The Accurate Reloading Forums THE ACCURATE RELOADING.COM FORUMS Rifles Long Range Shooting Figuring out drops question?Go | New | Find | Notify | Tools | Reply | |
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Here is my plan for tomorrow morning. I have a target I am shooting the same point on at 100, 200, 300, 400, 500, and 600. They say that it will give me the bullet speed, since I don't have a chronograph yet. As I can run the differences in drops between 100 and at every point through a ballistics program on Hornady or Lapua or whoever and mess with the speeds until I get what I have proven in inches below my 100 yard zero. How do I then set up my come ups on my scope turrets? I am guessing that the data needs to be proven at some point? By hanging another target at those know distances and proving it with my dials? For those of you more skilled in the sniper craft, am I on the right page? | ||
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Are you planning on shooting beyond 600? If not, you have the total bullet drop. Shoot your targets and let us know the drop; I will convert for you. Let me know if you have 1/4 inch or .1 mil adjustments. | |||
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Well. Here is what I think so far. Hornady 150 GMX with 82 grains of H1000 in a 28 inch 1 in 9.5 Proof Research barrel. The 400 yard target was 16 inches below point of aim. Using the consistant point of aim method of shooting at every distance 100, 200, 300, 400. I didn't shoot at 500 or farther because the range got busy. Online 4DOF tells me I have a speed around 3290 based on bullet drop at 400. Guessed using 4DOF Hornady mobile phone download I needed to come up 5MOA for 400 yards after I worked out my drop. I ended up about 3 inches below. So that will work. I have worked out that speed based on drop at 300 and 400 yards of 3 shots each using a benchrest. So my come ups on the MOA turret are: 100 0 MOA 200 0.6 MOA 300 2.1 MOA 350 3.0 MOA AND ETC. Or using the Reticle (it is MIL)this is a tran-sexual scope of MOA dials and a MIL reticle. 100 0 MIL 200 .2 MIL 300 .6 MIL etc | |||
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You only show your actual drop at 400; one MOA is four inches at 400, so your actual drop is 4 MOA - that is what my 28 Nosler drops at 400 but when zeroed at 200. Not sure how you plugged in a drop of 16 inches and then your ballistics software said the drop was 5 MOA? Something isn't adding up. | |||
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I am shooting on Thursday morning at the Fort Bliss Range. Should have it to myself, so I'll have a better idea of actual drop data. If I have time I will true data to 600 at 50 yard intervals. I have never shot there, so I don't know how much of a pain in the ass they are about backstops and targets if I am doing 50 yard intervals. You are right, my harry eyeball has: 400 for 4MOA 500 6.3 MOA 600 8.8 MOA I dialed 5 MOA to 400 and I was off a small bit 4 inches. I'll test that on Thursday. | |||
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Four inches at 400 is pretty huge - that is one MOA. What are your group sizes like at 400? Personally, I would zero at 200; the numbers you posted above look like a 200 yard zero, but you didn't tell us the cartridge. GO ADA. | |||
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300 Winchester with a 28 inch barrel. | |||
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I am already zeroed, if I have time on Thursday I'll adjust it to 200 or 300. I built a dope sheet based on my current dope today using the Hornady website. I also built one for a 300 yard zero. Pretty much + or -3.5 inches out to 375. | |||
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Zeroed at 100, I am not sure if I will have time Thursday or not. I'd like to shoot a bit more, but kind of holding my breath until I know how much time I have on Thursday. | |||
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Why a 150 grain bullet? I would go heavy in a 300 WM. Unless I am dead sure an animal is closer than 200, I range him. Once you range, bullet drop is a non-issue. But the wind will be... | |||
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I found out about this hunt late in the game, then found out late in the game they wanted me to use lead free bullets. So I had a ton of 150 Grain GMX bullets, and that is what I used. Was going to use a 195 Berger or 210 Accubond LR. Not really happy with the accuracy of the 150, but I can hit a pie plate at 600 with it. Elk hunt in October is going to be another story. I'll be shooting Accubonds. | |||
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I tried GMX in my .308 and wasn't too happy either. As for your zero, I wouldn't go to 300; if you bullet path goes as high as 3.75, you will have some that hit higher than that depending on your ability to hold steady and your rifle's accuracy. | |||
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It sounds like you are figuring it out. Does your calculated velocity agree with what the load data says you should get?
Here is something else to consider. I've used a variety of scopes that had questionable turrets. It seems they are typically not to be trusted because they are not repeatable, linear, etc. I even have an expensive vortex with a fancy long range turret, that sticks. This is worse when cold. I know to watch for it now, but it caught me a few times because you unscrew the elevation turret for a long range shot. I could sometimes dry fire the rifle and watch the reticle jump 20+ moa. Once it jumps, screwing it back in is fine because the internals are already against the turret screw. My point is, make sure your turret is doing what it's supposed to. If you can't trust it, then you should be able to at least use the reticle to hold for long range. | |||
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If you have a chronograph give this trajectory calculator a try. http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi It's very good and I've tried, was about dead on for me. You don't necessary have to shoot the distance targets as it will tell you how high you should be a closer targets like 100. I have an 8x57 I was wanting to shoot at 465 yards. This calculator told me how high I would have to be at 100 yards. I sighted in to that and it put dead on the target. Only thing I had to adjust for was the bullet drift. | |||
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What vzerone said. It seems to me like you're making it more difficult than it needs to be. You have an approximate velocity; plug that, a zero range, and the correct ballistic coefficient, which is in a lookup table on jam, and you will have what you want, and your shooting will confirm the minor changes from the calculations. Using jam with a known velocity and bc, I have been within ~1 MOA out to 600 yds with an AR and a 75 VLD bullet. Your experience should be similar. Clarence | |||
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