So I got a Nikon m-223 for my wifes AR thinking that this would be a great stater scope for her to get into shooting long range. I didn't do too much research before I bought it. After mounting it and doing some reading on it, I found that the velocity were off. The scope is rated for 55gn vmax 3240 fps out of a 24" barrel. The rifle it is on has a 20" barrel. I tried out the Hornady 55gn over the chrono and got an average fps of 3000 which made the adjustment off. As per the hornady this ammo is rated as 3240fps out of a 24" barrel so they are not off. After runs some numbers through the ballistic calculator and nikons app for there scope (Nikon Spot On™ Ballistic Match Technology Program). I found that a 50gn vmax traveling 3300 fps will have almost identical ballistics as the 55gn vmax @ 3240. I used ramshot tac powder with 27.5gn (this is .5gn over max) and was getting avg 3320fps which grouped about 3/4" at 150yd with my shaky hand. I have to load up some more round and go out to check the adjustment but it is looking really promising to get the right ballistic for the scope with a 20" barrel. Hope this helps the people looking to get the scope or having the same problem as me.