Yup

In real life the 5cm KwK 38 cannot penetrate the frontal armor of the Infantry Tank Mk.IIA, aka Matilda II (A12).

The GURPS: WW2 book All The King's Men gives DR 300 for that frontal armor on the hull and 290 on the turret.

The 5cm PzGr 39 the Germans were using in Libya does 6dx6(2) pi++ with a linked 1d-3[2d+2] cr ex.

That will roll an average of 126 which will fail to penetrate the 145 DR the turret front is reduced to by the armor divisor.

This GURPS!

Likewise the QF 4-pdr on the Matilda worked against the Pzkw III Ausf G's DR 120 hul and DR 145 turret front.

The best 4-pdr round in the desert was the Shot APCBC/T Mk.I which does 6dx4(2) pi++ and averages a roll of 84 which should punch DR 168...  I say "best" but all of the AP rounds calculate to 6dx4(2) pi++ except the early AP/T Mk.IT which is what GURPS calls an SAPHE round doing 6dx6 pi++ linked 2d+1[2d] cr ex; that only punches 126 DR, barely adequate for the Ausf G.

The H has DR 230 in the front and rear and some of the G's were upgraded to the H standard by the Afrika Korps.

This GURPS!