100yd zero set...drop at 200? 300? getting ready for deer season

[hydrotech]

Hey guys, I have been in a hurry to get some data together for my grendel now that I have it back together. I have deer season in KY this weekend! yesterday before work, I zeroed it at 100 yards. This morning before work, I tried to get it squared away for 200 and 300 but I didn't have time to replicate and shoot many rounds. Probably won't before I leave friday for Deer camp. Based on the 15 rounds I shot today It looks like with a 100 yard zero i need to come up 10 clicks to zero at 200, and come up 25 or 26 clicks from 100 zero to be on target at 300 yards. 123 sst on 28.3 g 8208, 18" barrel, vortex viper 4.5x12 1/4 clicks.
Does that sound about right?

[davidj]

http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi

[Slappy]

Hornady has a ballistics calculator also on the website, just punch in the info and it will get you very close. BANG BANG!!

[LRRPF52]

What's your scope height?

Muzzle velocity? Should be ~2500fps

Here is what I generated assuming a 2.7" scope height, 2500fps, 59F, sea level barometric pressure 29.92" mercury.

       Range    Velocity    Energy     Trajectory         TOF          Drift
      (yards)     (fps)     (ft-lb)        (MOA)         (sec)          (MOA)
          0      2500        1707           0.00         0.0000         0.00
         50      2414        1592          -1.15         0.0611        -0.36
        [B]100      2330        1483          -0.00         0.1243        -0.73[/B]
        150      2248        1380          -0.63         0.1898        -1.11
        [B]200      2167        1283          -1.77         0.2578        -1.50[/B]
        250      2088        1191          -3.16         0.3283        -1.91
        [B]300      2011        1104          -4.72         0.4015        -2.33[/B]
        350      1935        1023          -6.43         0.4775        -2.77
        400      1861         946          -8.26         0.5566        -3.22
        450      1789         874         -10.21         0.6388        -3.70
        500      1719         807         -12.30         0.7243        -4.18

Since you have 1/4 MOA clicks, and you are 1.77 MOA low at 200yds with a solid 100yd zero, you would need 1.75 MOA to come up to a 200yd zero.

1.75 MOA in .25 MOA clicks = 7 clicks up.

If your scope is lower, then you will need more clicks up. For example, a 2.2" scope height will put you at 2 MOA low for 200yds.

Measure your scope height from the center of the bore to the center of the tube. If you have normal rings, you can use the space between the rings, or the center of the windage knob for your center of scope tube landmark.

[hydrotech]

Ill measure my scope when i get home. the thing I don't like about the JBM ballistic calculator link is i don't have a chrono so I can't input velocity. Do they make a ballistics calculator where you put in your 100 yd zero and how many inches your bullet drops at 200 and 300 and it calculates your velocity and how many clicks up at extrapolated distances?

[bigbear_98]

So I understand your question to say 2.5 moa (10 clicks divided by 4 clicks per moa) at 200 and 6.5 moa (26 clicks divided by 4 clicks per moa) at 300?

If this is what you found on paper and using my data, that means your muzzle velocity is only 2261fps.

I'm shooting a 20" barrel but factory SST is 2528 10' off my muzzle.
My come ups are 1.75 moa (7 clicks) at 200 and 4.75moa (19 clicks) at 300.

It might be easier for you if you thought in MOA instead of clicks.... It is for me.

ETA: HAH! I'm too slow...

[hydrotech]

I have an old school phone and no ballistics calculator and no internet at my house deep in the country, I have gotten in the habit of just taking my databook out to my bench behind the barn. I sight in a rifle at 100, then shoot it at 200 yards and write down how many inches it dropped then roughly go by .25 click = 1/2" at 200 and turn up that many clicks and try and see if its on target. then actually write down the number of clicks up from 100 I had to go to 200 and be on target. Then i move out to 300 yards and count how many inches my bullet dropped. then go by .25 click = 3/4" at 300 yards and go up that number of clicks. I write down how many clicks it actually took up from my 100 yard zero to be on target at 300. I can only use the net at my job in town. Am i going about things the wrong way?

[LRRPF52]

That is old school, but the bullet doesn't lie. What I have seen with these ballistics programs is that if you have accurate data for all the variables, they can be frighteningly accurate. For the distances you are shooting, your margin for error is much lower, as long as you keep in mind your 10" vital zone.

A 200yd zero will give a nice, no elevation hold necessary zero for your common hunting distances. With a 200yd zero and a 2.5" scope height, you will be 2" high at 100yds, assuming a 2500fps mv.

[dmsims21]

Ill measure my scope when i get home. the thing I don't like about the JBM ballistic calculator link is i don't have a chrono so I can't input velocity. Do they make a ballistics calculator where you put in your 100 yd zero and how many inches your bullet drops at 200 and 300 and it calculates your velocity and how many clicks up at extrapolated distances?

I have the Nikon Spot On app. It has a feature that will estimate velocity based on drop from 100 to 200. It works pretty well. I have a BDC reticle, so the app will tell me what distance corresponds to each mark on the reticle. . I tape the chart to my stock. That way I don't have to mess with dialing in elevation while hunting.

[LRRPF52]

Another technique you can use is to paste your reticle drop chart inside your flip cap, if you use flip caps on your scope.



You can also draw your reticle and indicate the drop points on it:

[JASmith]

Take look at zeroing your rifle 1.5" high at 100 yards next time you go to the range. That zero will let you hold more or less where you want the bullet out to past 225 yards. Beyond that range you should have time to think about accurate range estimation, holdover, Kentucky wind age, clicks and fussing.

There' a bit more discussion in this paper Revisiting Maximum Point Bank Range".

[hydrotech]

hornday ballistic.jpgOk I used the hornday ballistics calculator. Playing around I got some drop data that matches up with my actual results from 100, 200, 300 yards. I had extrapolate to 600. I also converted drop in inches to # of clicks up I need to zero...f i did my calculations right. any of you want to verify my calculations? Think the extrapolation will hold close out to 600 if my 100-300 data matches up?

[LRRPF52]

2400fps seems slow to me for an 18" with factory ammo. My 16" gets 2450fps average with Hornady 123gr, as well as Precision Firearms 123gr Scenar.

Can you not zero at 200yds on the morning of?

[hydrotech]

It may seem slow but that's pretty close to what I measured for drop on actual targets I shot with a tape measure. If i don't go bowhunting today, I may shoot my rifle this afternoon. maybe Ill try the 200 yard zero. I'm heading out tomorrow after work. I'm confident I'm good out to 200 yards right now and I wont shoot a deer out past that with my grendel. If I hunt where I have a longer shot I'll have my 7-08 boltgun. the 700 acre family homeplace I hunt has a big mile long ridgetop cleared for haymaking and the rest is lower wooded hills and hollers on both sides of the cleared ridgetop. That long ridgetop would be perfect for someone with a 338 lapua or .50 cal with a big nightforce that wanted extra long shot practice out from 1/2 a mile to 1mile from the observation deck on the cabin.

[LRRPF52]

Still need to know your scope height from bore center.