Kiwi bloke - Ed Matunas did quite an extensive article on .270s many years ago. He used 5 or 6 different rifles in his test and found our exactly what you are referring to - very much sub-standard speeds - but usually only with 130gr bullets and only in some rifles.

He found velocities from 2,740fps up to 3,150fps with the factory ammo & all in factory rifles with 22" bls. - and with a variety of 130gr. ammo at that. WW, Fed. or RP (1 of them) told him they hated loading 130gr. due to this wide range of speeds form seemingly normal rifles and Ed noted that might be why some people swear by the .270 and others swear at it. (I like to sear at it, but I've never had one - HA! Elmer taught me to do that - maybe the one he tried produced sub-standard ballistics?- or maybe it was just Jack O?

Ed found loading 150gr. in factory or with handloads eliminated this "slow trend" of some rifles & brought them all up to standard speeds and suggested those shooters with slow .270's use 150gr. bullets instead of the 130's.