.303 Mk 7 ball accuracy requirement

[Steve762]

What was the accuracy requirement for.303 Mk 7 ball ammunition that manufactures had to meet by contract terms or engineering specifications? Was the accuracy standard the same for all nations that manufactured Mk7 ball?

Thx, Steve

Information

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[Surpmil]

Pity Tony E. isn't here to answer that, but this is a sample of what the Textbook of Small Arms 1929 has in 20 pages of detail on the whole process.

One thing is obvious: these standards were not enforced well in WWI as there is no way the rubbish that some soldiers report in their memoirs could have passed the tests described.

It would be interesting to compare the 1909 T.of S.A. and the differences in how the subject is treated. Possibly lessons were learned in WWI, since there seem to have been far fewer problems with poor ammunition in WWII.

Attachment 57416

[Surpmil]

Reading it over again I see the next page is needed.

[Mk VII]

We have had this before but it bears repeating:

Bullet, Barrel And Bulls-Eye

by Captain R.J. Blogg, s.a.c. [NRA Journal, January 1946]


A young visitor to a rifle club for the first time may be amazed to hear, on occasion, the “great ones” complaining bitterly of their rifles and ammunition, and also their armourers. He would imagine there was a conspiracy afoot to prevent the expert from making the high scores of which, in his own mind, he is capable. The visitor, accordingly, will wonder what is wrong with the sport and with the apparatus. These notes are written in an attempt to elucidate the position for the beginner’s benefit.
The objects of the N.R.A are “to encourage rifle shooting throughout the British Dominions and give permanence to the Territorial Army” and to this end have specified that the ammunition and rifles in all major open competitions shall be those of Government pattern. Nothing prevents shooters with a bent towards experimental work and who are in a position to purchase expensive ‘gilt-edged’ apparatus from continuing with their interesting and useful work; special competitions are staged for them, but they may not use their “super” apparatus in the “Service Rifle” competitions. Their activities are not touched on in this article.
The cartridge (Mark 7 ball) and the rifle (in this article confined to rifle No.1, formerly known as SMLE Mark 3) are those in use in the services and it has been laid down by the General Staff that these equipments shall (a) have a certain standard of quality which will render them capable of an adequate performance in action when in the hands of a reasonably well-trained soldier, and (b) be capable of production in factories quickly and in large quantities at a cost which the nation can afford. Here, of course, the necessity of compromise arises.
We all know that if one is prepared to foot the bill nothing precludes one from buying the very best hand-made article superior in performance to anything factory-made. One could buy a Continental-made12-bore shotgun, mass produced and which will kill game, for 50/- or alternatively spend 125 guineas on an English gun built to fit the owner and for which one may have to wait 12 months. In each instance one gets value for money.
Let us now examine the equipments issued:
The cartridge, S.A.A Ball, Mark 7:- made and filled almost entirely by automatic machinery in large factories in lots of 200,000 to 400,000. Subject to rigid inspection by the staff of the Inspector-General of Armaments and issued to the Services after acceptance.
Nothing, however, is perfect; machines, metals and propellants can vary and operators are not infallible. It is necessary therefore, to allow tolerances (i.e. variations) in the specifications laid down for the cartridge by the General Staff; for instance in the proof of a batch of cartridges a tolerance of 3% is allowed in velocity, and the accuracy, when fired form fixed rests, must come within 4½ minutes of angle.
Ammunition can be, and is, made for special purposes in the services, using selected components, hand-weighed charges etc. such should give a velocity variation of not more than 1½% and should group with 2½ minutes of angle. This special ammunition costs 4 or 5 times as much as the mass-produced article and is impractical as a general service issue.
Note:- the Country cannot afford to waste large batches of ammunition which just fails to pass proof. These are usually accepted on concession for “practice only”, for “machine guns only” etc. This restricted sentence ammunition should never, of course, be issued for rifle competitions and club secretaries should be alive to the position and examine the box labels (on which the restricted sentence appears) before accepting and issuing such ammunition.
The rifle No.1 (SMLE Mk.3) – here again the Inspectorate must make allowance, during proof, for wear of tools during manufacture, mechanical and material variations and human error, while still bearing in mind the cost of production. Amongst the many tests a rifle undergoes it is laid down that it should be capable of grouping within 4½ minutes of angle.
From these statements it will be seen that the ammunition and rifle as issued are capable of shooting within, say, 5 minutes of angle; sufficiently close to enable a trained soldier to disable an opponent and, incidentally, for him to qualify on the military target with its 12” bull at 200 yards.
This equipment is not sufficiently accurate for first class target shooting by experts under ideal conditions, and in an attempt at improving the grouping powers of the rifle the NRA, in 1920 permitted the packing of rifles for S.R.(b) competitions, i.e. refitting and adjusting the forend and bedding down the barrel in a resilient material for the purpose of damping down barrel vibrations. While it lasts and when carried out by one of the specialising armourers it will generally serve to improve the grouping powers of the rifle to 2½ minutes of angle or better. The Bisley bull of 5” was adopted so as to be just within the powers of a good packed rifle.
It arises, therefore, that our Rifle No.1, even after packing cannot be expected (chiefly owing to barrel vibrations) to do better than deliver a series of shots much closer than a 5” circle at 200 yards, some at the top of the group and some at the bottom, and it can be seen that should one of the bullets which the bullet puts at the bottom of the group be also from a cartridge producing the high acceptable velocity, it is more than likely that the firer will obtain a 6 o’clock magpie, much to his consternation and annoyance.
Erratic Rifles- many rifle shots, who have the knowledge to make and take pains to keep their barrels in good order, clean and gauged for wear after use, find that on occasion a gun will commence to throw wide groups, although apparently all is in order. This may be caused by one or more faults not generally looked for.
(a) excessive cartridge headspace (also likely to cause blowbacks or burst cases). Remedy: have your armourer fit a new bolt head.
(b) A new barrel from the factory may always shoot badly. During manufacture a barrel may be found which, after boring, is not straight. It will be straightened in a machine, or by a highly skilled operator. It is almost unbelievable, but a barrel so straightened will, as it heats up during firing, tend to reassert itself into the shape in which it was first finished, somewhat analogous to tied-down twig, always trying to regain its natural shape. Proof of this can be obtained by firing grouping tests in special revolving rest. No manufacturer's marks appear on such a barrel indicating it has been straightened. It is just a bad bargain and the only remedy is to scrap and replace it.
(c) Bad shooting of a barrel after considerable use when the bore still appears to be in good condition may be due to leade (leed) wear, which is not easily observable or rarely looked for.
Owing to the extremely high temperature of cordite and its earlier ignition as compared with other propellants, rapid and drastic erosion takes place at the leade. (See Figs. A & B).



