British 4.2-inch Heavy Mortar

[horsa]

Shot below for reference shows three mounts with the first being for the 3-inch mortar, middle one is for the lightened 4.2-inch mortar and the third one being for the towed 4.2-inch mortar.

The lightened version would appear to be based on the standard 3-inch format with the addition of a third leg, third leg locking bar which might not be visible in the shot and of course the cradle for the larger 4.2-inch barrel. Worm gear seems to be the same on each of them. There are differences in the locks for the standard legs on both mounts but I think that is a difference found in early and late 3-inch mounts and not something to differentiate the 3-inch vs 4.2-inch patterns.



Nomenclature is not official as I don't have a manual handy so hope you can decipher what I'm calling things in this post.

[wally2960]

Thank you David, for the information. Here is a picture of my tripod and I believe it is a different version of the lightened version in the middle of the shot. Now I'm started cleaning it and to remove all the rust and red paint. I found some markings refering to the manufacturer. It seems that it was built by J.C.L. in 1942 and broad arrow.
For the restauration I search exact mesurements for the barrel because the possibility of finding an original barrel will be very small, so I want to make a replacement but therefore I need the length of the barrel. greetings Wally

here the link to pictures

http://brechtsoorlogsmuseum.freeforu...-inch-t12.html

[horsa]

That mounting in the center is one I borrowed for comparison to my others in the shot so I don't know it's history. But it is marked 4.2 and has the Australian D/|\D markings on it with a 1943 date. I'd say the one you posted is virtually identical though. Could be yours was an earlier produced 3" mount that was modified to the 4.2" format as those bigger mortars were coming on-line since it has a 1942 date.

For the barrel, the length of the smooth bore pipe is 60 inches with a muzzle outside diameter of 4.75 inches. The first 18 inches from the breech end has an outside diameter of 5 inches.

[wally2960]

Thanks for the detailed mesuraments and the quick reply. I have another question concerning my restaurationproject: which kind of sighting were put on the mortar? After some detailed examination of the wartime photo's I can't see much difference with the 3 Inch mortar sights. Was it common to put 3 Inch optics on the 4.2 inch mortar? greetings Wally

[horsa]

There were two main types of sights used and after the 4.2" mortars got into general issue, it seems they changed the data plates on them to read something along the lines of 3" and 4.2" mortar. The biggest visual difference on the two patterns is how they connect onto the mortar mount. One type has a socket and the other type has a dovetail. In the shot I previously posted showing some mounts, the center one uses a socket type sight and the other two have dovetail mounts.

I can try and get photos of both patterns sometime over the weekend if you need them.

[wally2960]

Hey David, I would be very interested in some pictures of the correct mortar sights used for the 4.2. It seems that my mount was equiped with a cradle of the socket type. Unfoutunatly the socket have been broken off since warend. While cleaning I noticed on the cradle two bolts near the outher edge of the cradle, not far from the socket. They also are present on the wartime picture placed on my forum. Do you know of what use they were? I've posted also new pictures of the cradle (with visible bolts).

http://brechtsoorlogsmuseum.freeforu...-inch-t12.html

[horsa]

Shots of the two basic types of sights used during the war. One on the left has the dovetail and the one on the right has a socket mount. Your mortar mounting used the socket type.





The bolts you were talking about are hard to figure out from the angle. With the cradle and sight adjustment area being incomplete, it could be that someone added bolts to fill the holes.