Hold over/under question

[LDB415]

I'm reading a book with a scene making a rifle shot about 350 yards at a target 60-80 feet lower than the shooter. It goes through thoughts and calculations of trajectory and concludes that would put him about 9 inches low and 4 inches to the left due to a slight breeze. Then it says so he had to hold 9 inches low and 4 inches to the left.

So my questions are:
1. What effect does shooting downward have on trajectory as opposed to shooting at a target straight out from the shooter?
2. If he is going to be 4 inches to the left due to the breeze how is holding 4 inches to the left going to help?

[allisji]

I could be wrong, but it sounds like the writer probably doesn't have much of a background in math or shooting.

As far as the slope is concerned that equates to about 1 ft of elevation drop per 13 ft of horizonatal distance which is not insignificant, but is a mild sloping hillside.

The bullet drop from point of aim would be almost the same as shooting at a target 350 yards away on a level plane I would imagine.

[PriestTheRunner]

I'm reading a book with a scene making a rifle shot about 350 yards at a target 60-80 feet lower than the shooter. It goes through thoughts and calculations of trajectory and concludes that would put him about 9 inches low and 4 inches to the left due to a slight breeze. Then it says so he had to hold 9 inches low and 4 inches to the left.

So my questions are:
1. What effect does shooting downward have on trajectory as opposed to shooting at a target straight out from the shooter?
2. If he is going to be 4 inches to the left due to the breeze how is holding 4 inches to the left going to help?

Ya thats written backwards, lol.

As far as shooting downwards, I don't have a ton of experience with terrain range shots but inside of 500 yards I did not think it made a difference?...

Maybe one of the long shooters on the board can clarify the elevation aspect.

[Lynyrd]

Of course it depends on what distance your sight is zeroed at, but shooting downhill you will tend to hit high. I think your author got their words twisted a bit, but you would have to aim a bit low when shooting downhill. 9 inches sounds a bit much at 350 yds, but it depends on the round and where the sight was zeroed.

[allisji]

Of course it depends on what distance your sight is zeroed at, but shooting downhill you will tend to hit high. I think your author got their words twisted a bit, but you would have to aim a bit low when shooting downhill. 9 inches sounds a bit much at 350 yds, but it depends on the round and where the sight was zeroed.

I would imagine that whether you're shooting downhill, uphill, or level that you would first fix your point of aim on your target, and next adjust a little higher to correct for bullet drop.

If you are shooting at something that is elevated, I would assume the projectile will lose more energy than normal because it has to fight gravity. If shooting at a target that is at the bottom of a hill you would lose less energy than normal because the projectile is traveling in the direction (partially at least, because you aren't firing straight down) of the gravitational force.

It's been awhile since I took phsyics (~14 years), so my logic may have some flaws, but I think it makes sense.

[Bitter Clinger]

http://www.rifleshootermag.com/network- ... ngle-shot/

[EODgunner]

So yes, if you are shooting down and your rifle is sighted in for say 300yards then your going to have to aim low. With the data given (350 yards and 80ft lower) there is no need to hold for an adjustment like that. If it was 350 YARDs down and 80 yards out from your position then you might see a crazy need to aim low. Hell, I’m sure your average deer hunter has made 350 yard shots and never noticed or accounted for a drop that was as little as 80ft. I’m sure elk hunters shoot from one ridge to another with a lot more drop then that and never need to account for it.

This is all based on the idea that the rifle is zeroed at say 100 or 300. If it were sighted in at something crazy like 600 then you would have to hold low just because of that at shorter distances

[LDB415]

Ok, so if I am understanding correctly the part about holding low is correct. What about the holding left? It says the wind would push the round about 4 inches to the left and then it says he needs to hold low and to the left. Wouldn't he need to hold to the right to offset the wind pushing it left?

[Mike S]

More accurately, the part about holding low 'could be' correct, depending on the distance the rifle was zeroed for. I'm thinking the author just got it backwards. It takes a pretty significant slope angle and a significant distance to really require much adjustment for slope. Uphill slopes & down hill slopes are calculated the same.

For winds, if the wind is blowing FROM the left, you would hold TO the left. (Holding into the wind).

Even more indicative of the author not really having a foundation of precision marksmanship would be his use of 'inches' in relation to the corections needed. Corrections are usually calculated for the type reticle (MILs or MOAs), not inches.

[LDB415]

It says "... a slight breeze, would move the bullet as it traveled perhaps four inches to the left. So he had to hold nine inches lower and four inches to the left." I take that as a wind from the right pushing the bullet to the left. It seems it would require holding to the right not the left so when the breeze pushes it left it will wind up spot on.