Chapter XII

SPECIFICATIONS FOR BRITISH 18-POUNDER QUICK-FIRING CARTRIDGE CASE AND PRIMER

The following specifications of the British 18-pounder quick-firing cartridge case and primer govern the manufacture and inspection of these cases and primers. They are abstracted from the official specifications and give the most important information required by the manufacturer and inspector.

=Construction.=--The cartridge may be either solid drawn brass or built up, the nature of the alloy and the thickness and distribution of the metal being left to the contractor, except that the dimensions must agree with those in Fig. 1. The maximum weight is to be 3 pounds 1 ounce. If electrolytic copper is used, it must be melted and run into ingots before use. In manufacture the number of drawings and the number of annealings must not be less than six. Should any folds or rings exist in the metal of the base, they must not be removed; any marks of cutting or turning of the metal of the inside of the base will cause the rejection of the cartridge. In the center of the base a hole is to be bored and threaded to receive the primer. The cartridges are to be marked on the base with the numeral and the contractor’s initials or recognized trade-mark.

=Screw Threads.=--The screw threads must, unless otherwise stated, be of the standard Whitworth thread, be cut full, and conform to the government inspector’s standard gages. Contractors may send their gages at any time to the chief inspector to be checked and compared with the standard gages.

=General Conditions.=--The contractor is to supply, with the first delivery, a full-sized tracing, on tracing cloth, of the cartridge he is delivering. The contractor will also supply, free of charge, samples of the metal from which the cases are to be made, if requested by the chief inspector to do so. The samples should not be less than 6 by 2 inches. Cases in stock, that is, cases made before the date of the contract, must not be submitted for acceptance under a given contract.

The cartridges should be delivered in lots of not less than 400. If less than 400 are delivered, the number of rounds to be fired in proof will be the same as if the delivery were the full 400. If, on examination of twenty per cent of a lot, it is found that departures from approved design, or defects of any nature, which involve rejection of the cases, average twenty-five per cent of the number examined, the whole of the lot will rejected.

=Proof.=--(a) Not less than one-half per cent will be fired in proof. At least one cartridge from each 400 delivered will be fired three times, one round being with a proof charge, and the cartridge being (if necessary) reformed after each round. In each remaining cartridge, one proof and one service round will be fired.

(b) The cartridge must load and extract easily, and must not split or develop any flaw or crack on firing.

(c) The cartridge may be sectioned after firing; the section must show no cracks.

(d) The maximum pressure is not to be more than 19 tons per square inch.

(e) If, in the proof of any delivery, defects appear which involve the serviceability of the article, additional proof may be taken from any other delivery not finally closed, to ascertain if the defect is general or not. Should the cases fail at this further proof, the delivery will be rejected without reference to the original proof. The total proof of any delivery shall not exceed five per cent of the number delivered.

=Replacement of Proof.=--The contractor will be required to replace all cartridges expended in proof free of charge, and when the order is approaching completion, he will be informed by the inspector how many are required to complete the number on the order, exclusive of the cartridges so expended, which, whether fired or otherwise tested, will become the property of the government.

=Packing.=--All packages will be so marked that the goods contained therein may be readily identified with the invoice. Unless specified herein that the packing cases or other packing material will become the property of the war department, they will remain the property of the contractor, who is responsible for their removal. Should they not be removed within two months of the acceptance of the cartridge cases, they will be disposed of, and in such circumstances the contractor will not be entitled to make any claim for compensation. The packing cases must be marked “Returnable” or “Non-returnable.”

=Spontaneous Cracking.=--Any cartridge found to be cracked before or after filling, but before firing, is to be replaced by the contractor if such crack is discovered within six months of the date of acceptance of the cartridge in question, which date is stamped on it.

The cartridges may be inspected during manufacture by, and after delivery will be subjected to testing by, and to the final approval of, the chief inspector, Royal Arsenal, Woolwich, England, or an officer deputed by him.

=Primer.=--The primer is to consist of the following parts (see Fig. 2): body _A_; closing disk _B_; anvil _C_; plug _D_; cap _E_; tin foil _F_; ball _G_; paper disk _H_; gun powder _I_; and Pettman cement. The body is to be made of composition metal known as Class “A” or “B.” All other metal parts of the primer, except where otherwise specified, are to be made of brass. The brass is not to contain more than 0.3 per cent of lead, nor to have more than one per cent of total metallic impurities. The Class “A” or “B” metal is to be in accordance with the following requirements: It must be perfectly straight, uniform in diameter, and free from cracks or flaws, and must be capable of standing the following minimum tests:

+---------------------------------+----------------------------------+
| Tenacity, Tons per |Elongation in Per Cent in such a |
| Square Inch | Test Piece as can be furnished, |
| | provided that |
+---------------+-----------------+ |
| Yield | Breaking | Length / √Area = 4 |
| Point | Stress | |
+---------------+-----------------+----------------------------------+
| Class “A”, 20 | Class “A”, 30 | Class “A”, 20 per cent |
| Class “B”, 12 | Class “B”, 20 | Class “B”, 30 per cent |
+---------------+-----------------+----------------------------------+

Pieces of the metals it is proposed to use in the manufacture must be submitted free of charge by the contractor, for testing, when requested by the chief inspector.

=Body.=--The exterior of the body is to be turned and threaded and a flange formed. Two slots are to be cut in the head for the key. The interior is to be bored, cupped, and threaded. The exterior of the body is to be lacquered with a lacquer consisting of:

Seedlac 1 pound.
Turmeric 8 ounces.
Spirit, Methylated 8 pounds.

