18" or 20" 260 Upper

[rowcifer]

Looking at a 260 upper either DPMS or custom build with an 18" or 20" barrel. About what could i expect for velocity using 123 or 139 gr Scenars with either barrel legnth?

 

[Rovieairto]

Re: 18" or 20" 260 Upper

139's around 2600 ft/sec at 20"
123's 2825 ft/sec at 20"