Can someone help me with bullet drop?

[Milkfisher]

Details....

AA bolt/20" barrel, hornady amax 123 factory ammo.

My questions.....

If I sight my rifle 2" high at 100yrds, what will it be at 200,300,400,500,600????

I can't seem to find ballistic info....

[LRRPF52]

Welcome. I use Berger's Ballistic program for quick reference.

If your muzzle velocity is 2500fps:

You need a 359 yard zero
100yds____+2.0 Mils
200yds____+1.5 Mils
300yds____+0.6 Mils
400yds____-0.4 Mils
500yds____-1.6 Mils
600yds____-3.0 Mils

You need to measure sight above bore height and your muzzle velocity. Hornady lists their 123gr AMAX load from a 24" barrel at 2620fps, and from a 16" barrel at 2350fps. I'm thinking you're around 2500fps with a 20" barrel.

[JASmith]

The 2" high at 100 is very close to a 200 yard zero. The 20" barrel will drop the muzzle velocity given by Hornady at http://www.hornady.com/store/6.5-Grendel-123-gr-A-MAX/ by about 70 ft/sec. You can calculate your own trajectory at http://www.jbmballistics.com using a MV of 2550 ft/sec or simply use a zero of 2.3" to get a 200 yard zero. Going with a 200 yard zero will give you a drop at 500 yards of 54.1" which is less than 2" more than the Hornady value for the 24" barrel. The 10 mph wind drift at 500 yards is 21.2" also.

If you are OK with -54.1" of drop and 21.1" of drift in 10 mph winds, you can take these to http://shootersnotes.com/calculator/...ight-pictures/ and see what the drop and drift are for intermediate ranges and what some different scope reticles will show for sight pictures at those ranges.

[Drifter]

Details....

AA bolt/20" barrel, hornady amax 123 factory ammo.

My questions.....

If I sight my rifle 2" high at 100yrds, what will it be at 200,300,400,500,600????

I can't seem to find ballistic info....

Actual results can vary slightly due to several factors (elevation / altitude, environment / weather, etc), but I will assume you're using an AR-15 platform (scope height ~2.7" above bore), a velocity of 2520 fps (10' from muzzle), and manually plug in a realistic BC of .490 for the 123gr A-max.

I use the Trajectory Calculator on the JBM Ballistics website. Here are the results for my local conditions:

100 yards- 2" high
200 yards- 0.5" high
209 yards- zero
300 yards- 8.4" low
400 yards- 25.8" low
500 yards- 53.2" low
600 yards- 92.3" low

[Milkfisher]

Sight above bore is 3".....Where does that come into play?

I'm confused now.. I've estimated velocity at 2515 FPS.

I need to know where the best zero would be to shoot effectively from 50 to 500 yards.

[JASmith]

The 2500 from LRRPF52, the 2520 from Drifter, and the 2550 from JASmith are all within the normal spread one might see.

I've looked at an awful lot of fancy zeroing schemes over the years, but have recently come to realize that it is truly hard to beat a 200 yard zero for most hunting purposes. Zero at that range, and you can see from Drifter's trajectory that you'll be in the vital zone for large game out to past 250 yards. If your actual velocity is in or close to this range, there won't be enough change in trajectory to worry about. Shoot enough, and you'll learn the slight corrections needed to center punch a coke bottle out to past 250 and do well on other targets to past 300.

Looking at the reticle-target image for much longer ranges tells one why a laser range finder will be needed. You may or may not want a turreted scope -- I would start with a simple mil-dot. Wind will trump everything...

Try the sight picture generator mentioned in the last paragraph in post #3 above and you'll get some interesting insights.

[LRRPF52]

I think asking for a zero that will keep you close from 0-500yds is stretching things a bit if you are planning on holding center of whatever your target is, unless the target is really large. Either you will have to dial elevation, or use a reticle for holds. Past 300yds, I prefer to dial my elevation. I usually dial anyway no matter what the range if there's time.

What are you shooting at, or planning on shooting? Is this for hunting, or ringing steel?

[JASmith]

Picking up on LRRPF52's remark, trying to reach too far with a center hold can become frustrating. If we take the canonical 10" diameter (or dinner plate-size) as the size of the vital zone, the bullet needs to stay within 5" of the line of sight between the muzzle and the maximum point blank range.

This means that somewhere a tad past the middle of the maximum point blank range the bullet is 5" above the line of sight. It drops back down to 5" below at the "maximum point blank range. That range is roughly 325 yards for the load you describe.

This is fine if all you're going to shoot is large game. The frustrating part of this pops up when you are plinking at small things like clay pigeons or shooting small varmints. You will need to hold 4 - 5 inches low between 100 yards and about 200 yards in order to impress your buddies. If you use the 200 yard zero, the correction will be less than 2" all the way out to past 225 yards -- good enough for clay pigeons, water bottles and squirrels.

Of course, if you use a turreted scope and dial in the range every single time, these things won't matter and we would not be having this discussion.

There is room for both schools of thought. My own view is that one is best served with a zero that accommodates casual shooting at the "minute of clay pigeon" level of precision over the middle ranges regardless of whether the longer range corrections are done with Tennessee Elevation or with clicks.

You will still need to correct for wind.

[Ullr]

lrrpF52,

I think asking for a zero that will keep you close from 0-500yds is stretching things a bit if you are planning on holding center of whatever your target is, unless the target is really large.

According to the trajectory charted in your first reply, it would be really easy. -3" @ 600 yds? Something is a bit goofy there.

[Variable]

Welcome. I use Berger's Ballistic program for quick reference.

If your muzzle velocity is 2500fps:

You need a 359 yard zero
100yds____+2.0"
200yds____+1.5"
300yds____+0.6"
400yds____-0.4"
500yds____-1.6"
600yds____-3.0"

I think there is an error in the data somewhere?

With iSnipe (and my local environmentals/geography) I get:

359 yard zero trajectory

Range. Path Elevation
100yds____+7.22" (-6.89moa)
200yds____+10.52" (-5.02moa)
300yds____+6.42" (-2.04moa)
400yds____-6.27" (+1.5moa)
500yds____-28.98" (+5.53moa)
600yds____-63.45" (+10.1moa)

[rasp65]

I ran it through 2 ballistic calculators that I have and my results were close to Variables.

[Milkfisher]

Thanks for the info Gentleman! I'm using my rifle in hunting applications. Coyotes hogs and deer. I think I'm goin to go with the 209 zero. Most shots will be sub 200, I just needed to know where I would be at 3,4,500!

Thanks a ton!

[Deezil]

Im not sure what LRRPF52's numbers are for either, definately not a grendel trajectory!

my ballistics are right around drivers also.

[JASmith]

I'm sure he will figure it out and let us know!

It was likely a simple entry typo like hitting a "4" instead of a "2" on the keypad when entering 2550 ft/sec. I tried that and got a similar trajectory..

I'm usually the one who executes a typo so I can relate to the discomfort.

[LRRPF52]

Sorry Gents, those were Mils, not inches. That trajectory would have qualified as lazer-gun, I think! I always generate my drop in Mils, because all my optics usually have Mil reticles.