This erosion will bring about bad set-up of bullets with the consequent loss of velocity and bad accuracy, thereby affecting the size of the group on the target. The unit armourer tests for wear at the leade with a leade gauge at about point 'A'. He has no means of discovering erosion forward of the leade unless it is so bad as to be visible. If the amount is insufficient for rejection the barrel remains in the service; quite likely it will still group on the military target and is therefore serviceable according to military requirements.
In order to ascertain whether the amount of erosion at points 'B' and 'C' is still insufficient to affect grouping powers, the combined gauging method must be adopted. This is attained by the use of two plugs, a method familiar to most civilian armourers.
There is no cure under present conditions; barrels are made of a carbon manganese steel and are subject to this rapid erosion at the high temperatures developed by burning cordite. Germany did and U.S.A. still do make high class barrels of chromium molybdenum steel to order, for individual customers; they are extremely costly and if obtainable in this Country would doubtless not be permitted by the N.R.A. for open Service Rifle competitions. Such fine barrels when used with the nitro-cellulose powder, which burns at a considerably lower temperature than cordite, will obviate the excessive leade erosion occurring with our equipment.
Shooters who are bothered by loose groups with an otherwise good rifle, using good ammunition are strongly recommended to have their guns "combined gauged", it being presumed, of course, that all possible external faults, bad holding, bad let-off, etc., have first been eliminated.