I'm installing a 10X IOR scope tomorrow on the AR-10t and the mil dots are set up for the 168 grain bullets, the barrel supposedly is optimized for the same bullet weight. Although a 1 in 10 twist would appear to me to be more appropriate for a heavier bullet.
However the rifle shoots the 175 grain MK bullet into delightfully small groups, much smaller then the 168 MKs. What sort of aggrevation will this rifle's non-standard appitite cause me?
Next question: Has anyone tried the Nosler 168 grain match bullet?
Jim

Mil dots are not caliber specific. There is 3.438 moa from large mark to the next large mark in the IOR MP8 reticle.

Your choice of the 175 gr MK is about optimum for the .308Win. Your 1:10 twist would stabilize a heavier bullet, even the SMK 190.

Velocity is one factor in the required twist for a given bullet length. The optimum twist for the 175 gr MK is around 1:11.25 at .308 velocity of 2600 fps or a little better. The 168s are best at no faster than 1:12.

Additionally, I suggest you try Varget with that 175 gr Match King. It is more temp insensitive, your accuracy load will almost surely be at higher velocity, and the velocity-pressure relationship is better than IMR4064.

If you require more info on mil dots or other reticles based on the milliradian such as IOR's MP8 and how to use for range estimation, wind hold-offs, and elevation hold-overs and -unders.

I've no experience with Varget, is it a stick or ball powder? Most anything would be easier to meter thru a powder measure then IMR 4064.
The MP8 reticle will be learning experience for me. I've been using an old Leopold 31/2 by 10 AO for 20 years. I learned the 'Kentucky' windage and elevation required for that scope whilst groundhog plinking, out to 400 yards.
I'll get a couple of pounds of the Varget and begin the load testing.
Thanks so much for you response.
Jim

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Jim, Hodgdon's Varget is a stick powder but much smaller than IMR4064. It meters very well through most measures. Still, it is best to drop the charge into your scale pan and verify every charge. I find that as the hopper gets below a third full that some drops are shy by a .1 gr or so.



With the SMK175 after initial sightin and zero at 100 yds you will come up 17 moa. Your stadia intersection will be on at 500 yds. The edge of the top bar or -5 mils is your 100 yd hold, 200 yds is -3 mil, 300 yds -2.5 mils, and 400 yds is -1.25 mil. Adding or dropping the required moa due to air density change from temp or humidity to maintain the 500 yd sight in will also maintain your hold unders for lesser ranges.



For wind holds in a 10 mph full value wind in comfortable to warm conditions hold .25 mil per hundred yd range to your tgt. 100 yd = .25 mil, 200 yds = .5 mil, 300 yds = .75 mil, etc. In very cold conditions use a third mil vice a quarter. The technique of holding under will put the holds closer to the horizontal stadia as range increases so that the mil marks are easier referenced when needed most.



To estimate range

tgt size in yds x 1000 / mils = range in yds

or

tgt size in inces x 27.8 / mils = range in yds





Hope this helps enough to get you started. Any other question do not hesitate to ask. Also many at www.longrangehunting.com can assist you with loading for the .308 and use of reticles based on the milliradian.



Rick

top to ensure ArkyPete has opportunity to see my last post

Got it.
I copied it off and have it in the case with the rifle, I'm thinking that I'll laminate it just preserve it.
I was headed out to the range this Sunday but the weather guessers are saying cool, windy and drizzle.
Thanks for your help and I'll keep you informed on my efforts.
Jim