The Weatherby is loaded to a higher pressure and the freebore does take more powder to get there. I have a long throated 7RM and it loads about the same as the Weatherby. Also at times R22 had lot to lot variations up to 20% difference so I always check a couple sources and average them.
I also have a 7mmRM with a longer throat that takes heavier powder charges than a typical 7mmRM. My 2,980-3,000fps load for the 160NAB and RL22 is right on top of Nosler's book max for the Weatherby version.
The variations in the manuals when comparing the two 7mm chamberings can be interesting. I noticed that Nosler shows only a 3.5gr water capacity advantage for the Wby when both are loaded with 150gr bullets (Nosler brass in the 7mmRM and Wby brass in the 7mmWby.) This is a 4.5% increase over the 7mmRM. However, looking at the Barnes #4 manual and 150gr data with RL22 like the OP was talking about, they show 63.5gr max for the 7mmRM and 74.5gr max for the 7mmWby. That's huge. Both were shot in Kreiger 24" test barrels with the 7mmRM making 3,018fps and the 7mmWby making 3,245fps. That's also a sizable difference, but to be expected for an additional 17.3% larger powder charge.
