I started loading 130 TMK a while back for my 6.5 CM (because that’s what I could find and I bought a bunch)… I could get 2850 or so with good accuracy versus 2650 or so for the 140s. When I replaced that barrel on that rifle, I replaced it with a 6 CM because I realized I was basically shooting the same BC with more weight, more recoil and lower MV. I still have a different 6.5 CM, running about 2825 with 130s from a 20” CF… that’s a father/son gun that I’m comfortable taking afield. Lately, I’ve spent a lot of time thinking about how I ought to have built at least one bolt gun in .223 to shoot 77-80 grain bullets before seeing this thread today. Everyone likes validation, no?
Re: wind drift. I think what gets lost in the conversation is that it’s not the ultimate difference that matters so much as the difference when we biff our wind call. If you’re a +/- 5 mph scrub (this guy), it matters more than for a better shooter. Yes, I get that “lag time” and BC are important measures of “ballistic merit,” but it’s not the whole story. Factory 108 ELD-M at 2940 fps drifts 1.22 mrad at 1000 versus 1.16 for 140 ELD-M at 2700… meaning that if I really can’t call closer than +/- 5 mph the performance difference at that range is +/- .06 mrad… maybe that 2.5” difference matters, maybe not. I shot a basic rifle course recently alongside .300 WM, .300 PRC, and a bunch of 6.5 Creed… used the same wind holds as all of the aforementioned out to 1000.