Granted it is a small sample, and totally unscientific, but my Remington 30-06 is 60-90 fps slower than my Winchester 30-06. Both have 22" barrels. How much slower depends on the exact load, there seems to be a bigger difference the heavier the bullet. With 150's it is usually around 60 fps slower, with 165 or 180s closer to 90 fps.
I compared my Winchester to a buddies Remington 700 in 30-06 and his 165 gr handloads were 130 fps faster in my rifle than his.
And over the years I've ran across a handful of other posts similar to yours where others have observed slower than expected speeds from Remington barrels.
I almost never get the same speeds when comparing my loads in different rifles, 20-30 fps even from the same barrel length seems common and as much as 50 fps not uncommon. More than that is rare, but it does happen.
I don't know for sure, but suspect it has to do with tolerances of the chamber and barrels.
