How much of a difference will using different types of brass, make on my accuracy out to lets say 600-700 yards gun)? 7mm brass has become more and more difficult to find. I've been shooting Remington brass with excellent results, but can't find any more to save my life. I came across some Federal Premium brass the other day and ordered it just because it's the only new brass I've been able to come across. My primary purpose with my rifle is just to familiarize me with long range shooting (I'm a newby ), and is used for mule deer and elk. Thanks guys.