08-11-2022, 12:48 PM
Dt219 Wrote:Ill just shoot for groups and worry what the sd is if I can get a repeatable group
Sounds like a plan to me. I quit sweating chrono numbers a couple of years back doing initial load workups. I have been shooting F class in competition for over ten years now and was and still am a huge fan of Erik Cortina. However as I said I no longer worry about ES/SD numbers. A few years back though I had switched my go to .223 bullet from 80 SMK's to 80.5 Bergers and pulled out the chrony to get a benchmark on velocity. I was shocked to find the ES above 100 and SD above 50, yet at 500 yards I was getting sub MOA 20 round groups. I did further testing with my .260 Remington with 140 gn bullets at 800 yards and found the same thing. I am not sure if barrel harmonics come into play there but after doing a lot of testing using a shotmarker electronic target and chronograph I am convinced that muzzle velocity and vertical points of impact at the target have no correlation at all.
Just as a sidenote with my AR's I am tickled to death with 1 MOA groups, I have never been able to get any of my AR's to shoot consistent groups below 1 MOA. If I can get 20 shots into a 1.5 MOA group I call it good. Consider this. The NRA/CMP AR Tactical class that the 10 rings are 2 MOA in size where the F class (bolt guns) 10 ring is 1 MOA. I will be testing a new bullet/powder combo in my Grendel this morning, as I am thinking of switching from F call to AR/TAC next match.