Operating Manual for 80pr RML Gun.

by John

One of the Armstrong rifled muzzle loaders at Warrnambool

The manual/handbook is undated, but it was printed for the Warrnambool Battery, and lists the iron carriage and slide, so that dates it after 1875. Before that the slides were wooden.

The following is my precis of the interesting specifications. A full copy of the Handbook is available on request

The weights given are: barrel 80cwt, carriage 41cwt, slide 74 1/4 cwt. So, the total weight of the cannon = 195.25cwt = 9.92tonnes (9.76 UK tons). That is the only document which I have discovered which specifies the overall weight, it is interesting to me because it explains why my model weighs close to 10kg. 10kg is close to 1/1000th of the full size weight, which is what is predicted from the model 1 in 10 scale!

Other specifications include: calibre 6.3″; total length 9’6″; 3 rifling grooves with a twist of 1 in 35 calibres, vertical vent 6″ from end of bore.

The sights are located only on the right side, and the tangent site is angled at 2º to the left. (to compensate for the projectile deviation resulting from rifling).

The hydraulic buffer piston had 4 drilled holes. The diameter of the holes was determined by test firing. The cylinder was filled with SOAPY WATER, (not Rangoon oil, which other cannons used).

The slide is of iron, except for the top ‘T’s which are steel.

The brake band permits the carriage to run back, and tightens automatically after recoil to retain it. A hand brake lever controls running up. (? should be running down?).

Barrel elevations: 5º down, 30º elevation, 19º down for loading. (Oops. I had set 17º as the loading angle. Hope that is not a hanging offence)

Charges: Full 20lbs; reduced 16lbs 12lbs, saluting 8lbs.

Projectiles: Studless. With gas checks. (which is further evidence that the manual is post 1875). 80-86lbs,

Fuzes: Percussion or timed (15 seconds).

Penetration of wrought iron plates: At range 0 – 8.5″; range 1500yds – 6.75″; 3000yds -5″; 4500 yds 4.25″.

The manual then lists the procedures for the gun crews. I will summarise those in the next post.

Page 1 of the Handbook for 80pr RML GUN.

with grateful thanks to Marten Syme, historian, for sending me a copy of the handbook.