Yeah definitely go for the H&N smart shot copper coated lead BB's or the webley accu BB's. They are much better then the gamo lead balls and will perform better too. The gamo lead balls are too inconsistent in size and in the revolvers like the dan Wessons and pythons and peacemakers can get sick in the cartridges, due to some being slightly oversized.

The H&N smart shot and webley accu BB's are consistent in size and the Dame size as steel BBs 4.4mm, I use them in my guns if I need to in both revolvers and semi autos like the Kwc 1911, if you use them in a magazine like the Kwc 1911 that has a strong high tension bb follower spring don't fill the magazine to the max with BB's so the top and bottom bb in not under too much pressure, just like you was doing with your mak..
The webley accu and H&N smart shot copper coated lead BB's Will work fine in the luger.
ATB Marc