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Help No68 anti-tank grenade

Listy

Well-Known Member
I'm working on a book at the moment, and it'll be touching on early hollow charge developments. Obviously the No68 grenade is one cracking example of how not to do it. Trouble is I'm having trouble finding a copyright free picture of one, and its liner.

Now I did think of buying one, as there's a few available at the moment, however most are drill rounds, and the one which doesn't, and has its liner is nearly £300. I can get a No68 (drill) and a another shell type that I need for that.

So in lieu of anyone knowing where there's a cheap No68 that matches my requirements, might I enquire if someone with said projectile is willing to take some photo's for me and let them be used in a book?

Thanks,
 
Herewith a couple of photographs, my copyright, that you can use. I am intrigued by your 'how not to do it' remark and would appreciate some expansion. The No 68 grenade was, as I understand it, the first production munition employing the hollow charge principle and probably deserves to be cut some slack on that fact alone.


No68Thorpe.jpgNo68MkI.jpg
 
Herewith a couple of photographs, my copyright, that you can use. I am intrigued by your 'how not to do it' remark and would appreciate some expansion. The No 68 grenade was, as I understand it, the first production munition employing the hollow charge principle and probably deserves to be cut some slack on that fact alone.


View attachment 159465View attachment 159464



Thanks!

"how not to do it" comes from a few things I've spotted.

Cone is made from steel, while less of an issue it is sub optimal. Add in it has a base fuse, with no stand off. While officially, yes it can penetrate 2in of armour, tests showed the behind armour effect of these penetrations were negligible, if you wanted a meaningful effect the penetration was much reduced. Finally there was the issue of aiming it. It generated so much pressure in the gun the recoil was much increased to the extent it'd break your shoulder. Equally, the gun barrel had to be wrapped in wire to prevent the barrel splitting, although this may have been the case for all the rifle grenades fired by the SMLE cup discharger.

But the recoil problem was present in the shoulder launcher they designed for it as well. You've got to love any weapon where the design brief starts off with "Work out how much force a shoulder can take before it breaks, and make the weapon just a bit less than that." Then work out all the stats from the weapon from that point onwards.

edit:
Just looked at the black thing, what is it? some form of prac or drill round?
 
Cone is made from steel, while less of an issue it is sub optimal. Add in it has a base fuse, with no stand off.

Steel was fine. Steel liners were used in the US Bazooka rounds and the German Panzerfaust, amongst others. While copper might be easier to machine, the metal for the liner used is largely irrelevant. For the two phases of attack - formation of part of the liner into a jet, and forcing aside the target material by the extremely high pressures (greater than 300,000 atmospheres even back in the 1940s) of the jet - "theoretical calculations are based on classical hydrodynamics of perfect liquids because the strength of the metals involved can be neglected at the high pressures encountered"*

Tests with the No.68 with conical liner, which had about a 2cm standoff, showed it could penetrate 44 mm at normal and 37mm at 30 degree Beardmore armour plate, which was more than sufficient for side attack (and even frontal attack) of known potential enemy AFVs (German, Czech and Italian) in existence at the time of its invention. As a novel and groundbreaking use of the shaped charge effect in an infantry weapon, which one way or another helped guide future designs, it was a valid development, too easily dismissed with the benefit of hindsight.


* "Explosives with Lined Cavities", Birkhoff et al, Journal of Applied Physics, Vol. 19, June 1948.
 
Steel was fine. Steel liners were used in the US Bazooka rounds and the German Panzerfaust, amongst others. While copper might be easier to machine, the metal for the liner used is largely irrelevant. For the two phases of attack - formation of part of the liner into a jet, and forcing aside the target material by the extremely high pressures (greater than 300,000 atmospheres even back in the 1940s) of the jet - "theoretical calculations are based on classical hydrodynamics of perfect liquids because the strength of the metals involved can be neglected at the high pressures encountered"*

Tests with the No.68 with conical liner, which had about a 2cm standoff, showed it could penetrate 44 mm at normal and 37mm at 30 degree Beardmore armour plate, which was more than sufficient for side attack (and even frontal attack) of known potential enemy AFVs (German, Czech and Italian) in existence at the time of its invention. As a novel and groundbreaking use of the shaped charge effect in an infantry weapon, which one way or another helped guide future designs, it was a valid development, too easily dismissed with the benefit of hindsight.


* "Explosives with Lined Cavities", Birkhoff et al, Journal of Applied Physics, Vol. 19, June 1948.

Thanks, I thought steel was less effective as a liner, as they switched to coper for the MD1 bomb, but then back to steel for the PIAT and got a small reduction in performance.

However, as I said maximum penetration was not as much of the question, it was the effects after you'd put a hole through something. MD1 found from testing that the No68 had a pretty poor penetration if you wanted to kill anyone or cause any damage inside.

Of don't get me wrong, I like the grenade and the idea (hell I just brought one). But there are flaws in the weapon.
 
Listy,
Thanks. The black thing is an experimental anti-tank and anti-personnel rifle grenade based on the No 68. Almost all plastic it could be fitted with a fragmentation coil or collar. The project had a very limited life.

The other photo shows the first Service Mark of the No 68. Six Marks were produced, the first two of which had brass liners (albeit hemi-spherical rather than cone shaped) and trials were done to increase the stand-off. Surprisingly the grenade lasted to 1943. I looked at the training manual for the grenade and its author agrees with you, the recoil is 'considerable' although he does go on to say that the rifle butt should be placed against a sandbag!

Good luck with your book.
 
Listy,
Thanks. The black thing is an experimental anti-tank and anti-personnel rifle grenade based on the No 68. Almost all plastic it could be fitted with a fragmentation coil or collar. The project had a very limited life.

The other photo shows the first Service Mark of the No 68. Six Marks were produced, the first two of which had brass liners (albeit hemi-spherical rather than cone shaped) and trials were done to increase the stand-off. Surprisingly the grenade lasted to 1943. I looked at the training manual for the grenade and its author agrees with you, the recoil is 'considerable' although he does go on to say that the rifle butt should be placed against a sandbag!

Good luck with your book.

*scribbles furiously* uh-huh, I knew that.

Seriously, thanks for filling in the blanks. I only touch upon the No68 as the start of PIAT story, and how it effects the Bombards story. But its a tidy little weapon, and an ok idea, just not one that worked. Found these illustrations online on ideas and ways to fire the No68, and use it as an anti-tank weapon.
7O9PdGT.png


2r4KxC4.png


Also thanks for the words on the book, but If I can match my book that came out this month I'll be happy, that seems to be doing really well!
 
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