Data Discrepancy 7PRC

[Powerstroke]

CO archery season is about done this year and time to move on. I didn't have much time to work on loads last fall for the 7PRC and now that I have time, I'm seeing some concerning max load variances. Has this been typical since the inception of this round? I was provided quick load data last fall for 175gr EH and decided to use N570. That data provided shows a max load of 75.1 grains. From that data I started working up with the time I had and settled on 74.5gr which gave me (I'll call it half inch) groups.
Last night I was on Viht's page and looking at new data. The max load shows to be 69.8 grains for the N570/same bullet. I've seen variances in data in the past, but this one seems excessive? Thanks for any input......

 

[SJB358]

I think a guy would drive himself crazy without a chronograph. Look at the variance with a 270 Win and 130 and H4831 for instance. Some max at 58 while some max out at 62. I think it’s literally a guide and you know what’s safe in your batch of components and rifle.

Good to see you around. Been awhile!

 

[RL338]

How does your velocity compare to their published data? Some brass manufactured today does hide pressure very well.