Interesting results. Not surprised based on burn rates. Going to test the below loads tomorrow. Winner take all. Not testing N550 anymore, it is not temp stable. 35.8 gets 2947 but in summer heat can have significant velocity swings. 37.5 of N555 was 2890 with SD of 2.4 and .312" group. Loads are based on barrel times in QL.
N555 - 40.5 max
37.6 - 2897
39.3 - 3018
RL15.5 - 35.5 max
33.7 - 2937
I am thinking the N555 loads will be good back ups but RL15.5 looks like it might be big winner. I think @Niles Coyote might be on to something about the GT shooting tighter with faster burning powders. My Wife's GT is running RL15.5 and has shot more consistently over anything else I have tested to date. Both rifle builds are very similar. Both using OCD brass.
N555 - 40.5 max
37.6 - 2897
39.3 - 3018
RL15.5 - 35.5 max
33.7 - 2937
I am thinking the N555 loads will be good back ups but RL15.5 looks like it might be big winner. I think @Niles Coyote might be on to something about the GT shooting tighter with faster burning powders. My Wife's GT is running RL15.5 and has shot more consistently over anything else I have tested to date. Both rifle builds are very similar. Both using OCD brass.