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November 13, 2013, 09:38 AM | #1 |
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Simple bullet drop trajectory question
I'm trying to understand hold over and trajectory on my ballistic trajectory chart. At 100 yards my poi is 1.5" high with a 131 yard zero distance. And the bullet drop is -8.3" with a -3.9 MOA (-4.15") at 200 yards. I assume if I:
- held 4.15" high at 100 yards, it would hit the bull at 200 yards, or - I could hold 8.3" high on the 200 yard bull and hit it (which would be 5.65" high at 100 yards). Thanks.
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What direction did that last shot at Kennedy come from? Last edited by tpcollins; November 13, 2013 at 09:53 AM. |
November 13, 2013, 10:10 AM | #2 | ||
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I'm not sure I understand the question.
Quote:
Quote:
If I understand the question correctly. |
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November 13, 2013, 10:25 AM | #3 |
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I can't paste the entire chart but at the 200 yard line is the following data:
Range …. Drop ... Drop yd ………... in …... MOA 200 …... -8.3" ….. 3.9 It's my understanding that the "Drop MOA" would be the same as "Clicks Up" on the vertical turret to hit the bull at 200 yards. And on it's way to the 200 yard target it would be roughly 5.65" high as it passed thru the 100 yard plane.
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What direction did that last shot at Kennedy come from? Last edited by tpcollins; November 13, 2013 at 11:42 AM. |
November 13, 2013, 11:15 AM | #4 |
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Technically, you'd be holding 4.15" high at 100 to hit the 200 yard target dead on... but why would you do that? If you want to hit the 200 yard target, you should be aiming at the 200 yard target and holding 8.3" high.
You're confusing the path of the bullet with the path of the beam of light you're using to aim. The light is going straight, only the bullet is following a curved path. Hold over is linear. 1" at 100 is 2" at 200 is 3" at 300 is 4" at 400... is 10" at 1000. All you care about is how low the bullet is at the distance you want to hit. If it's 8" low, you aim 8" high.
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November 13, 2013, 11:57 AM | #5 |
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[QUOTE]Technically, you'd be holding 4.15" high at 100 to hit the 200 yard target dead on... but why would you do that? If you want to hit the 200 yard target, you should be aiming at the 200 yard target and holding 8.3" high./QUOTE]
Thanks Brian, that's what I'm looking for. The reason I asked the question that way is I have a 3-9x36 Swarovski with the 4A reticle. The sub-tenstion from the crosshair center to the top of the post is 8.3" at 100 yards - half of that is 4.15". So I think if I center the target between the crosshair and the top of the post at 9x, it should smack the 200 yard target dead nuts. If I frame the target the same way but at 100 yards, it should hit that target 5.65" high but go beyond and hit the 200 yard target dead on - or at least that's my thinking . . .
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What direction did that last shot at Kennedy come from? |
November 13, 2013, 12:46 PM | #6 |
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This must be a slug gun or a muzzleloader. What bc and mv are you using for your calculations?
Do you want to sight it in for deer hunting? |
November 13, 2013, 12:59 PM | #7 | |
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If you're literally referring to the SAME BULLET hitting a 100 yard target and then carrying through to a 200 yard target, it's unlikely even with paper.
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November 13, 2013, 01:33 PM | #8 |
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Thanks Brian.
[QUOTE]This must be a slug gun or a muzzleloader. What bc and mv are you using for your calculations? Do you want to sight it in for deer hunting?/QUOTE] Yes, I was hoping this forum could answer this for me. .451" dia Barnes .50 cal 250 gr TMZ, BC - .210, 2000 fps, 1.4" scope height, impact is 1.5" high at 100 yards, with a 132 yard zero yardage. - at 200 yards, drop is 8.3" with 3.9 MOA drop (16 clicks up) - at 255 yards, drop is 21.1" with a 7.9 MOA drop (32 clicks up) I converted the inches to MOA so it would match the JBM chart. I'd like to be able to turn the scope up to 9x and shoot a maximum of 200 yards. To me, the data indicates if I "frame" a deer's back and belly at 200 yards with the crosshair and post, I should hit it in the middle - yeah or nay?
