308 ballistics coefficient--custom dial from leupold

**Concealed9mm** · September 16th, 2014, 09:04 PM

Hey all,

Bought an ar10 and want leupold to make a custom dial for my ar scope. I am new to the 308 round, but I believe I want a 150g fmj to be used. I need to tell leupold weight, coefficient, muzzle velocity, etc. Can anyone give me any info on this? What is a typical or standard round for ar10

**BobGun** · September 16th, 2014, 09:14 PM

There is no general BC because every makers' bullet will have a different BC for a bullet of the same weight and caliber. You need to standardize on one bullet from one maker to be able to supply a BC.

**mosseater** · September 17th, 2014, 01:23 AM

You may be worried about something that is not the problem that it's made out to be. I know ballistic charts are what they are, and you're not going to cheat physics, but I have an M1A that came with a ranging scope calibrated for 168gr. match load (2500fps ish?). I took it to a range with a friend who is schooled on things "sniper" much more than me, and I was able to ring steel plates (10"x14"?) out to 700 yards with a variety of loads, most of which were M80 ball of various mfg, 146 gr-168gr, just by using the scope ranging brackets.

Granted, this is not groundhog accuracy, but almost. If you need to narrow it down closer than this, you'll need to sharpen your pencil, and your rifleman skills. I was lucky to have a still day and someone with knowledge, but I didn't miss even one plate all afternoon. YMMV. Congrats on the AR10. I'm officially jealous. Full range report required later!

BTW, guns with walnut shoot better. Jus sayin' ; )

**Concealed9mm** · September 17th, 2014, 07:21 AM

Thanks....I guess my question should have stated does it matter that much? Can I take a standard box to primarily shoot and if I shoot a different fmj would it affect it like crazy? Ideally in a few years I'll be hand loading and can get as precise as can be, but I just want to sling some rounds down range and punch holes in paper and be above average accurate

**BobGun** · September 17th, 2014, 10:11 AM

If you want to see how BC effects ballistics go to

http://www.jbmballistics.com/index.shtml

and check out some of the factory loads in this calculator. I would not worry about buying a custom dial unless you are shooting over 800 yards. I have DPMS .308 and I am using a Redfield Scope on it. It is setup for the 168gr FMJ at 2600 fps. I am shooting a 150 gr FMJ at 2750 fps and can keep all my shots on a 4" gong at 400 meters using the 400 yard setting on the scope. I reload and use a chronograph and spend a lot of time on my loads.

**aubie515** · September 17th, 2014, 11:31 AM

You can make your own dope cards without having to purchase a turrets and spend more money.

Get yourself a good optic...if you are on budget...I highly recommend SWFA SS12x with MIL/MIL with quad reticle.

Honestly, 150gr is a crappy bullet for 308...if you want the best BC, you are looking at 175/178gr either Sierra or Hornady Amax. I'm a fan of Hornady due to precision and cost.

If you are going to shoot heavier bullets >168gr...ideally, you would want a 1:10 twist barrel.

**JStem1283** · September 18th, 2014, 07:51 PM

I can tell you this, I worked up a load for my 308 bolt gun using Sierra MatchKing bullets 168gr HPBT which had a BC of I believe around .445. I used the same load but substituted to a Hornady A-Max 168gr BT which has a BC of .475. At 100 yards I was 4-4.5" low and almost 5" right...so depending on your rifle, yes it can make a big difference .