Yes it is exactly because of your barrel. Most ballistic charts are created from 24-26" barrels not 20". So if the box say's 2650 FPS then it's probably 2400 out of your 20". That is why factory ammo sucks for anything other than plinking. My first thought was wow your groups are terrible. I would not be happy with 3 MOA at all. But then again for cheap factory ammo it does the job intended. It is Minute of Deer...or Man which is what you should expect for the price.

Hand loading offers so much more in the way of accuracy. Not just in picking the bullet but also in tweaking the charge for your rifle. The factory will always be conservative and on the low side of the charge ladder for liability reasons. Every factory round I have chronoed has been well below their stated speed. For example I load my 175g SMK round to 2620 in a 20" barrel and 2850 in a 26" barrel a full 200+ FPS more than any factory load and much more consistent. My 150's run 3000 FPS!. You can't even compare it to factory. Once you shoot hand loads you only see factory ammo as a source of brass.