You do if you are close enough, or scared enough, that A.T. grenade could have done serious damage to most any of the tanks in the field at the time. And considering one did not have to die in order to use it,(A.T. pole grenade,run up to a tank, and jab it with the weapon,) or the various magnetic/sticky bomb weapons, (run up to tank, hope it sticks to it, initiate the fuze and run like the devil) it is a pretty good idea, and the ancestor of the modern grenade launcher. which uses the same Hi-Lo pressure system, and does the same job. An extra ration of sausage and kraut for the inventor.
It’s getting ridicolous! Nobody shoots with a Pistol against a Tank!
Are you sure ? :rolleyes:, at list the Sturmpistole was a stand off weapon not like the HHL in wich you need to put it in the tank.
In any case the concept of a grenade launching, antiarmor small arms is not abandoned
look this Hecler & Koch H&K 69.
And this is the 40x46SR cartrigde loaded with the M433 hohlladung projectile, it penetrate 50mm rolled steel armor.
I think it works against soft skinned or light armored vehicles, but - unless you are a hero with a suicidial wish - shooting a Main Battle Tank with a 40mm Hollow Charge from a Grenade launcher … good luck! 
But i will ask if we got something like that here and if i can get my hand on it, then i will test it on a Hartziel in natura
The HL 62 you mentioned, was developed by Professor Dr. Gerloff of the Waffenakademie Brünn ( Czechoslovakia) for the SS.
He developed the both very successful AT rifle grenades ( SS Gewehrpanzergranate 46 and 61) for the SS and the idea was to use major parts like the warhead for a flare pistol version.
Some shouldt see service in the last days of the war. Even today little is known about SS ammo - they keep it secret.
The armour piercing ability was Panzerwurfkörper 42 = 80mm and HL 62 = 90mm
It wasnt possible to blow up a tank except you hit the tank ammunition. But a shot into the lesser armoured parts of the tank between the tracks or at the rear wouldt stop the tank, destroy the engine and may be lighted up the fuel.
Armor is armor, and in WW2 it wasnt the Chabham or other layered stuff used today, so that shaped charge, even though its not huge, would still perf most tanks. perhaps not the glassis of the largest tanks, but any hit on the sides, or back will make a hole, with the usual results. fire, secondary explosions, casualties of all kinds. The shaped charge is a freak of nature, and doesnt follow all the rules of the physical world.
In more recent times, The Israelis used a similar device, fired from the Uzi, and perhaps other weapons as well, against the tanks of the Arab nations, with telling effect. the small charges still had no trouble perfing the armor, and burning the tanks. With this type weapon, size doesnt really matter much.
The armour piercing ability was Panzerwurfkörper 42 = 80mm and HL 62 = 90mm
It wasnt possible to blow up a tank except you hit the tank ammunition. But a shot into the lesser armoured parts of the tank between the tracks or at the rear wouldt stop the tank, destroy the engine and may be lighted up the fuel.
Knocking out the tank, no more no less than the desired effect. 
Someone stated, that this gun looks quite like a AG36 - i agree somehow it looks similar ^^
Seems like a Leucht-/Sturmpistole attached to the barrel of a StG44 (the gun in the upper right hand corner looks somehow like an RPK-74, doesn’t it?)
Another picture - what are those guns called??? The gun in the middle left look like an HK MP 5 und the one beside it like an AKM 74
Click
I could be terriblly wrong but I think that composite images of leutchpistole and MP 44 are a funny fake.
I never heard or read an account of the use of that system by the german military in der Zweite Weltkrieg. The the normal rifle grenade launcher apparatus was the schiessbecher, firing cup.
Anothe nice piece of information :
Wurfkörper is the WK LP (Wurfkörper Leuchtpistole) P - Pz.
It was introduced for close combat to clean the tank and the area arround from enemy tankhunters.
It was loaded like a normal flare cartridge and fired ONLY from inside the tank through a pistol or flare port . The thick walled HE shell flow from the barrel wind of the wire and the pull igniter in the bottom of the shell ignite a 1 second delay element. The heavy explosive load and the thick walled shell gave a blast and fragments that sweep away all attackers. It is little known and was only given to tank crews who know to use them. The cartridge was marked in big letters - ONLY USE FROM ARMOURED VEHICLES.
new poster here, but I have a Kampfpistole Z and its ALL steel no alum or zink whatsoever(beside the grips) its a very heavy gun, would guess 3+ Lbs maybe more
this is mine, found in the bottom of a box of evidence guns in Elma WA
[IMG]http://pic20.picturetrail.com/VOL1600/691553/9227619/287483834.jpg[/IMG
You can see that anti-tank pistol in action, sort of. It’s starts 5 minutes 34 seconds into this clip.
Very good find, Thanks 
Image from the main site