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What direction did that last shot at Kennedy come from? |
November 13, 2013, 02:08 PM | #9 |
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Yeah.
Sight in dead on at 100, or maybe .5" high. That will put you within 2" out to 130 yards or so. Using the top of the post as an aiming point, you'd be 8 or 8.5" high at 100, you'd be about 5" high at 60 yards, 9" high at 125, and 5" high at 200. A hold with the top of the post at the bottom of the deer's chest would put the bullet between 5" and 9" up from the bottom the the deer's chest at any range from 60 to 200 yards. |
November 13, 2013, 02:22 PM | #10 |
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Thanks SSA, but if I had wanted it sighted in at 100 or +.5" high at 100, I would have done that in the beginning. Thanks anyway.
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What direction did that last shot at Kennedy come from? |
November 13, 2013, 02:27 PM | #11 |
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At least for hunting purposes, I don't know anybody who zeros at 100. Typically, 0.75-1.5" high is normal, depending on cartridge and vital zone size.
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November 13, 2013, 04:05 PM | #12 |
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Let me ask it this way. If I'm zeroed 1.5" high at 100 yards, and I aim 3.9 MOA high at 100 yards, that's roughly 4.15". I'm under the impression that this same 3.9 MOA at 100 yards would become 8.3" at 200 yards, correct? I think it should hit the bullseye at 200 yards then.
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What direction did that last shot at Kennedy come from? Last edited by tpcollins; November 13, 2013 at 05:54 PM. |
November 13, 2013, 04:25 PM | #13 |
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Well, it gets a lot less complicated if you pick a term and stick with it. They're the same at 100 (basically), an inch is an MOA. 1 MOA at 100 is 1.047". Most people just drop the .047 and call them the same. That's fine at 100 but that 0.047 adds up as you get farther out. It's best to just pick a term and use it. Either inches or MOA, don't mix them.
Remember, the light beam is going straight. It doubles in height when distance doubles. MOA also doubles with doubled distance. If you're aiming 3.9 MOA high at 100, you're also aiming 3.9 MOA high at 200 but the actual amount in inches doubles. Don't mix them up. Think in MOA or think in inches. Don't try to do both.
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November 13, 2013, 06:00 PM | #14 |
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[QUOTE] MOA also doubles with doubled distance. If you're aiming 3.9 MOA high at 100, you're also aiming 3.9 MOA high at 200 but the actual amount in inches doubles.[/QUOTE
Thanks Brian, that's exactly how I was understanding it. The only reason I was using inches and MOA is the scope's sub-tensions are in inches, the JBM chart is in MOA. So as long as I use 1.047" for one MOA, I figure I can multi-task rather easily . . . thanks again.
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What direction did that last shot at Kennedy come from? |
November 13, 2013, 08:11 PM | #15 | |
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Quote:
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November 13, 2013, 08:41 PM | #16 | ||
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Quote:
I use JBM all the time, they list inches and MOA. Quote:
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November 13, 2013, 10:06 PM | #17 | |
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The math involved in bullet flight is complex enough, especially when considering all of the different variables involved, I like having at least one standard. All of my hunting and target centerfire rifles are zeroed at 100; with the load currently shot the most often. (I only change them if I have a specific/really good reason to do so.) I hand load, and check my loads with chronograph, BC info, charts, and then test them out in the field to bear out if they are doing "what they are supposed to do"; amazing what different temperatures can do to a load. So, I do change my scope, but mainly for temperature differences or changing to a different "mostly used" load to bring it back to 100 yard; think temp difference between summer and Winter in Alaska, it is noticeable. When I start "reaching out" I sometimes use those knobby things on the sides of the tube-thingy. But, mostly I know the bullet drop from 100 yards and compensate for it, either with the reticle or with turret adjustments. The bullet is going to follow the same path, gravity being fairly constant, regardless of how one wants to view it, what matters is if the shooter understands the relationship of how he/she is viewing it to the actual flight path. YMMV
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November 14, 2013, 07:21 AM | #18 |
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I used to sight in 3" high @100 yards with everything but have shifted to around 2" with most rounds. A 2" high @100 yards will give you slightly longer point blank(hold on brown) range w/o causing you to shoot excessively high at shorter ranges. If you need a 5" high @ 100 yard sight in, you really need a longer range capable cartridge.
