First of all, you have made a great choice in a deer rifle. I've shot a 700 .270 for a lot of years and killed several truckloads of deer and hogs with it. I've tried all manner of bullet brands and weights and have settled on 130 grain Nosler ballistic tip bullets ahead of 55 grains of IMR 4350 powder. If you don't handload, the ballistic tips are available in commercial loadings as well. A great benefit to these are the fact that the polymer tipsdon't deform like lead tipped bullets. I am amazed that your 130s and 150s grouped so differently. Normally the 150s will only be an inch or two lower at two hundred yards.