Don't claim to be an expert, but...
If you were to bring this up in the Big Game Reloading subforum rather than here in the nut house, you'd find that many of us regularly use 7mm-08 data as a guide for modern 7x57's. Alliant indicates 44 gr of RL17 for 2669 fps so you are pushing it beyond wisdom, you really should tone it down or switch powders.
But it is anything but weak, your acquaintance knows less than he thinks.
First, one must understand the differences between these two Cartridges.
The 7 x 57 has on average 4 grains more case capacity that the 08.
The 7x57 data runs at 51K psi, the 08 runs at 61K psi.
This reduced pressure in the X 57 is based solely on the fact that there are rifles out there chambered in the X 57 that cannot handle the same pressures as a modern day rifle like the 700.
By using 08 (61K) data in the larger cased X 57 (51K psi) you will most likely achieve the anemic 51K pressures of the X 57.
The OP is running a 700 action, totally capable of handling loads up to 65K psi.
The problem with exceeding the anemic low pressure load data for use in a modern day rifle is the lack of Pressure Tested Data.
But that's not the end of the world, many of us have to do the same with the 6.5 Swede, the 9.3 x 62, The 257 Roberts, even the 3006.
I check the OP's load in Quickload, according to QL, it is under well 65K, just under 60K for that matter.
