The History of the Royal Society of London/Part 2/Paper 10

by William Brouncker

EXPERIMENTS

Of the Recoiling of

GUNS.

By the Lord BROUNCKER.

Fig. 1WHen I was commanded by this Society, to make some Experiments of the Recoiling of Guns: In order to the discovery of the cause thereof, I caused this Engine that lies here before you to be prepared, and with it (assisted by some of the most eminent of this Society) I had divers shots made in the Court of this College, near the length thereof from the mark, with a full charge (about a four-penny weight) of Powder; but without any other success, than that there was nothing regular in that way, which was by laying it upon a heavy Table, unto which it was sometimes fastned with Screws at all the four places R, L, V, B, sometimes only at R or L, having wheels affixed at L and V, or R and B, that it might the more easily recoil.

This uncertainty I did then conceive might arise from one or more of these three causes, viz.

1. The violent trembling motion of the Gun, whence the Bullet might casually receive some literal impulse from the nose of the Piece at the parting from it.

2. The yielding of the Table, which was sensible.

3. The difficulty of aiming well by the Sight and Button so far from the Mark.

Therefore to avoid all these, the Experiments I caus'd to be made before you in the Gallery of this Colledge, you may be pleased to remember were performed, first, taking only eight grains of Powder for the charge. Secondly, laying the Engine upon the Floor; and, Thirdly, aiming by a Thread at M, a Mark about an Inch and 3/4 from the Mouth of the Gun (the edge of a knife being put for the Mark, the better to discern the line that was shot in) and they thus succeeded.

When the Piece was fastned to the Floor both at R and L, the Bullet then did so fully hit the Mark, that it was divided by it into two parts, whose difference in weight was less than ten grains (about the thirty third part of the whole Bullet) although the lesser part was a little hollow, and that from which the neck of Lead was a little too close pared off: But when hindred from Recoiling only at R, the Bullet mist the mark towards L or A, for the whole Bullet, less than two grains excepted, went on that side: And in like manner when hindred from Recoiling at L, the Bullet mist the Mark towards R or B, the whole Bullet, less than two grains excepted, passing the knife on that side thereof.

I had the honour to make other Experiments with the same Engine, lately at White-Hall, before his Majesty and his Highness Royal within the Tilt-yard Gallery, where there is the hearth of a chimney raised a little above the Floor, about the distance of thirteen feet from the opposite wall, against which I caused a plank to be placed, and the Engine to be laid first against the middle of the Hearth, that it might not recoil at all, and that part of the board to be marked against which 'twas levelled, known by a line stretched from the Breech of the Piece unto the Board, directly over the sight and button; and the fire being given (the charge being but eight grains of Powder as before) the Bullet did fully hit the mark. Secondly, the Piece (charged and levelled in the same manner) was laid at the end of the Hearth next the Park, so that very little of the corner R, rested against it, and then the Bullet miss'd the mark about an inch and a quarter towards the Park, or A. The like being done at the other end of the Hearth, the Bullet then miss'd the mark as much the other way; and afterwards with double that charge something more, as before I had found it less with a smaller charge.

Since this (at first designing only to experiment the several distances that the Bullet is carried wide of the mark with different charges of Powder) I made these Experiments following.

In the first Column whereof you have the corner stopt from recoiling.

In the second the grains of Powder with which the Piece was charged.

In the third the distance the Bullet was shot wide from the mark in inches, tenths, and parts of tenths.

In the fourth the side on which the Bullet was carried.

In the last the distance of the mark from the muzzle of the Gun in feet.

B	16	0.	N	9	L	40	0.11/4	L	9	L	12	1.11/4	R	6
L	16	1.71/2	R	9	L	38	0.11/2	R	9	L	48	0.01/4	R	1/4
R	16	1.5	L	9	L	39	0.01/2	L	9	L	48	0.11/2	L	2
R	12	1.5	L	9	R	39	0.1	L	9	L	48	0.21/2	L	4
L	12	1.71/2	R	9	R	12	0.6	L	2	L	48	0.51/2	L	6
L	8	1.6	R	9	R	12	0.91/4	L	4	L	4	0.11/2	R	1/4
R	8	1.1	L	9	R	12	1.2	L	6	L	4	0.11/2	R	1/4
R	4	1.0	L	9	R	12	1.51/2	L	8	L	8	0.31/4	R	1/4
L	4	1.11/4	R	9	R	12	1.9	L	9	L	12	0.3	R	1/4
L	24	1.11/2	R	9	B	12	0.1	L	9	L	16	0.21/4	R	1/4
L	32	0.6	R	9	R	12	0.3	L	1/4	R	48	0.0	N	9
L	40	0.11/2	R	9	L	12	0.31/2	R	1/4	R	48	0.1	L	9
L	48	0.41/2	L	9	L	96	0.01/2	R	1/4	L	48	0.01/4	R	9
R	20	1.01/2	L	9	R	96	0.01/2	L	1/4	L	4	1.6	R	9
R	20	1.4	L	9	R	96	1.2	R	2	L	4	1.51/2	R	9
R	641/4	0.73/4	R	9	L	96	0.2	L		R	4	1.6	L	9
L	641/4	0.9	L	9	L	48	0.11/2	R	1/4	R	8	1.8	L	9
L	96	1.1	L	9	L	48	0.0	N	2	L	8	1.8	R	9
R	96	0.73/4	R	9	R	48	0.11/4	L	1/4	L	12	2.0	R	9
R	96	0.8	R	9	R	39	0.31/2	L	9	R	12	2.1	L	9
R	96	1.3	L	9	R	39	0.2	L	9	R	16	1.71/2	L	9
L	96	1.31/2	L	9	R	40	1.2	L	9	L	16	1.8	R	9
R	12	0.31/2	L	6	R	40	0.0	N	9	L	20	1.5	R	9
R	12	1.3	L	9	R	40	0.2	L	9	L	20	0.2	R	1/4
L	12	0.63/4	R	2	R	96	0.61/2	R	9	L	24	0.21/4	R	1/4
L	12	1.03/4	R	4	L	96	1.01/2	L	9	L	28	0.1	R	1/4
L	12	1.21/2	R	6	L	96	1.01/2	L	9	L	32	0.11/2	R	1/4
L	12	1.41/2	R	8	R	96	0.71/2	R	9	L	36	0.11/4	R	1/4
L	48	0.5	L	9	R	96	1.0	R	9	L	40	0.1	R	1/4
L	56	0.8	L	9	R	40	0.8	L	9	L	44	0.01/2	R	1/4
L	96	1.21/2	L	9	L	40	0.5	R	9	L	48	0.01/2	R	1/4
L	96	1.5	L	9	L	48	0.1	R	9	L	52	0.01/4	R	1/4
L	40	0.5	L	9	R	48	0.01/4	L	2	L	56	0.01/4	R	1/4
R	46	0.9	R	9	L	12	1.7	R	9	L	60	0.01/8	R	1/4
B	8	0.2	R	9	L	12	0.21/4	R	1/4	L	64	0.01/8	R	1/4
R	96	0.6	R	9	L	12	0.61/2	R	2	L	96	0.0	L	1/4
L	96	0.9	L	9	L	12	1.0	R	4