=Screw, Plugs and Copper Ball.=--A plug having one end turned to form an anvil, which is to be free from burrs, is to be threaded to suit the body. The interior is to be turned out to receive the soft copper ball, and three fire holes bored. A plug is also to be threaded to suit the body, having an annular recess turned on the inner side, and three fire holes bored.

=Cap.=--The cap is to be made of copper and the interior is to be varnished with varnish composed of:

Finest orange shellac 2 pounds 2 ounces.
Spirit, Methylated 8 pounds.

The specific gravity of the varnish is to be 0.885. It is then to be charged with 1.2 grain of the following composition (figures give parts by weight):

Sulphide of antimony 18
Chlorate of potash 12
Ground glass 1
Meal powder 1
Sulphur 1

The composition is to be pressed into the cap with a pressure of 800 pounds. A tin-foil disk, lacquered on one side, is then to be placed on the composition with the lacquered side outwards, and placed under a pressure of 400 pounds. It is then to be varnished with a varnish composed of:

Finest orange shellac 2 pounds 2 ounces.
Seedlac 1 pound.
Turmeric 8 ounces.
Spirit, Methylated 16 pounds.

The specific gravity of this varnish is to be 0.865.

The lacquer for the tin-foil disk before insertion is composed of:

Seedlac 2 pounds.
Turmeric 1 pound.
Spirit, Methylated 16 pounds.

The specific gravity of this lacquer is 0.85.

The cap is to be externally coated with Pettman cement before inserting in the body, and then a fillet of Pettman cement is formed between the body and cap; Pettman cement is made from the following ingredients:

Gum shellac 7 pounds 8 ounces.
Spirit, Methylated 8 pounds.
Tar, Stockholm 5 pounds.
Red, Venetian 20 pounds 12 ounces

=Gun Powder.=--The primer is to be filled with R. F. G.^2 powder, the screw plug being first screwed in and fixed by three small punch blows, and the fire holes covered by a disk of paper secured with Pettman cement.

=Closing Disk.=--A brass disk having a paper disk secured to it on the inner side by Pettman cement is to be placed on the top of the powder, and a ring of Pettman cement painted round the edge of the disk where the metal will be burred over onto it. After the primer is burred over, the whole of the exterior of the disk will also be coated with a thin layer of the cement.

=Marking and Delivery.=--The primers will be marked with the numeral, serial number, contractor’s initials or recognized trade-mark, and date of manufacture. The primers will be delivered in lots of 1000, an additional 20 being supplied for proof with each 1000, or any less number supplied. In the event of further proof being required, the primers will be taken from the lot.

=Proof.=--A percentage of the primers will be selected indiscriminately for proof.

(a) The primer when screwed into a steel block must fire correctly with a 1-pound weight falling 25 inches, and ignite a puff consisting of 4 drams of R. F. G.^2 powder enclosed in one thickness of shalloon, in a 12-inch vent with special receiver, or when proved in any gun for which approved, it must ignite the charge without hang-fire.

(b) A miss-fire, hang-fire, pierced cap, or serious escape of gas through or around the primer will cause rejection.

(c) The falling weight is to have a point of the same shape as the service striker.

(d) Should the firing proof or examination of any delivery bring to notice any defect or defects which, in the opinion of the chief inspector, affect the serviceability of the primers, the delivery in question may be rejected, or further proof taken at his discretion, not only from the particular delivery, but from any others made by the contractor which may be under inspection, to ascertain whether the defect is general. Should any primers fail at these further proofs, the delivery or deliveries will be rejected without reference to any previous proof.

If, on examination of twenty per cent of a lot, it is found that departures from approved design or defects of any nature which involve rejection of the defective primers average 25 per cent of the number examined, the whole of the lot will be rejected. The contractor will be required to replace free of charge all primers expended in proof and examination, which, whether fired or otherwise tested, will become the property of the government.

=Specifications for Cartridge Clip.=--The general dimensions for the cartridge clip are given in Fig. 3. The clip is made from hard-rolled sheet brass in one piece. Four projecting arms are to be formed; the ends of each are bent over as indicated. The clip is sand-blasted, and lacquered with a lacquer composed of:

Vegetable black 1 pound.
Seedlac 1¹⁄₂ pound.
Turpentine (1 quart) 2 pounds.
Methylated spirits (6 quarts) 12 pounds.

One arm is coated with paint consisting of:

Vermillion, dry 2 ounces.
Shellac, dry 1 ounce.
White hard varnish ³⁄₄ ounce.
Spirits, Methylated 1¹⁄₂ ounce.

=Loop.=--The loop is to consist of 13 inches of “webbing, cotton, ¹⁄₂ inch,” threaded through the clip and sewed. Three yards of webbing, selected from the bulk, are to be submitted to the chief inspector before being used. The webbing submitted will be cut into lengths of 11 inches and the ends of each length securely fixed in the clamps of a testing machine, the clamps being 7 inches apart. The strain will be gradually increased until the sample breaks. The breaking strain must not be less than 200 pounds.

=Delivery.=--The clips will be delivered in lots of 1000. If, on examination of 20 per cent of a lot, it is found that departures from approved design, or defects of any nature, which involve rejection of the clips average 25 per cent of the number examined, the whole of the lot will be rejected.