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9/22/2017 12:11:25 AM
Posted: 9/8/2005 3:28:38 PM EDT
Deer season is almost here, and I am THIS CLOSE to finally springing for a 6.8mm SPC rifle. However, limited finances preclude me from buying new optics at the same time.
What can I expect using this scope with the 6.8 SPC?
Does the 6.8mm bullet flight parrallel the 5.56mm close enough to render the difference moot? Or is it going to drop like a rock, and I need to forget all about the range reticles? Would I be better off just using iron sights, or my ML2?
We hunt a relatively dense area where this should be a nice setup, and I absolutly thrill to the idea of dropping Bambi with an AR. Sporting purposes indeed!
Any experiences or recommendations would be appreciated.

I have been saving post 223 for far too long...
Link Posted: 9/8/2005 6:05:40 PM EDT
This has been discussed a gazillion times already, but...

With 6.8SPC, we're shooting a 0.32 - 0.37 BC bullet (depending on which load) at 2450 - 2650fps. For example, I am shooting the 110gr VMAX's at about 2640-2660 out of my 18". On the other hand, the factory Remington coming out right now is just under 2500fps with the 115gr SMKs. The hornady is right in the middle with the 110gr VMAX at 2550fps from a 16" bbl.

So if you have a BDC based on data for a 168 or 175gr 308 from a 20" barrel (or a 24" with weak loadings) it will be reasonably close for 6.8SPC. Also note that the 75-77gr loadings in 223 have a trajectory even more similar to 6.8SPC than 308-- a 0.32 - 0.39BC bullet at 2500-2670fps.

Of the ACOGs, the 308 suffix models will match 75-77gr 223 or 6.8SPC better than the 5.56-suffix models. But you can never trust the BDC without testing. Altitude, load, and gun differences will cause differences vs. the ideal trajectory as calculated for the BDC.

The 5.56-calibrated ACOGs are set up for M193 or M855, which are both WAY faster than 75-77gr 223, or 308.

For the 75gr black hills (or 6.8), I hold top-of-plate (10" plates) at 400 yards with the 400m line. Bottom inside of donut for 300, center/top inside for 200.

If you use that as a guide, you'll get "on paper" and can then develop the hold-overs for your rifle as exact as you want.
Link Posted: 9/8/2005 7:56:12 PM EDT
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