Whence you may be pleased to observe:

First, that the recoil of the Piece being hindred only at R or L, whatsoever be the charge of the Powder, the Bullet still misses the Mark, placed at the Mouth of the Gun, on the same side that the recoil is made.

Secondly, That about twelve grains of Powder shoots widest from the Mark at all distances above-mentioned, on the same side that the recoil is made.

Thirdly, That above Forty-eight Grains of Powder shoots wide from the mark, placed at nine foot from the Muzzle of the Piece, on the contrary side to that on which the recoil is made.

The Cause of the first I cannot doubt to be the recoil of the Piece (from the Force of the Powder) before the Bullet be parted from it.

The second is, as I conceive, because with less than twelve Grains the Piece ceaseth to recoil before the Bullet be parted from it. And with more than twelve Grains the Bullet is parted from the Piece before it hath recoiled so far: A greater power not moving a greater weight swifter (horizontally) in the same proportion that it doth the lesser.

And for the third I have this to offer, viz. Because the Mouth of the Gun is moving sidewards whilst the Bullet is going out; therefore the Mouth of the Piece must be contiguous (at least) unto the Bullet on the contrary side to that on which the Piece recoils, some time after the separation made on the other side, and therefore the last impulse of the Bullet from the force of the Powder is on that side the Piece recoils; wherefore the Bullet must necessarily cross the Axis of the Piece, and that with a greater or lesser Angle, according to the force of the Powder, and when this Angle therefore is greater than the Angle of recoil, then must the Axis of that Cylinder in which the Bullet moves cross the Axis of the Mark, beyond which interjection the mark being placed, the Bullet must be carried necessarily wide of the Mark on the contrary side to the recoil of the Piece.

Fig. 2.

Let $ad=a.$

and $dc=r.$

and therefore $ab=r-\surd :r^{2}a^{2}$

Therefore $ab.ad::r-\surd :r^{2}a^{2}a::I.x$ (x being any given quantity.)

Wherefore $a=xr-x\surd :r^{2}a^{2}:$

and $x\surd .:r^{2}a^{2}:=xr-a.$

Therefore $x^{2}r^{2}x^{2}a^{2}xr^{2}-2xra+a.$

Therefore $2xra=x^{2}a^{2}+a^{2}$

Therefore $axr=ax^{2}+I$

Quod &c.

f e k = f l p = p h m = the Angle of Recoil p h n the Angle of Reflexion made at the parting of the Bullet from the Piece. When p h n > p h m (m h being always parallel to f g) then must h n intersect f g if continued.

Some other Experiments I have also made with another Piece (about the same length, but of a bore near two tenths of an Inch less) and ordered in the same manner; and do find, that with a small charge the Bullet is shot (thence too) wide of the mark on the same side on which the Recoil is made, and with a full Charge wide the contrary side.

Fig. 3.I caused besides two Pistol-barrels of about five inches long to be placed upon Carriages with four Wheels, and loaded with Lead, that they might not overturn when discharged, and both of equal weight, and an Iron Cylinder of the length of both their bores, and of the same diameter with a piece of Lead of weight equal to it. So that the piece of Lead affixed to either of these Guns (which of them I should please to charge) might equally poise the other with the Iron Cylinder. And thus indifferently charging either with eight grains more or less of Powder, and putting the Iron Cylinder home into both, the piece of Lead being affixed to that which held the Powder, and then both so set upon the floor, and the Powder fired, I could not thereby discover, that the charged Piece, or the other, either of them, did certainly recoil more or less than the other, they rather seemed still to be equal.

These few Experiments I have made since, the Barrel being first cut at the muzzle parallel to a vertical Plane passing the line CD.

 

B	48	0. 8	L	R	48	1. 2	L
B	48	0. 9	L	L	48	0. 2	L
B	16	0. 1	R	L	48	0. 3	L
B	8	0. 2	R
B	8	0. 0	N

pag: 233.