New Barrel Break In 7MM Remington Magnum

[gilream]

I finally got to go to the range yesterday to break in my new 7 mm Remington Magnum barrel (stainless, Douglas 24 ½ inch). I spent 6 hours doing it. Was instructed by the ‘smith to shoot once and clean for 10 shots; then shoot a three shot group and if the copper did not clean up easily drop back to 1 shot groups until it became easy. I found that after 5 or 6 shots the copper was almost nonexistent. I ran the string of 10 shots and clean then shot three in succession beginning at 72 grains of H-1000. The three shot string cleaned up with almost no copper residue at all which was great. The final two shots cleaned up in a snap as well. The break-in was successful but I was hoping to find out what the max load was for a couple of powders using the Berger 140 gr. Hunting VLD with this break in process, but I got no pressure signs whatsoever. New Winchester brass, Federal GM215M primers, bullet seated .020 from contact point. I chrony’d the loads as follows:

RL22

65.6 2608

66.2 2940

66.9 2994

67.6 3051

68.3 ? (Forgot to move the chrony when I went to 100 yd target)

68.9 3193


H-1000

68.8 2920

69.6 2976

70.4 2997

71.2 3022

72.0 3031 clean

72.8 3085 fouled

73.6 3149 fouled

74.4 3150 clean

75.2 3177 fouled

With the H-1000 from 70.4 to 72 grains showed only a 31 fps increase in velocity. Can anything be read into this? Should I continue the strings until I get a cratered primer or a sticky bolt lift as originally planned? Or should I assume that I am near the max and begin load development now?
Mike

 

[4xforfun]

After I am finished with the 1 shot shoot and clean, I shoot 4 shot strings.....a fouler and a 3 shot group. I do not include the fouler in the group, nor does it figure into my chrono data.

I ALWAYS run my loads up to max...that way I know where "max" is on that paticular gun. If I try different weight bullets, I run each up to max. If I use different powders I run each of them up to max, also. I am sure I don't need to explain "max" to anyone!!! ;D

Looks like you have a good handle on things.

Have fun!!