I have not done a technical article for a while, so I'm afraid today's one will be. No stories of daring do today, but normal service will be resumed next week. Sorry if its all a bit boring.
This all came about due to Silentstalker's recent post on the “For The Record” blog about the Armoured Vehicle Royal Engineers (AVRE) tanks. In that article Silent cites me as a reference, but unfortunately he got a few bits and pieces wrong.
Let me hasten to add, this isn't his fault though. He was citing some research I had posted, and I'd gotten some stuff wrong, mainly because of confusion in the exact details (which I will explain later). Chatting to Silent he's suggested I write a piece explaining the ins and outs of a subject he's not fully up to speed on, so here is a more detailed version.
So we'll start in the Second World War. In February 1943 at Hankley Common, a pair of modified Churchill tanks were trialed. To one of the Churchills was fitted a deployable armoured screen that allowed sappers to work under cover and use explosives to demolish a concrete wall. The other tank had its gun replaced with a 290mm spigot mortar. These ideas were refined and built into one hull and became the Churchill AVRE we all know, which served throughout the war. The success of this vehicle cemented the idea of the AVRE in the minds of the British military.
The US developed two guns from the BL 6.5" Mk I. These were the 165mm T156, which was essentially the same as the British gun, although it did have some minor alterations. Then came the 165mm M57, which was the production version of the previous gun.
Now we skip forward to 1962, and the first prototype of the Centurion AVRE. The Centurion AVRE first entered service in 1963, and eventually replaced the FV3903 entirely in 1965. The Centurion AVRE was armed with a L9A1 165mm gun, which could fire a 64 lbs shell. Its a sign of how far technology had come, as about 60 lbs of that is reported as plastic explosive (more on this in a moment). The L9A1 fired its shell at a higher muzzle velocity than the previous BL 6.5" Mk I. Interestingly the L9A1 could also fire the earlier 6.5" shells as well.
So why the confusion? Well the US brought the L9A1 for their M728 Combat Engineer Vehicle. As before they tweaked it a bit so it was different and called it the M135. But, and this is what is catching everyone out, they continued to fire the old 165mm ammunition that the M57 gun fired. The round fired by the M57 gun, appears to have been a modified version of the 6.5" BL MKI round. With about 30 lbs of explosive in the warhead. The US designated this the M123 HEP.
So this leaves us with a slight issue. There's plenty of authors who give the weight of about 30 lbs of explosive as the L9A1's warhead. They could be right, but they could be mistaking the L9A1 and the M135 shells as one and the same. Of course 60 lbs seems an awfully high percentage of the shell to be explosive.
Next week we're back to normal, I've got a story involving tanks, heroics and horses, and a battle most of you may well never have heard of lined up to tell you.