I have been shooting factory Remington 150 grain Sirrocco's for a while and have been very happy with the performance in my 7MM. But, I would like to know if anyone has ever loaded these for long range shooting and if so, what are your thoughts?
IME is "in my experience." G1 is another BC number. There are 2, a G1 and G7 and they are different. Look here at Berger's website. They have both BCs listed with their products:What is IME and G1? Not sure what exactly you are mentioning.
G1 vs. G7 Ballistic Coefficients — Which Is Right for You?
G1 and G7 refer both refer to aerodynamic drag models based on particular "standard projectile" shapes. The G1 shape looks like a flat-based bullet. The G7 shape is quite different, and better approximates the geometry of a modern long-range bullet. So, when choosing your drag model, G1 is preferrable for flat-based bullets, while G7 is ordinarily a "better fit" for longer, boat-tailed bullets.