Level Rifle when Zeroing?

[FourT6and2]

I hit up the range and zeroed my new scope this past weekend. And everything seemed pretty good. But I just realized that the rifle itself wasn't level when I did so. It was level when I mounted the scope and everything. But the range only allows you to shoot from a a bench. And their benches and the targets are at different elevations. i.e. targets are all basically on the ground. So you're shooting at a downward angle. Will this affect the zero?

If I level the rifle I'd have to find a way to get the rifle and the target at the same elevation, which I don't think is possible at this particular shooting range.

I wonder if this is why I was hitting bullseye at 50 yard zero, but like 6" high at 100 yards (XM193 ammo), instead of the typical 1.4 - 2 inches high shown in shooting charts?

[Idaho_slim]

What optic? 6" difference/50 yards is drastic.

[SuperSet]

You'll always shoot high when at an angle uphill or downhill so you should aim low, when enough distance and angle is involved. At 100 yds, that's too small of a distance. Rifleman's Rule:

"
Originally Posted By Q-Man:
It's a pretty well-known aspect of ballistics that shooting at up-hill or down-hill angles both reduce bullet drop. I believe the approximation known as the "rifleman's rule" states that you set your bullet drop compensator on your scope/sights to be equal to the line-of-sight distance to the target multiplied by the cosine of the up or down-hill angle.

for example, you measure a target 100 yards away with a laser range finder. You are going to be shooting 20 degrees up-hill. Therefore you set your sights as though you were shooting at 100-yards * cos(20-degrees) = 94 yards.

You measure 200 years to a target with a laser range finder. You are going to be shooting 30 degrees down-hill. You need to set your sights as though you were shooting a distance of 200-yards * cos(30-degrees) = 173-yards."

[FourT6and2]

Optic is Kahles K16i.

I basically just threw the rifle in a rest and zeroed for 50 yards with XM193, 16" barrel, 1:7 twist. Was dead on at 50 yards. But target was ground level. Rifle was on a typical bench. So shooting downward. 100-yard target was higher since you're shooting over the 50-yard one. So 100 yard target was probably up around 6 feet or so off the ground. And I noticed that at 100 yards, POI was about 6 inches high. All the info/charts I've seen put POI @ 100 yards with XM193, 50-yard zero at 1.4" or so high, not 6".

So if shooting downward reduces bullet drop, then could that explain why I was shooting high at 100 yards?

[SuperSet]

That angle and distance won't make that much difference. That quoted example shows a 20 degree angle showing a difference of 94 yds vs 100 yds.

One thing you should note is that when shooting non match ammo, you're looking at an average accuracy of 3MOA or 3" at 100yds. Shoot a 5-10 shot group so you can find an average for the actual zero center.

[FourT6and2]

That angle and distance won't make that much difference. That quoted example shows a 20 degree angle showing a difference of 94 yds vs 100 yds.

One thing you should note is that when shooting non match ammo, you're looking at an average accuracy of 3MOA or 3" at 100yds. Shoot a 5-10 shot group so you can find an average for the actual zero center.

Oh I did. I was shooting 10-shot groups. Hell, I even did a 150-round group at 50 yards But at 100 yards, groups were about 6" high on average. 3 MOA @ 100 yards seems pretty tough for me at the moment. I'm getting about that at 50 yards.



At 100 yards, I had to put POA a few inches below the bottom of the shoot-n-see target to get impact in the 10-ring.


This one is about 2 MOA @ 50 yards.

[GoatLocker]

Did you change anything on the scope between the 50 and 100 yd shots? Change focus, magnification, mess with the mount? Did you go back to 50 yds and verify zero after shooting high at 100?

[SuperSet]

What is your final zero going to be? 200 yds? If yes, shoot at 200yds and see the actual zero and spread and adjust from there.

[FourT6and2]

Did you change anything on the scope between the 50 and 100 yd shots? Change focus, magnification, mess with the mount? Did you go back to 50 yds and verify zero after shooting high at 100?

I don't believe I changed anything on the scope. Definitely didn't touch the turrets (they were kept capped). Might have zoomed out and then back in at some point. But that shouldn't make a difference, right? If so, I would assume something was wrong with the scope. All shooting was done at 6x. Didn't touch the mount.

I don't think I went back to 50 yards though. I will hit up the range again this weekend and reverify.

What is your final zero going to be? 200 yds? If yes, shoot at 200yds and see the actual zero and spread and adjust from there.

The range I go to only has two shooting distances: 50 yards and 100 yards.

[GoatLocker]

Might have zoomed out and then back in at some point. But that shouldn't make a difference, right?

It shouldn't, especially an a high end scope like yours, but it seems to me something changed between the time you shot at 50 and 100.

[SuperSet]

The range I go to only has two shooting distances: 50 yards and 100 yards.

The reason I ask is that I never completely trust the near zero. A lot of folks say that 50 is the same as 200 and I always zero at the far zero for the actual zero and just accept that the near zero is 'near enough'.

[Full Clip]

Optic is Kahles K16i.

Yikes, nice.

[NytWolf]

Don't worry about rifle tilt or elevation change until you consider your ammo ballistics.

[FourT6and2]

The reason I ask is that I never completely trust the near zero. A lot of folks say that 50 is the same as 200 and I always zero at the far zero for the actual zero and just accept that the near zero is 'near enough'.

Yeah, I wish I had a range that went out farther. There is a 200-yard one around here. But the range is only open on Friday mornings (WTF!). I think there might be another 200-yard range nearby too. But you have to be a member to shoot there. I might look into that one.

Yikes, nice.

Yeah, when I do something I kinda go all out the first time around. I think I started out looking at like $500 scopes. But quickly upped my budget after doing some research into what I wanted.

It shouldn't, especially an a high end scope like yours, but it seems to me something changed between the time you shot at 50 and 100.

Ok, well I will head back out to the range this weekend. I'll be more systematic about what I'm doing to double check POA/POI. Just to clarify, though:

16" barrel
1:7 twist
XM193 55gr
50-yard zero

POI should be about 1.5" - 2" high @ 100 yards (notwithstanding wind and temp. and humidity, and so on)?

I also have MK262 Mod 1 77gr. Trajectory will be different on that one. I'm still trying to track down a chart for this ammo.

[l8apex]

The reason I ask is that I never completely trust the near zero. A lot of folks say that 50 is the same as 200 and I always zero at the far zero for the actual zero and just accept that the near zero is 'near enough'.

^This, I zero at a hundred and believe the same mantra. You have to zero at the actual distance. My parter attempted to zero at a near distance and had a similar experience. Turned out he needed to tighten down his mount slightly and rezero. The 50 wasn't quite there but the 100 was spot on.