QuickLOAD calculates ~2,500 fps from 52gn IMR or H4350 in a 23.75" barrel, and that's pretty well what I'f expect. That is expected to run at 49,000 psi or thereabouts. The 7.92X57mm IsS is a powerful number and CIP maximum is 56,565 psi, so in theory 2,700 fps with a 200 might just be 'on' using a very high energy powder, to wit Alliant Re17.
The WW2 sS (Schwerer Schpitzgeschoss or heavy pointed bullet) loading was developed as a machinegun round and was found to produce excessive pressures in the G98 rifle and its inter-war successor, the KAR98b (which despite the use of the KAR = Karabiner = carbine designatgion was a long rifle with 29.13" barrel, in fact a slightly modified development of the WW1 Gewehr '98). As a result, rifle chamber throats were redesigned to reduce pressures.
As adopted, the sS round nominally gave a 198gn Tombak-plated steel jacket and core FMJBT bullet 2,575 fps MV at 46,926 psi average chamber pressure, but note that MV was from a 29.13" KAR98b barrel, so the the nearly six inches shorter KAR98k barrel will produce a fair bit less.
Powders have moved on a great deal from the 1930/40s, so 2,500 fps in a K98k is in line with historic performance. Whilst I'll happily accept you got that with your rifle and 50gn Watercam, I don't see an extra 2gn taking it to the maximum listed load producing an extra 200 fps or 100 fps / gn powder. QuickLOAD says 50 fps / gn for H4350 which seems about right for the powder and bullet combination.
Going back to my days with 7.92X57 many, many years back in a Portuguese M1904 'Mauser-Vergueiro' in very good condition and an absolutely mint 1944 Brno KAR98k that looked like it had never been shot, I must say I'm full of admiration for you guys. 2,500 from the 200gn SMK - that's a punishing combination in these rifles. One aim of getting the 1904 Portuguese rifle (strictly speaking, these cut-down and rebored 6.5s were designated m/904-39) was to use cheap Yugoslav ammo (headstamp looks like nny, but that's Cyrillic for ppu - it's old Prvi Partizan military spec) that was available in the UK for around £12 / 100 at the time. That plan lasted one range session and maybe 20 rounds and I went out and bought a set of dies. Attempt 1 was to download the ppu stuff - square flakes like you found Canuckstein - but anything more than a 5% reduction performed very badly and dirtily, so it was onto a mild load with a light (125gn ?) Hornady flat-base SP bullet and that was very nice for short-range and accurate enough too. I had a lot of pleasure from the 1904, not nearly as much from the K98k for some reason which soon went.
Incidentally, QuickLOAD says 47gn IMR-4064 with the 200 SMK at 3.17" COAL (military 198 sS standard) gives 97.1% fill-ratio, 52,300 psi PMax for 2,536 fps in a 23.75" barrel. That's using the program's default case water capacity which I've no idea how accurate that would be against what you're all using.
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and a Type 99 Arisaka. The bores are pristine after slugging the I know why they were sporterized. To many projects not enough time or money. Next will be a LR rifle built on a ARC receiver. Now that I have finished my MK-12. But thats other topics for another time.
