I'm shooting a 20" Mosin M44 (made in Poland) with a scout rifle 2-7 scope setup. My current handload is a .311" Sierra 150 gr bullet over 48.5 gr of IMR 4895, which is a max load in most manuals. Load shoots close to MOA for 3 shots. When I shoot PPU 150 gr soft point factory loads they're a lot less accurate, but they make my handloads feel like managed recoil loads. The PPU loads hit 4" higher at 100 yards and has significantly more recoil and muzzle blast.

My question is that US reloading data is really conservative?

more of a question of what powder they may be using, along with the powder they might be using, which is canister or not available here. They could be using a powder that is faster, but using less of it..

I don't use H 4895 for reduced loads, as I don't find it that accurate, yet it has a much larger retort when you pull the trigger, that does using IMR 4895 with the same reduced charge weight, and IMR 4895 is much more accurate with reduced loads, vs H 4895.

For reduced loads, you can use either 4198s, ( I prefer IMRs tho), or RL 7, obtain the same velocity, with less powder.

I have used some different powders in reduced load ammo, and even tho they are faster powder, their point of impact is higher and sometimes several inches ( to include 4 or 5 inches @ 100 yds) than regular powered full loads,

A lot of variables on what and why you are seeing it. I'd disassemble the PPU load ( one cartridge) and see what their charge weight is.

These are generalities I've seen, but there are too many variables to tell you what it is.

I think it would behoove you to widen your library of reloading data. Comparing Vihtavuori (CIP data) and Lyman 50th edition (SAAMI data) I'm only seeing 25 fps difference in max loads for the 150gr...both test rifles were 26 inch bbls...they are showing just under 2790 fps. If you are going to stay in the hobby, you may want to think about a chronograph....when you stray off the reservation, the chrono is your most valuable tool.

I should have noted that my 150 gr Sierra load chronos 2600 fps +/- from the 20" barrel.
Next time I get out the chrono, I'll check the PPU load.

There's an article by Mike Venturino in December 2013 Handloader that may be of interest to you. I just scanned through it the other day. Not sure if it addresses your question or not.