What is an ‘anti-tank gun’?
If you are thinking PIAT, panzerfaust, or M1 bazooka then the effective ranges are 100m, 60m, and 100m respectively. An anti-tank rifle had a similar range (100m), and were largely ineffective against later tanks.
So the rules on the SWA cards are clearly nonsense. 1 hex is generally considered to be about 450m / 500 yards, so these weapons cannot operate over 3 hexes.
Anti-tank rifles were used from the start of the war, but none of the others were around until 1942 or 1943 (panzerfaust), so again the two SWA cards don’t make sense.
Okay, so what am I suggesting instead?
Here are two cards I have created:
Please let me know your thoughts about them - they are very much a draft and I am happy to adapt them.