I was reading a bunch of different info most of which was third party input and that’s where the 20” came into play. I appreciate all the help this should be a good starting point.Different companies, different platforms, but I am under the impression that ammo companies used to use 26-28" barrels for testing back when longer barrels were in style. Now that shorter barrels are in vogue they're testing with slightly shorter. Federal uses 24" barrels for their testing, per the emails we traded back and forth. I wouldn't be surprised if Winchester is using a 20-24" to test their 223 ammo.