I am looking to by a Leupold Mark 4 2.5-8x36 M2. I like the ½ moa adjustment and was wonder what would be the maximum distance you could shoot with and 8 power scope in 6.5 284 Norma? Do long range shooters us a 8X? Thanks for you help.
You'll probably get a wide variety of opinions on what power is sufficient. It's really a personal thing. Some will say 10x works good for them out to 1000 yards, others prefer something in the 3-15x, and quite a few like the 5.5-22x route. Personally I prefer 12-42x as the eyes aren't what they used to be but mirage can be a factor. I think generally most would agree on 1/4 moa is preferred over 1/2moa. As far as maximum distance it's hard to say as I'm not familiar with your rifles accuracy, your skills etc. If it were me I wouldn't be pushing it much past 500 yards but, as I said my eyes aren't what they used to be. Hopefully others will join in here and lend their comments as well.
There are people that shoot 1000 yards with iron sights. Most top class shooters seem to use something like 100 yards times magnification for long range shooting. Me personally I can only do 50 yards times magnification and still get a decent sight picture.
As for MOA clicks, for hunting the 1/2 should be plenty, the 1/4 click gives you 1 " more adjustability at 400 yards.
The actual magnification of the Mark 4 2.5 x 8 x 36 M2 is 3 x 8.7. If you compare that to the Mark 4 3.5 x 10 which has an actual magnification of 3.2 x 9.5 there is not that much difference. The biggest differences are the lack of side focus on the 2.5 x 8 and it weighs 3.5 oz. less.