost flush with the nosecap surround, with a tiny chamfer into the bore.

It used to belong to the RNZN, probably the navy shooting team, so (although ithere's questions as to why there's Fultons plus AGP marks on it when they're separate businesses) I can imagine that the navy armorers may have crowned the barrel to remove suspected problems there. Its a multi groove bore and dead shiny, but my suspicion is that without a microscope there's no way to know if burnishing had been done.
If the RNZN doesn't have those kind of armorers then perhaps Fulton's did it.
Lovely rifle, really looked after. I'm a bit swamped at the moment but I think I'll ask Badger if I can post another photo profile in a few weeks. Quite different accurizing methods on this rifle compared to the Fultons profile we have already.

[Mk VII]

I've got a Fultons one and the crown is flat on that as well.

[Son]

Spotted Peter's response earlier and went looking for info on ball burnishing. Only found references to surfaces in general, but applied to a rifle barrel it would be exactly as he has described.
I'll see if I can find where I got my info from, I may have a crossed wire- the method may be for another type of finishing process.

Was there a defined list of work that went into a "Regulated by Fultons" rifle? Or was it the choice of the customer what was done to his rifle?



Note, just found the process I refered to earlier is "draw lapping", not ball burnishing.... apologies

[Mk VII]

“ This is a barrel finishing process which we acquired in the year 1922, through the good offices of the late Mr. T. B. Simpson, a Bisley visitor from Australia, where he represented a well-known British firm of pump manufacturers. Mr. Simpson brought over sectioned barrels, one of which had been burnished by passing through sized steel balls under pressure. The difference between the unprocessed barrel and the other was remarkable, especially at a time when riflemen were troubled by the presence of hard metallic fouling which in some instances seriously affected the accuracy of their barrels
“ The sectioned barrels showed that the ball burnished barrel had a dark mirror-like perfectly smooth surface on the lands, whereas the other barrel, although well rifled, had innumerable cross-cuts on the lands which under the great pressure which the bullets exerts on the bore, scrapes off some of the metal jacket of the bullets until an excessively hard lump of metal forms which cuts into the passing bullets and destroys accuracy.
“ Ball Burnishing closes up these cuts on the lands and although it does not touch the grooves it is rarely that any metallic fouling collects there as these grooves are cut longitudinally, i.e. in the same direction as the passage of the bullet, therefore, there are no cross cuts to scrape the bullet skin and, therefore, no hard fouling of any consequence.
“ In a barrel that is worn, the edges of the lands become rounded, thus reducing the area of contact available to the ball in the burnishing process; it follows, therefore, that Ball Burnishing is most effective when applied to unworn barrels. For this reason it is to be recommended chiefly for application to new barrels, thereby improving their initial levelness and the homogeneity of the wearing surface of the lands giving an expectation of greater accuracy, longer life and less likelihood of collecting metallic fouling………
“ Ball Burnishing enlarges the average bore by approximately one half thousandth part of an inch, an almost infinitesimal amount which in no circumstances can cause any detrimental effect.
Many marksmen using Service rifles are misled into error in specifying precise bore sizes when placing orders for new barrels or new rifles. It is impracticable within the tolerances maintained under present day conditions [1961] to furnish barrels with bore sizes which were current before the second World War.
“ New barrels today are officially acceptable when made between .301 and .304 gauge, but 98% of new barrel production is found to gauge between .301 and .3025……….”

[Peter Laidler]

From an enineering point of view I can't see how a ball can be forced up or down a barrel by hydraulic pressure or by a rod because on the cformer the fluid would leech past the ball and dynamically (?) you wouldn't do it by pressing the ball using a rod. It'd have to be drawn or pulled through, as in button rifling. There's a thought.............. Thinking out aloud....., I wonder if that's where the idea of drawn button rifling comes from..............

[JBS]

I think,,,, by your description that your muzzle has been crowned and lapped. Muzzle lapping is the process where a brass sphere on a rod is covered with a fine grinding compound and then set in the exoduses of the bore and spun by hand. It makes the termination of the rifling concentric. The tell tail sign of this is what looks like a slight cone right where the bore stops. If this was done the cheep way with a cutter it will look deeper and the cone will have rings in it left by the cutter.