One case - two bullets

[Ganderite]

If I show up at a CQB with a revolver, you will know why.

This was tried just for fun. i just used the loading data for a 230 gr bullet. Inverting the bottom bullet saved a lot of powder room.

I did the same trick with 38Spl years ago, with similar bullets. I don't recall them beings so accurate.

 

[Andy]

I might try this on 338 Lapua using 2x 250gr bullets

This can only be done with straight-walled cartridges (like the 357 Mag, or 45-70), or bottleneck cartridges with long necks like the old 43 Mauser. The bottom projectile must be held against the side of the cartridge (body or neck) for the entire length of its body, or at least the great majority of its body. All you're really doing is seating the equivalent of one long heavy bullet in 2-3 segments against each other - there are still limits.

The 338 Lapua has a neck only about 0.325" long, so the best you could do with two 250 gr bullets is have each gripped by about 0.160". Not only is that not enough, but the top bullet would give an OAL so long that the round would not chamber without an extremely long throat.

 

[44Bore]

We often used to load 2 or 3 round balls in the 45-70 with a thin card wad between them--worked really quite well in the Ruger single-shot rifles. We also used to load 2 120 grain full wadcutter bullets in the 44 mag with much the same results as the OP. We used to put a card cad between them also so they wouldn't stick together. Was lots of fun but not really practical except for close-range defence.