Hi guys, I recently picked up this pair of plates and have been trying to work out what hit them and under what circumstances. They do 'fit' together so I am sure that it was only one impact shown across both plates. The impacts looks most like a HESH round has struck them but it looks to be a fairly small calibre and the plates themselves a I think too small to be on a firing range, perhaps a controlled test/lab situation? Any suggestions would be welcome, I also understand that this is post war so mods may want to relocate this. Many thanks.
Looks like a 4in/100mm calibre impact. All depends on how much the calibre relates to the impact crater. I know the person who might have the answer to that...
A 76mm HESH squashing to around 100mm diameter seems plausible. Perhaps it was a test of HESH v spaced ar Youtube came up with this as a comparison:
I'm going to say it's a 120mm HESH. Asking my expert friend he said that generally HESH craters are either the same size as the projectile, or a bit under it (which is not what I was expecting). Equally, there's a lot of damage for a 76mm HESH round. But ultimately,that's a guess.
I know I'm picking this argument with the wrong person... My oft-quoted yardstick is the spigot mortar's 20lb A/Tk round's performance of blowing a hole clean through 2" armour plate. That was an 8lb-ish charge. I don't know the charge weight of 120mm HESH but I'd like to think it would perform better against a couple of 20mm plates if it was intended to upset MBTs (I know actual penetration wasn't the point). Scaling up from the video, a 'couple of handfuls' seems consistent with the damage and what would fit in a 76mm. Am I right in thinking there's only a choice of 76, 105 and 120 for in-service HESH? Hmm... will have to check the 20-pr.
The crater being smaller than the calibre is interesting, I suppose it depends on how much it squashes before the explosives are detonated? This also raises the question of circumstances as these seem very small plates to be firing 120mm ammunition against I think the Cockerill 90mm also has a HESH round, although not in service with the British.
Dug out my 120mm HESH drill round from the Wombat and offered it up to the front plate, it fits quite snuggly.
My nerdiness spreads... 9lbs of PE filler. And checking my notes, it seems the assumption of the crater being the same size as the projectile is incorrect. Bombard round against 40mm plate at 30 deg slope: Front damage: 7.9”x8.6”. Rear damage: 14.6x15.3”. I wonder if I've got L5 DP damage tables somewhere. I will have to go check.
I know a chap that used to do impact inspection on warships. Live testing against hulks etc. His opinion on being able to tell with certainty what made the larger holes/craters from 'conventional' shot without the thing still being embedded was 'nah' unless you knew what had been pinged that day (or, presumably, what an enemy shooter was likely to be using). Mostly pointy lumps of metal making mostly pointy or smashy holes of infinitely variable diameter & angle in an equally wide range of possible materials. I can see how that might be different with 90° test shots. Just a passing thought on this stuff in general. (Took me a while to process that the 20p sized holes all over that colander Grant were from strapped on Panzerfaust warheads. Six of us, & nobody guessed right while staring at them. Then the owner who did the strapping strolled over to explain. Physics is odd.)