6.5 Grendel Velocity..What is realistic?

[Harpoon1]

As to barrel lengths, if we look at 1 bullet (123gr SST) and compare from 10.5” to 24”:

10.5” 2200-2250fps 260-270yds expansion, 225yds PBZ, 875yds supersonic
12.5” 2280-2350fps 300-350yds expansion, 240yds PBZ, 900yds supersonic

14.5” 2350-2420fps 350-400yds expansion, 240yds PBZ, 950yds supersonic
16” --2420-2470fps 400-420yds expansion, 250yds PBZ, 975yds supersonic
18” --2450-2500fps 410-440yds expansion, 250yds PBZ, 1000yds supersonic

20” --2520-2590fps 450-490yds expansion, 250yds PBZ, 1050yds supersonic
22” --2550-2620fps 475-525yds expansion, 255yds PBZ, 1075yds supersonic
24” --2590-2640fps 500-520yds expansion, 260yds PBZ, 1100yds supersonic

I see you’re in Utah, are those Supersonic numbers for your local “avg” density altitude? Or adjusted for a standard day @ sea level?