Downrange, & trying to calculate the actual boresight distance using a non-standard method. Given what members have observed from their ARs w/ 14.5" bbls, what is the actual MV velocity I should expect from M855? 2900? 2970? Or less? If you have chronographed it, please @ least tell me if the # you give is corrected for the actual distance of the chronograph.
If I have to shoot this thing, it'll be @ all of 20 ft, & in the 70's. It's getting quite pleasant here @ night. Yes, I've checked the Ammo Oracle - it gives # for 16" bbls.
In general, M855 has a muzzle velocity a little under 2900fps from a 14.5" barrel, which is about 80-100fps less than from a 16"bbl. Somewhere at this site there was a ballistics chart for a few different rounds from 14.5", 16" an 20" barrels for comparison, but I don't remember where.
ETA I think this was it, but the pictures are gone for some reason.
Maybe someone should contact the site staff to let them know the images are missing, but I'm to tired right now.