Load development question

[flyinbrian]

I built a .243 Winchester rifle intended for long range target shooting on a Stevens 200 short action with an 8 twist 28" Lothar Walther barrel. I've read about OCW but during load development I haven't really been able to tell a major difference in accuracy from load to load. Is this common? Could someone look at these targets and advise me on the correct load? I settled on the 48.4 Retumbo load, but am open to advice. Thanks in advance. These targets were shot at 100 yards.

 

[model 12 toby]

I'd go with the 47.6. Maybe have a shoot out with the two at a longer range????

 

[22BRGUY]

I agree with 47.6...might try 47.4 and 47.8 to see if they stay in as nice a line as 47.6 for vertical dispersion.

 

[Chuckhunter]

I just went through this and with Erik Cortina's help I found a pretty good node. I'm now refining with seating depth adjustments. After looking at your targets, the last three are all shooting to basically the same point of impact with very little vertical. I would choose 48Gr's which is right in the middle of the node and play with seating depth. Perhaps you could ask Erik if he agrees with this observation. Check out his thread on long range load development at 100yds. It's further down the page in this section.

 

[fredhorace77]

http://forum.accurateshooter.com/index.php?topic=3814361.0

http://forum.accurateshooter.com/index.php?topic=3818095.0

 

[trailrider121]

I like 48grs too,looks to be center of node. Thanks for sharing.

 

[Erik Cortina]

I agree with 48.0 since we don't know what I would do above 48.4 gr.

Load 48.0 and adjust seating depth and you will get there as it's obvious your rifle shoots.

 

[flyinbrian]

Thanks for the feedback, guys. I've been cogitating on Erik's thread on long range load development at 100 yards, and it's a font of great information, but I have one question: If I understand correctly, seating depth is started at a jump of .020" and then moved toward the lands in .003" increments?

Thanks in advance.

 

[Erik Cortina]

Thanks for the feedback, guys. I've been cogitating on Erik's thread on long range load development at 100 yards, and it's a font of great information, but I have one question: If I understand correctly, seating depth is started at a jump of .020" and then moved toward the lands in .003" increments?

Thanks in advance.

No, it's started at Jam -.020", and then for seating depth testing, start at Jam -.010" and work away from lands in .003" increments.

 

[flyinbrian]

Gotcha, thanks Erik!

 

[BoydAllen]

I tend to discount the OCW method, because it does not seem to recognize the importance of seating depth. I tend to start testing seating in the lands some amount, depending on the ogive shape, and my previous experience with that shape, and then work on powder charge, and then refine depth.

Also, under what conditions were the groups shot? Flags? Bench quality? Rest/bag setup? Trigger pull? Shooing style? Test groups are only as good as the control of the other variables.

Also, IMO one should do a separate powder workup (smaller in range) when going from in the lands to out, or vice versa, because of the differences in pressure with a given amount of powder. Even when I am making a slight change in the lands, that I know will change pressure slightly, I may alter the charge to compensate.

 

[model 12 toby]

I just love when two of em make the same hole. 3 of em makes me have two good days. Alters my mood.