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Hey all. While on a Vist to the replica HMS Amity in Albany, Southwest Australia I found a gun on display next to the ship.

As normal I pawed my way all over it and found some measure markings on the rear of the gun.

These were indented on the side. 

Is this for elevation adjustments or are these for some other purpose.

I have not seen these markings before


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I don't know, perhaps a reference for a sight setting device and sight. Or maybe it is one of those markings the gunner used for his own references. I always painted a red line on the side of every 40 MM gun that I had anything to do with, very few ever knew what they were for. A 40 MM gun is not designed to be re-cocked and a second try to set the round off using the firing pin, so the way to do it is not taught or approved. I did it numerous times safely. Before there was a need I tested each gun and its operating handle to find out how far it needed to be rotated to re-cock the firing pin, yet not begin opening the breach, that point was marked with my red paint. Had a misfire once on a forward gun of a newly recommissioned ship, LST 601', the crew was evacuated and I and the trainer stayed, he kept the gun trained in a safe direction and wore the sound powered phones, I  was there to make things safe. I requested permission to attempt to unload through the muzzle, received it, re cocked and fired the gun. Next thing I knew the Captain was asking me why that gun fired, I told him and he told me he had been to 40 MM school and what I had just done, couldn't be done. After my explanation, I continued and taught how to do it safely. I hated to open a breach on a misfire, my first was a 3" 50, waited the 30 minutes after the last attempt to fire it, it was a cool gun with no danger of cooking off the projectile. Opened the breach and carefully extracted the round, worked it down through the loader and careful passed it to the Gun Boss, 'a Warrant Gunner', he shook the round, flipped it over and thumped the primer with his cocked index finger, said 'faulty primer', then threw it over the side. So maybe you are looking at some marks left by an experienced gunner respected enough to be allowed to mark his guns as he found convenient. So until you find a better reference, just call those marks, 'Gunner's Tracks', they are stamped or carved in, not cast.

jud  :pirate41:

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Imagination runs wild within those romantics who have never done it. With the sails up and drawing, roll is shortened, dampened with much of it eliminated, so aiming aids were not useless at sea in those days. It took experience, good timing and skill to take advantage of such aids but aiming the gun at the end or beginning of a roll is a position the ship is in that is quickly duplicated or nearly so at the end and beginning of each roll. At cannon ranges, sighting during those times can be fruitful. Could not expect sharpshooter results, but your prospects of hitting what you wanted were greatly improved by employing a gun sighting device, be it the Mark 1 eyeball or mechanical. It was the Lock Time that caused the greatest problems while shooting from a moving platform, it was random up until electric primers were introduced. Also close to the sea, a wave can come up and catch the round, sighting might have been perfect, but the watcher sees a huge miss. Those marks appear to reflect the basketball trajectory of a cannon at very short ranges, that being the case, it would not surprise me to find that those marks were part of sight and used aboard ship, nor would I be surprised to find out that the target was not even looked at using a sight but the marks were in place so that all guns could be elevated uniformity in relationship to their bores and the battery Captain timed the shots using roll and experience to start the ignition sequence by shouting, 'FIRE'. 

jud  :pirate41:

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  • 2 months later...

Jud, thanks for all the good information. Although I didn't serve in the Navy I, for some reason, have always been fascinated by the Bofors 40mm, particularly

the quad mount. May I ask if the mount was being controlled by the director, did the director have control of all functions. Were the trainer and aimer just along for the ride?

I could never remember which those two did what.

Regards, Harley

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On Sunday, 28 May, 2017 at 11:45 AM, jud said:

I hated to open a breach on a misfire, my first was a 3" 50, waited the 30 minutes after the last attempt to fire it,

Know that feeling very well - had to do it a few times for the 20pdr Centurion Main Armament in Country there was no option to wait in the middle of a contact just open the breech slowly and very gently slide it out and throw it outside the turret through the pistol port. Then it was safe to breath again - load another round and back into it. cheers Pete

Edited by PeteB
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Hi guys, I concur with Druxey's observation - I have read in an Ordnance Handbook, or 'official' publication about ordnance being manufactured back in the mid-1800s - just cannot recall the publication at the moment (may have been Douglas but would need to check).  The author states that these barrel markings were only applied to naval style guns used in coastal defence.  

In this publication there is also some discussion about the use of Dispart and Tangent sights (introduced by Miller for naval guns) so may have been in relation to the fact that such marks were unnecessary given these sights (this my interpretation as there is no clear relationship implied nor discussed in the book).

If the factory/ordnance authority publish such a statement it is good enough for me :) 

Even with such sights, the lock issue as Jud describes was the major problem.  This lead to the introduction of the gunlocks at about the same time, or just a little later.





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tagerdvr; Never was around a quad 40, singles and twins. The Bofors, both single and twins I was around were manually fired by the right foot of the Pointer on the gun, he was often the gun captain because it saved one man for something else and a well trained gun crew worked that with no trouble other than preventing the gun Captain from moving around. On the LSTs I was aboard we had MK 51 directors which were gyro lead computing sights with a station for a man to manually crank in the range which he received from the sound powered phone system, not firing key on the director, the gun followed the director and the firing was by voice command. One reason I loved that Bofors was other than for training we left the covers on the directors and the pointer and trainer controlled the gun. Other ships, other guns, my experience with 3" 50s and 8"55s had all the options and director choices and controls running through barrel switches.


Need to do some rethinking about the Power drives and firing circuits on the Bofors, we didn't use them in RVN, but they were set up for director control against aircraft and surface targets. More details will probably come trickling in overnight and I can make some corrections and additions.





Edited by jud
Needed expanding and corecions.
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  • 3 weeks later...

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