Sectional densities of .422/423 bullets from the Woodleigh site:

404 Jeffery .422"
35 350gr RN SN 50 .281 .293 1800-2600 1.128
33A 400gr RN SN 50 .321 .335 1900-2400 1.282
34 400gr FMJ 50 .321 .330 1.347
33B 450gr RN SN 50 .361 .360 1800-2300 1.416
34B 450gr FMJ 50 .361 .355 1.491

10.75 x 68mm .423"
36 347gr RN SN 50 .277 .290 1800-2300 1.116
36A 347gr FMJ 50 .277 .288 1.188

347/350 gr is SD .277/281

Below the optimum penetration SD of the .330/338 250 gr SD 328/313, .366 286 gr SD 305, 300 gr .375 SD 305, .416 400 gr SD 330, .422 400 gr SD 321, .458. 480 gr/500 gr. SD. 327/341.

All the usual choices are SD 305 to 340.

The .375 270 gr SD is .274.

Both the 10.75 with its 350 gr bullets and .375 lesser capacity cases with a 270 gr bullet have not reputable big heavy dangerous game reputations. One can see one possible reason for lack of penetration with their lower SDs.

The other possible reason is thinly jacketed SPs. Proper FMJs shouldn't have this problem. But still suffer a lower SD.

Using a 400 gr projectile for the .404 with good jacket and construction should remove any such issues. If sufficient velocity can be achieved.

The original .404 loading, 400 gr at 2,100 fps and the .450/400 NEs, 400 gr at also 2,100 fps, both have probably killed thousands of buffalo, elephant and other thick skinned game.

NO reasons the 10.75x68 with a decent 400 gr at 2,100 fps can't do the same.

I'm sure I've read of hunters using the 10.75x68 on Australian water buffalo. Also at least one magazine article. Just none of our Aussie NE members. Be good to know of their personal experiences.

The 10.75x68 cartridge is uncommon here in Australia. Far fewer rifles coming on sale or auction than in Europe. Why get a x68 when one can get the better .404, .375, .458 etc? There are some certainly around. Often at a better price.

Interesting that this was one cartridge used heavily by continental world hunters. No wonder there is so often French rifles from their colonial empire chambered in 10.75x68. in addition to the usual German and Austrian rifles.