Turkey adopted the 7.65 in 1890, immediately after Belgium. They used it through the Great War in all those 1890 Mausers as well as the 1903 short-action models. These rifles mostly were converted to 7.92x57 in the 1930s.
In every case, the cartridge casing was identical, only the load being changed around and, often, not much at all. In those days it was very fashionable for every country to have their own 'special' cartridge, just to show that they knew more than the other guys. In fact, although the receiver crests were different, all the rifles were made in the same plants, rifled on the same machines and almost all with the same pitch, so the loads actually were pretty close.
The rifles all were Mausers of one model or another... 1889 Belgian, 1890 Turkish, 1891 Argentine to start and the others followed on later.... 1893 Turkish, then the Paraguayan(?) and so forth. The round was loaded with a variety of bullet weights at varying velocities. Nice thing is that the only part which needed to be different was the ramp for the rear sight... and that could be changed out in an armoury in an hour if you had the tools and some experienced people.
Ballistically, when using the original 174-grain bullet, it duplicates the .303 Mark VII Ball round. Early loads with heavy bullets tend to duplicate the early 215-grain 303 loads. Essentially, it is a rimless .303 and runs at similar (low) pressures.
It's a nice cartridge and it was decades ahead of its time. If you load it with a 150, it can duplicate the famous and world-beating 7.62x51 NATO, just that it did it 60 years earlier. There is only 2mm difference between the NATO and the old Mauser rounds. Why NATO didn't just go ahead and use the 7.65 is beyond me; they even could have freshed-out old .30 barrels and made it work. Guess there wasn't enough money running through it that way. Besides, the T-65 was an AMURican design and so was/is automatically better, even though pressures are much higher than with the 7.65. You can make 7.65 brass a number of ways, as has been detailed, but you can also blow out fired 7.62 NATO/.308 Winchester (if they are held by the extractor) and they will lengthen pretty much to spec in a couple of firings: cheap.
Hope this helps.
.
