6br load development 100yd vs 300yd results. Need guidance.

[MS50]

I am doing load workups for a new McGowan 6br, Savage Mod12 action, no turn chamber. I have been reloading for 2 years. I found that my 223 and 308 100yd nodes work well at 300yds and beyond. This is not the case with the 6br. I found .3in nodes at 100yds using 87gr Vmax (3040fps), 105gr Amax (2905fps) and 105gr Match Burners (2880fps). These are all .005 off the lands. These loads shot between 2.3in and 3.0in at 300 yards. I believe my 300yd technique is good, as I shot a .5in .223 55gr Spitzer group under the same conditions. The brass is new Lapua that I am forming to my chamber as I do the load workup. I am using a .266 bushing after running a mandrel through the neck and chamfering the mouth. Outside diameter of my loads is .268. My question is where should I start first to improve longer range accuracy? At this point, is seating depth more important than MV and neck tension? Primary use for these loads will be steel targets out to 1000yds. Thanks for any feedback.

 

[DeltaBravo]

In my Shilen 8-twist .270 neck 6BR it liked to have the 80 grain FB Bergers at touch. With my 14-twist .266 neck, it likes to have the 68BTs 9-thou off touch. I'd work a little more on the seating depth, assuming the powder charge is optimal. HTH

Dennis

 

[MS50]

Thank you Dennis. Now I'm not sure my powder charge is optimal. This morning I stumbled upon Erik Cortina's thread on load development at 100yds. There's a high probability that I've been selecting the wrong group as my best node. I think I was lucky that using the round robin OCW method with my 223 and 308 loads provided good results at 300 and beyond. I know what a sticky is, but I have to figure out how to find them. I could've saved myself some time.

 

[mikecr]

What scope?

 

[MS50]

Sightron SIII 8-32x50. I haven't vertical or box tested it yet.

 

[Tim Singleton]

I would check seating depth at 300 yds
Sometime the 6br like the PPC shoot so well at 100 it's hard to see the best depth.
I do seating depth testing at 200. For that reason it's hard to know for sure when they are in a knot anyway

 

[Tim Singleton]

Try this seating depth method when you have a chance. There is a little noise in the middle of the thread but it doesn't get derailed to bad
This is the method used by most short range group shooters

http://forum.accurateshooter.com/threads/finding-the-right-seating-depth.3886764/

 

[MS50]

Thank you great stuff! This certainly opened a window for me. I'm going to try it on my 223 and 308 as well as the 6br. Should be interesting.

 

[Yote Hunter]

You need to do load work at longer range if that is your intentions. I also have found that what shoots well at 100 doesn't necessarily shoot well at longer ranges. A chronograph can help to show you a bad long range load even if it shoots impressive groups at 100 yards. You need to keep your velocity extreme spreads below 20 fps if you intend on shooting 1000 yards.

 

[MS50]

I tested the 87Vmax, 105 match burner, and 105 Amax today at 300 yards. Tested seating depths between .003-.015 off the lands. Shot .6in and .8in match burner and amax groups respectively at .009in off the lands. The Vmax .003 off the lands group was off the paper, and it didn't get much better. What a difference .004in made with the 105's. MV went up about 40fps in both 105 groups. ES in both groups was about 15. I'm going to bag the 87Vmax work for now. I assume seating in the lands is the key to success with that bullet. It is a secant ogive bullet, but the angle appears to be more severe than the angle on the 105Amax. Probably an illusion due to the length differences. Thanks for the feedback. Testing different seating depths has been an eye opener.

 

[Tim Singleton]

Seating depth is the key