20mm antitank rifles with HEAT rounds?

[Anthony]

Originally Posted by Ulzgoroth

By TL8 and probably even the latter parts of TL7, you could have a LAW with a confined-space safe countermass rather than a shooter-cooking backblast.

You only need it recoilless if the round is heavy enough to cause a problem. While I'm not finding a HEAT grenade at the moment, the M443 HEDP grenade exists (though it seems to have safety issues) and can be fired from an M203 grenade launcher. Not that 2" penetration in RHA will do much to a current tank, but it's still the equivalent of about 8d(5) in GURPS.