I just put a 2.5-8 on my ‘new to me’ 308, and at 8x I shot groups equal to and better than the groups I shot with the 4-20 I had on the heavyweight 5R .308. The new rifle was harder to shoot as its 3.5 lbs lighter, and the 5lb trigger wasn’t helping, but when my technique was good I could have shot deer just as far out as the 5R.
However, I’m acknowledging that I don’t need or want to shoot that far anyway, but it gives you a measure of confidence that the system (the rifle plus shooter) can make it count within the distance I have determined is ok. For me that is the point where the bullet still retains 1500ftlbs energy. Yes, I know that the experts say 1000ftlbs is the minimum, but I want to make sure I can retrieve that deer in the scrubby areas I hunt. With the .308 that works out to be around 300yds, and that’s more than enough for this guy.
In terms of scope magnification, I have heard that you need 1x for every 100yds when shooting at deer size targets. My observation is that this is correct for a reasonably well practiced rifleman. Be conservative and make it 2x per 100yds and I think you can’t go wrong
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