Thread: Downhill shot

Originally Posted by Micky Duck

point and shoot.....job done.

You're showin your age Mick - its a lot more complicated that that these days, and thats why you need your iphone before you make the shot.
Just as well the deer aren't in a hurry no more

Verify by shooting it too. The effect of angle (either uphill or downhill) is to reduce the horizontal range that gravity has available to drag the pill down, that's why a lot of the ballistic apps give you the correction in MOA/MIL and also in effective ballistic range. To check your drop on the flat (as most ranges are on the flat and can't simulate an up or down angle) set your target up at the stated intermediate range and confirm you're on zero at the given MOA/MIL adjustment.

As noted above, your time of flight is the same as the actual range you are shooting at so windage corrections are for the actual range not the corrected (shorter) ballistic range adjusted to correct for the angle.

I'm not a long range shooter but surely you just need TBR and that will give you what you need right?

From Kestrel 5700 AB

Baseline data
Gun
MV	2500fps
BC G1	0.646
BW	140gr
BD	0.264 in
ZR	100m
BH	2.00 in
Twist	1:8.00 in R
Enviro
Wind	0.00 MPH
Lat	-40 degrees
Temp	20 Deg Cel
SP	29.92 inHg
RH	60%
D/A	763ft

Distance (m)	0 Degrees Mil Hold	Hold in cm	+30 degrees Mil Hold	Hold in cm	-30 degrees Mil Hold	Hold in cm
100	0.00	0	-0.12	-1	-0.12	-1
200	0.70	14	0.45	9	0.45	9
300	1.65	50	1.27	38	1.26	38
400	2.73	109	2.21	88	2.19	88
500	3.94	197	3.26	163	3.22	161
600	5.27	316	4.42	265	4.36	262
700	6.74	472	5.70	399	5.62	393

Originally Posted by JT_NZ

From Kestrel 5700 AB

Baseline data
Gun
MV	2500fps
BC G1	0.646
BW	140gr
BD	0.264 in
ZR	100m
BH	2.00 in
Twist	1:8.00 in R
Enviro
Wind	0.00 MPH
Lat	-40 degrees
Temp	20 Deg Cel
SP	29.92 inHg
RH	60%
D/A	763ft

Distance (m)	0 Degrees Mil Hold	Hold in cm	+30 degrees Mil Hold	Hold in cm	-30 degrees Mil Hold	Hold in cm
100	0.00	0	-0.12	-1	-0.12	-1
200	0.70	14	0.45	9	0.45	9
300	1.65	50	1.27	38	1.26	38
400	2.73	109	2.21	88	2.19	88
500	3.94	197	3.26	163	3.22	161
600	5.27	316	4.42	265	4.36	262
700	6.74	472	5.70	399	5.62	393

Interesting, I haven't seen such a big difference between up angle and down angle as in that table before. Dunno what that means, guess you'd need to check it and verify it by shooting. There was a manual device in the past called a 'Mil Dot Master' that used a string and a weight to give you the angle then that gave you a correction for range as estimated off the mildots in the scope. Surprisingly accurate to be fair, but a wee bit of fluffing about to achieve the corrections...

Originally Posted by JT_NZ

From Kestrel 5700 AB

Baseline data
Gun
MV	2500fps
BC G1	0.646
BW	140gr
BD	0.264 in
ZR	100m
BH	2.00 in
Twist	1:8.00 in R
Enviro
Wind	0.00 MPH
Lat	-40 degrees
Temp	20 Deg Cel
SP	29.92 inHg
RH	60%
D/A	763ft

Distance (m)	0 Degrees Mil Hold	Hold in cm	+30 degrees Mil Hold	Hold in cm	-30 degrees Mil Hold	Hold in cm
100	0.00	0	-0.12	-1	-0.12	-1
200	0.70	14	0.45	9	0.45	9
300	1.65	50	1.27	38	1.26	38
400	2.73	109	2.21	88	2.19	88
500	3.94	197	3.26	163	3.22	161
600	5.27	316	4.42	265	4.36	262
700	6.74	472	5.70	399	5.62	393

The slight difference you see here in predicted holds between uphill and downhill is primarily a result of the Kestrel AB engine taking into account the difference in air density across the predicted flight path of the projectile. This is only a factor in extreme situations. As mentioned by others, for 95% of NZ hunting situations, basic horizontal range should be fine.

