Thread: Downhill shot

I have never been in the situation where I had to shoot at long hunting range 300m+ downhill. I'm planning a trip where I will probably be in such situation.
I have been playing with the Hornady 4dof app and Ballistic advanced edition:
Both give the exact same elevation at 300m and 0deg (1.65 mrads).
However the Hornady 4dof app give only 0.98 mrads of elevation at 30deg while Ballistic AE gives 1.28 mrads.

Using the Rifle's man rule (cosine30deg x 300=260m) to get the true ballistic range (TBR) I get 1.26mrads. Ballistic AE result is pretty close.

Did anyone managed to practice at angle and compare shot with the Hornady 4dof? I have been using Hornady 4dof at the range, it is pretty much always bang on. I have no way to practice at angle, it would be great to know if the app is accurate enough at angles or can't be trusted.

Wanna post up your ballistics? Bullet, BC, velocity, atmospherics, etc? I'll put it into strelok and see how it compares.

Should be drop for 260 but windage for 300

Originally Posted by Pommy

Wanna post up your ballistics? Bullet, BC, velocity, atmospherics, etc? I'll put it into strelok and see how it compares.

Sure, I used the same date in Ballistic AE and Hornady 4dof:

BC 0.646 (Hornady 6.5mm 140gr ELDM
2500fps
100m zero
sight height 2"
Barrel twist 1:8

atitude 0
temp 20degc
humidity 60
pressure 1013.31
wind speed 0

I get 1.3 MRAD. That's rounded to 1dp.

cheers, that's really close to Ballistic AE. Not sure what's happening with Hornady 4dof

Hi Tibo
Just put your data through my ballistic app and at 260m on the flat it calculates -1.1 mil. I think they are all guesstimates, my app is Exterior Ballistics. If you sighted in at 200 the drop at 300 would only be 9.1", and the 300m (260m) shot downhill only -4.6" low, meaning your aimpoint adjustment would be minimal.
Cheers
Ruger7mm

point and shoot.....job done.

Originally Posted by Ruger7mm

Hi Tibo
Just put your data through my ballistic app and at 260m on the flat it calculates -1.1 mil. I think they are all guesstimates, my app is Exterior Ballistics. If you sighted in at 200 the drop at 300 would only be 9.1", and the 300m (260m) shot downhill only -4.6" low, meaning your aimpoint adjustment would be minimal.
Cheers
Ruger7mm

hum... at 0deg both Hornady and Ballistic AE give me 1.28 mil at 260m. At 0deg these two app give me bang on the same table, no issue there. They also seems super accurate a 0deg. See below picture my zero at 100m for a new load then went 1.69 mils up and shot this group at 300m. Hornady app seems to get off track for some reason when angle increase.
What app are you using @Ruger7mm

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.

Originally Posted by Micky Duck

point and shoot.....job done.

Oh fuk yea. At that range down hill shot I've never taken any ballistic measurements, just centre cross hairs click bang dead deer. Obviously not head shots but broadside it's a big target.

Na I need the accuracy I like to eat fawn

Originally Posted by tibo

Na I need the accuracy I like to eat fawn

Ive shot hares with .270 between 400-500yards downhill...much further than Ive shot at big game....its surprising how little a bullet drops....rough guide is you use same drop as if you were shooting to spot out in direct line horizontally to above the animal.fawn sure tastes good,poke bullet into the crease.its still a 6" target area.

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