New Rifle, need some info.

[barrysuperhawk]

Ok, with all of the fuss about putting 1x optics in Heavy Metal, it occured to me that I just bought a bushmaster ORC in .308, so maybe I could toss a dot on it and go with the flow. My problem is I have 5 days until CMMG [PB to 400+ yard shots] and that's precious little time to be messing with a new system.

So, what I have is a 16" .308 with a Votrex Strikefire 4MOA dot, and a few battlepacks of SA .308 ammo. My plan is to go tomorrow and zero this setup at 25 meters indoors. I don't have access to a chrono in this time frame, so I am going to have to guess at my velocity. A quick Google search turned up 16" velocities for SA between 2500 and 2600. The BC for the 147 is roughly .401 [again, per google]. All of this and a quick trip to Hornady's Ballistic calc gives me this data:

Ballistics Table in Yards 147 gr., .401 B.C. (25 yd. zero) www.hornady.com

Range (yards) Muzzle 50 100 200 300 400 500

Velocity (fps) 2500 2393 2289 2088 1898 1720 1555

Trajectory -1.5 1.1 2.3 -0.6 -11.5 -32 -64.4

Come Up in MOA -1.5 -2.2 -2.2 0.3 3.7 7.7 12.3

Range (yards) Muzzle 50 100 200 300 400 500

Velocity (fps) 2600 2491 2384 2179 1984 1800 1629

Trajectory -1.5 1.2 2.4 0.3 -9.3 -27.7 -56.8

Come Up in MOA -1.5 -2.2 -2.3 -0.1 2.9 6.6 10.8

Relative Dot 4 MOA 2" 4" 8" 12" 16" 20"

If I did the guessing right, and my assumptions are correct, out to 200, I ought to be able to put the dot on the target and go. At 300, I will need to stack the dot on top of a 10" plate, and at 400 since my dot subtends to 16" and my drop is around 30", holding one full dot width above an ipsc target ought to get me on target.

Am I on the right track? Did I miss anything or make any obvious errors? I normally [for the last 15 years] shoot a FAL, and this is quite a bit of change, 5 days befor a match.. Help?

[lmccrock]

Is the sight height 1.5"? I am thinking it is higher than that, more like 2.5-3.0". The Hornady calculator defaults to 1.5 but can be changed.

If the bullets are boat tail, then a BC of .4 is probably close, but a flat base bullet will be more like 0.34, so you may want to pull one, to be sure.

Lee

[Jesse Tischauser]

Dont change 5 days before a watch unless you are able to spend all 5 of those days getting to know that rifle.

[RiggerJJ]

IMHO, the 4moa dot is way toooooo big for precision shooting, espcially past 200 yds. Having said that, 75% of most matches rifle shots are under 200...

I shoot a 2 moa dot, when I shoot a dot, on my 308. My practice 22lr has a 4moa dot on it, and I am glad I don't use it (the 4moa dot) on my big boy rifle.

JJ

[Bryan 45]

Barry, I think if you change now you may very likely be in for a frustrating experience. Stay with something you know (FAL and irons) for this match. Spend some time with your new rifle between CMMG and your next match.

[barrysuperhawk]

Ok, yes, the SA uses BT bullets, and my sight height is closer to 2.5"

Here's new numbers:

Input Variables Firearm type Rifle Sight Height 2.5

Bullet Weight (grains) 147 Ballistic Coefficient .401

Muzzle Velocity (fps) 2550 Temperature 59

Barometric Pressure (hg) 29.53 Relative Humidity 78%

Zero Range (yards) 25 Wind Speed (mph) 0

Ballistics Table in Yards SA2 147 gr., .401 B.C. www.hornady.com

Range (yards) Muzzle 50 100 200 300 400 500

Velocity (fps) 2550 2442 2337 2134 1941 1760 1591

Trajectory -2.5 2.2 5.4 6.8 0.7 -14.8 -41.5

Relative Dot 4 MOA 2" 4" 8" 12" 16" 20"

Come Up in MOA -2.5 -4.1 -5.1 -3.3 -0.2 3.5 7.9

I am glad I asked, looks like I will be shooting point of aim to 300, *then* stacking at 400 and 2 dot heights at 500...

Barry, I think if you change now you may very likely be in for a frustrating experience. Stay with something you know (FAL and irons) for this match. Spend some time with your new rifle between CMMG and your next match.

I have been looking at moving to an AR10 platform since last year, and I have to start somewhere. Since CMMG last year, I have picked up 2 .308 AR's [a DPMS and the ORC] and a case of pmags in anticipation of the switch. I am familiar with the AR itself, it's going to be the optics that are going to take the adjustment. In point of fact, despite my familiarity, shooting the FAL has been frustrating too, hence my idea to switch.. If I go to a match that doesent allow optics in HM, I will probably still shoot the FAL, but the rules are evolving, and as much as it pains me, I need to evolve too. Doing it this way is just like learning to swim by parachuting into the ocean...

Edited May 14, 2011 by barrysuperhawk

[B_Ayers]

Actually - I would look @ the Horus talon. has mil reticle and is good out to about 800. if you have a 100yd zero on it there is not much different out to 400 between hte zero and the 2 mil line....fast on target transitions.

[barrysuperhawk]

Actually - I would look @ the Horus talon. has mil reticle and is good out to about 800. if you have a 100yd zero on it there is not much different out to 400 between hte zero and the 2 mil line....fast on target transitions.

Maybe for future matches, but I have 5 days, so no time to come up with anything new. Besides, the Horus talon is a 1-4x so I doubt they would let me just duct tape it on 1X and run...

[barrysuperhawk]

Ok, I am zeroed at 25, and I have my rangecard taped to my stock...here goes nothing.

[caspian guy]

Wow... brave man

I am always nervous about saying 25 yards and zero in the same breath. Any chance you can get to a longer range to at least check the windage?

Good luck and let us know how it works out.

[barrysuperhawk]

Oh, trust me Y'All will hear how it works out., I garoonn tee it.

I just have to memorize the mantra: " RO, I am intending on one shot per target, hit or miss. I will ENGAGE all targets.."