Note: you still need to account for aerodynamic jump. This and other factors such as incorrect range measurement, incorrect angle measurement, parallax, etc. could explain some of the observations where there has been a vertical delta between expected fall of shot and actual fall of shot. Some of these errors may not be the fault of the firer. For example, I have had three different LRF Binos in the mountains at one time when hunting with a party, and whilst they all provided similar distance to target, some had significant differences in measured inclination angle.

Woaahhh way too much info!
Draw a triangle. It's the horizontal axis that is the true ballistic distance.

Geez I can't understand why all the confusion over a 300yard shot, my range finder has TBR so I just use the TBR corrected distance it gives me and it's been good enough, I shot a spiker last week decent downhill angle at 400yards hit it exactly where I wanted.
Mate shot a stag same trip 682yards very steep uphill shot and tbr range was spot on too.
Am I missing something ?
We dial for our shots not holdover just for clarity

Originally Posted by dannyb

Geez I can't understand why all the confusion over a 300yard shot, my range finder has TBR so I just use the TBR corrected distance it gives me and it's been good enough, I shot a spiker last week decent downhill angle at 400yards hit it exactly where I wanted.
Mate shot a stag same trip 682yards very steep uphill shot and tbr range was spot on too.
Am I missing something ?

Some people overthink things and make mountains out of molehills. Get fecking closer, you have to recover animal anyway, or man-up and pass on the shot.

Originally Posted by woods223

Some people overthink things and make mountains out of molehills. Get fecking closer, you have to recover animal anyway, or man-up and pass on the shot.

I wouldn't have thought a 300y shot was that far to consider passing up, easily ethical with most centerfire offerings for example; a 270win with standard 130gn interloks zeroed at 200y is only 6" low at 300y, a good rest and holding a little high would easily see you sorted.
I do agree with the comment "get closer if you can, as you point out you've got to recover it anyway."

Originally Posted by dannyb

I wouldn't have thought a 300y shot was that far to consider passing up, easily ethical with most centerfire offerings for example; a 270win with standard 130gn interloks zeroed at 200y is only 6" low at 300y, a good rest and holding a little high would easily see you sorted.
I do agree with the comment "get closer if you can, as you point out you've got to recover it anyway."

300+ + being the OP comment but agree with you.

Some interesting stuff here for those who like to understand how things work
https://www.sierrabullets.com/exteri...inclined-fire/

There will be a slight difference between uphill and downhill. Uphill is going against gravity so will slow down a bit more, downhill is going with gravity so will slow down slightly less.

Originally Posted by stug

There will be a slight difference between uphill and downhill. Uphill is going against gravity so will slow down a bit more, downhill is going with gravity so will slow down slightly less.

Actually wrong. Plug it into a calculator. At a given angle the corrections will be the same whether it's up or downhill. It's the angle from horizontal that's important, not the direction. That's why BDX style rangefinders also measure the angle.

Identify your target beyond all doubt because you never miss (right?) and I'll be missed.

Originally Posted by Eat Meater

Actually wrong. Plug it into a calculator. At a given angle the corrections will be the same whether it's up or downhill. It's the angle from horizontal that's important, not the direction. That's why BDX style rangefinders also measure the angle.

Identify your target beyond all doubt because you never miss (right?) and I'll be missed.

Calculators aside, how can that be, a bullet surely must have an advantage going downhill as opposed to up. A bullet not shot but dropped from the top of a cliff will accelerate to TV in free fall. A bullet is never going to fall upwards ( on earth) so the difference between the two is real