best way to tune SD/ES

[JohnMill]

One little thing I haven't seen mentioned here is a barrel mirage/heat shield. Barrel heat will give you those 3 and 2s a lot.
Many years ago someone did a study that showed that (bare) barrel heat would begin to distort the image in the scope at/by the 3rd shot. It was slight enough that the shooter couldn't detect it. It was measured optically. This is all from memory and remember, memory is the least reliable way to remember stuff

John

 

[RonAKA]

One little thing I haven't seen mentioned here is a barrel mirage/heat shield. Barrel heat will give you those 3 and 2s a lot.
Many years ago someone did a study that showed that (bare) barrel heat would begin to distort the image in the scope at/by the 3rd shot. It was slight enough that the shooter couldn't detect it. It was measured optically. This is all from memory and remember, memory is the least reliable way to remember stuff

Good point. I have noticed that mirage for me has become intolerable as of late. It was probably affecting things well before that. Shooting in cold weather and dead calm for wind seems to make it much worse. Used a discarded valance for vertical blinds to make a shield. It is 3.5" wide and seems to work well. Just attached it with Velcro.

 

[JohnMill]

I was reminded of the barrel mirage Thurs after I had fired half of Steckers tips for VLD etc. (had to be reminded of that too), 12 shots in a hurry as the rain was coming. Toward the end the scope appeared to start "winking" and that was a sure sign of heat. The barrel appears to release the heat in bubbles so that at times the image is blurred beyond use. I don't think the "bubbles" are physically possible but that's they way it looks,
I have used plastic and metal Phoenician blinds and the little blue foam thing that Home Depot sells for insulating overhead range hoods. I'm pretty sure Sinclair sells a kit and Watson used to, though I think he has left us.
We used to sit down with a 15 round block and shoot 3 groups sometimes different powder charge,seating depth etc., and you could throw out the 2nd and 3rd group if you didn't shield the barrel.

John

 

[AdamJ]

found a load that works good on paper and over the chrony. 32.0 grs BM, cci br-4, 68 berger jumpin 20 thou. 3460 fps ave, low teens ES, SD in the 5s, and shoots into the low .2s. I might try some lighter bullets62-66 gr see how they fair I have noticed the mirage more lately in the cold weather then at anytime this summer. Could be the scope am used to 14-24x topend and am running a 32x sightron s3. Definately need to look into a mirage shield. thanks for all the help