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November 14, 2013, 09:25 AM | #19 |
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Simple bullet drop trajectory question
Some places you can only hunt with shotgun or muzzleloader. There aren't choices for "longer range capable cartridge".
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November 14, 2013, 02:54 PM | #20 | |
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In the USA, long ago, rifle targets were established that had scoring rings even inches apart. And were shot at 100 yard increments or simple fractions thereof. So both scope and metallic sights had their adjustments such that one full unit moved impact exactly 1 inch for every hundred yards of range. And virtually all targets have scoring rings and adjustment grids on even inch spacings. Telescopic sights with external adjustments moved .0005" per click on their 40 tpi knobs. With the 7.2" standard spacing of the two rings on bases, four clicks moved impact 1/3600th of the range. That's exactly 1 inch per hundred yards. Iron sights had a 30" standard sight radius and their adjustment screws were also 40 tpi. One third turn of a knob moved the sight .008333" and that's exactly 1/3600th of 30 inches. They had 3 MOA per turn; exactly 1 MOA per third. But someone learned in the late 1960's that their brand new scientific hand held calculator had trigonometry functions and they thought the rifle shooters were too out of date. But these folks didn't have any problems with the different number of yards in the different distances called "one mile" whether it was statute, nautical, radar, Scandinavian or metric miles. I perfer the shooter's MOA over the trig one; much simpler and mentally manageable. |
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November 15, 2013, 06:51 AM | #21 |
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"Some places you can only hunt with shotgun or muzzleloader. There aren't choices for "longer range capable cartridge".
In that case, you shouldn't be trying to shoot at those distances. |
November 15, 2013, 08:52 AM | #22 |
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Simple bullet drop trajectory question
He's only asking about 200 yards. There are plenty of muzzleloaders and some shotguns that can reach 200 effectively. It's really up to him to decide his effective range.
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November 15, 2013, 10:06 PM | #23 |
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Calculations can be fun. Careful when you mix angular and linear units. For shooting at living things the mathematical alchemy is just to get you to an initial sight setting for the distances in question. You get the real answers by burning cordite.
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November 16, 2013, 11:03 PM | #24 |
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I sight rifles at the indicated POI for point blank range for the load and rifle I am using, for big game. My 25-06 is 2.5 inches high at 100 and 3 inches low at 320 yards (3 inch vital radius). That way I don't get to guessing on hold over etc. If it looks long--and my judgment can be poor on distance to mulies and speed goats-- then the point of aim is "a couple of inches below the highest hair on their top line." If they ain't aware of me and I can fumble around and get the range finder out and use it, then a better estimation of hold over is possible.
A guy I know shoots bench rest and long range shooting, and he zeros at 100. He is more into the technical aspect of figuring trajectory than me. |
November 17, 2013, 12:55 PM | #25 |
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[QUOTE]He's only asking about 200 yards. There are plenty of muzzleloaders and some shotguns that can reach 200 effectively. It's really up to him to decide his effective range./QUOTE]
Brian is exactly right. I think 200 yards is the max for both me and my muzzleloader to be able to dispatch a deer as humanely possible. The last thing I want to do is make a poor hit and have it go off and die unrecovered.
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What direction did that last shot at Kennedy come from? |
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