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Discussion Starter · #1 ·
Let me start off by saying that I am no ballistics expert. In fact, I don't even reload (yet).

Several years ago, I took a doe at a considerable distance, shooting a 150 gr .30-06 (Winchester supreme, powerpoint plus). My friend was in the tripod with me, and we both marveled at the shot placement/distance when we saw the doe collapse, and after walking over to get it. For the past couple years, we have debated how far the shot was (he swore it was 400+ yds, while I thought it was more like 350yds). The terrain was not conducive to pacing it off, and we were separated by a pond. Anyway, I was down there this past weekend, and this time had a range finder. The verdict was 386 yds.

Now I got to thinking: From all the ballistic charts you see, they say that a 150gr .30-06 will drop roughly 24" at that range. My rifle is sighted in 1" high at 100yds. When I shot the doe, I placed the crosshairs just below her spine (about 5" high), and the shot hit directly behind the shoulder. By my calculations, this means that the bullet dropped about 6".

My question is, how can this be? If you go by the ballistic charts, I would have had to aim almost 2' high in order to hit her behind the shoulder. I realize I am over-simplifying this, as there are variations due to thermal conditions, elevation, etc. But certainly they could not account for such a large discrepancy.

Can anybody help make sense of this?
 

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Might the terrain have something to do with it? I mean is it perfectly level? I'm by no means an expert, but I imagine they test ballistic trajectory on as level a testing ground as they can find. Wind might also be a factor. I don't know. Interesting.

Theo
 

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Discussion Starter · #3 ·
I'm not sure about wind being a factor, as that would affect the horizontal shot placement more than the vertical (drop). That day, winds were below 5mph, it was about 40 degrees, and RH about 35%.

As for the terrain, I was on the top of a "hill". I use quotations because I was about 22 miles west of Selma, AL. There isn't a whole lot of topograhical variation in the black belt region of the state. Bottom line, there was less than ~20' difference in elevation between the muzzle and the deer.
 

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Ballistic charts are not considered to be absolute.

They will give you a ball park trajectory indication. Unless the ballistic tests were done with YOUR ammo and YOUR firearm, there will be variables. Barrel length, ambient temperature, ammo - including ballistic co-efficient of the the specific bullet, etc. all have an effect on bullet drop. Also, what range did the ballistic chart indicate that the test firearm was sighted in at? If it was zeroed at 100 yds. and your rifle is +1" at 100 yds. it can have a much greater effect with regard to bullet rise/drop at 200, 300 and 400 yds.
 

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Discussion Starter · #5 ·
Most of the charts I see give data at 200, 300, 400, and 500 yds. So I'm not sure where the were zeroed at. You make a good point. But as I said, I don't see how those differences could make for such a huge difference. I mean, we're talking about a foot and a half.

Around here, you very rarely get a shot that far, unless you are hunting on a power line or a clearcut. I'd say the average shot is below 100 yds. That's why I have always thought it useless to engage in the classic .270/.30-06 trajectory debate. Until I had this experience, I kind of assumed that a .30-06 was far less suited for longer ranges. But now, I'll put a 150 gr '06 up against a .270 any day.
 

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Forstr said:
Most of the charts I see give data at 200, 300, 400, and 500 yds. So I'm not sure where the were zeroed at. You make a good point. But as I said, I don't see how those differences could make for such a huge difference. I mean, we're talking about a foot and a half.

Most of the good charts will tell you what zero they use, as well as ammo and barrel length.

The difference between a 100 yd zero and a 150 yd zero, plus the difference between a 150 gr. and 180 gr. bullet, plus the difference between a 16" barrel and a 20" barrel - can easily account for a foot or two of variance at 400 yds.
 

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As temp goes up, the bullet will rise (1/2 - 1 MoA for 20F increase) due to air becoming less dense. That might account for up to say 4".

Winchester's BC of .258 seems pretty darned low for a spitzer looking bullet. I'd figure it should be upwards of .3--that might make another 2" difference.

The angle (change in elevation) doesn't matter until you hit 20degrees (and then, regardless of up or down, the bullet will always hit higher).

Altitude can play in as well, but not unless we're talking about something like 5000ft difference from where you sighted in at.

In general, I'd say that yeah, those numbers don't add up well. I can only ask if you're sure about that 1" high at 100yds (and not 2 or 3") and finally: it's better to be lucky than good.

Ty
 

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Discussion Starter · #9 ·
I guess it's really not possible to be able to say for sure, with all the variables. My rifle is consistantly 1" high at 100yds, I'm sure of that. I guess it really doesn't matter, so long as it is accurate. I'm not complaining, by any means: just curious because it seems so far off from what I would expect.
 

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In a nutshell, what I am saying is the difference of 1" at 100 yds. can easily mean a difference of 1 foot (or more) at 300 yds. Add all the other variables into play (not just the zero range) and it is not unreasonable to assume a 1 - 2 foot difference in POI at 300+ yds.
 

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Yup, if you are an inch high at 100, you will be on at 165 and 24" low at 385, or thereabouts, depending on actual bullet BC and velocity.

I don't know an easy way to break it to you;
you missed.
That is, you pulled the shot high, relative to your trajectory and aim point, and was lucky enough to hit the deer anyhow.
 

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Jim Watson said:
Yup, if you are an inch high at 100, you will be on at 165 and 24" low at 385, or thereabouts, depending on actual bullet BC and velocity.
Is .30-06 really that loopy? I would have thought it would be flatter than that. Say the second crossover out past 200 yards or so.

Regardless at 386 yards I do agree he "missed" technically.

PS Still a nice shot. Furthest living thing I have shot was a prairie dog at around 100-150 yards (just a guess since it hit a tad high).
 

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For that cartridge, I'd be tempted to sight it 2" high at 100yds. That would put you right on at 200 and 8" low at 300yds.
 

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That's very close to 400 yards - and a very long shot.

While you say you sighted just below the spine - at that distance, and depending on how much your scope reticle subtends - you may have actually been aiming considerably higher. Your scope may be sighted higher than you think, or you may have pulled the shot high at trigger let off.

There are some things that will throw a shot high - like resting the stock forearm on a hard object or surface, unstable shooting stance etc. I am speculating of course, but there may have been some element of "luck" involved in your hit.

Have you rechecked your rifle zero with the same load at say 100 or 200 yards since?
 

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Discussion Starter · #15 ·
Yeah, every year when I brake it out I make sure it's still where it should be, and didn't get knocked off the year before. I start out with a good rest on a bench and shoot at 100yds. It has stayed 1"high at 100 since I sighted it in. I guess it could have been luck, or a combination of other things. What I need to do is find a place where I can target shoot at that range, and maybe I can see if I can achieve that kind of accuracy again. I guess that's the only way to really tell.
 

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a tri-pod 10 or 15 feet in the air is a long way from a benchrest.
shooting 400yds from a benchrest with a 3006 is a no brainer but from a tri-pod it's iffy at best.
 

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ballistic bs

Any other hunters in the area that day? I shoot regular at 350 yards 30/06 150g handloads zeroed at 200 yds, aprox 12" fall
at 350yds. Have not seen a hunting caliber yet that did not require some adjustment, if 200 yd zero was used much beyond 350 yds. But I know there are instances where kills were made at 4-500 yds by hunters. One consideration is what amount(unmarked) of area in a scope = inches or feet at 3-500 yds you do not have to move much for it to be significant distance .Reguardless you did good, you got the deer. For what its worth.

Good Hunting
 
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