MATH RIDDLE: sight adjust from 5m to 10meters

[wasatch]

So i cheated and used the Hawke Optics software Chairgun Pro. Configured for RWS Hobby pellets shot at 500fps (152.4m/s) with a sight height guess of 1.27cm (0.5") and a 5m zero the POI at 10m is 0.5mm high. Almost a double zero at those distances assuming the sight height is correct...

I'm not sure about the sight height setting since this software is for shooting with scopes with parallel offsets where the desired outcome is generally POI = POA. Am i correct thinking that Sub 6 hold introduces an angular offset that should be constant when using correctly scaled targets at various distances. Thoughts? Angular offset might be affected by less bull blur at 5m & more blur at 10m resulting in lower POI at 10m...

If sight height is set to 0.0 with 5m zero the POI at 10m is -12.2mm.

FWIW, I practice with my P8X (RWS Basic 7gr, 164.6m/s) at 7m with 42mm dia target then shoot standard 59.5mm targets at 10m and make no adjustments. When i plugged those numbers into Chairgun (zero at 7mm, 1.27cm sight height) the POI at 10m was 0.9mm low. I'm not good enough to notice.

[atomicgale]

Wasatch,

Please re-run your software with the following adjustments:

Sight height = 16.5mm (0.650")
Incline = 0.511degrees
Start range = +0.7 meters (muzzle is extended past 10meter line)

Adding-in the Sub-6 hold dimension, I solved for angle of Barrel vs. Line-of-Sight, and got +0.511-degrees, with a Sub-6 hold using the 6-Ring as base.

My pen & paper method yielded: Pellet strikes 10-meter target +11.89mm high.

(Hence, 10 clicks to "H" on Steyr EVO.)

[wasatch]

Unfortunately in ChairGun the incline minimum increment is 1 deg (and is for shooting at elevated targets as in field target).
Start range min increment is also 1 yd.

My thinking is:
The barrel axis has to have a positive incline so that the ballistic trajectory will intersect with the bull.
The sight line is fixed and doesn't change at various ranges assuming same hold (sub6), no change in blur at various distances, using correctly scaled targets and the reduced range target is at the correct height.

So to re-zero at various distances rear sight clicks are altering the barrel incline to raise or lower the POI while POA is constant.
For a 10m AP, whether POI needs to be raised or lowered when re-zeroing from 5m to 10m depends largely on muzzle velocity.
Holding the other characteristics constant, at ~131m/s there's a double zero at 5m & 10m.
Shoot faster (152.4m/s or 500fps for example) the 10m POI will be ~4mm high when zeroed at 5m.
Shoot slower (110m/s for example) the 10m POI will be ~7mm low when zeroed at 5m .

Side note: effect of increasing blur at further distances (or varying brightness) isn't negligible. Actual re-zeroing clicks for you will most likely also be affected by change of blur unless adjusting eyewear (diopter/iris) to keep constant blur.

[Rover]

Knock off the bullshit and just shoot some sighters as described in my post above.

I've never seen such drama on here over a couple of clicks of elevation.

[atomicgale]

Rover, this is not "Drama"; this is SCIENCE.

Addressing your "Shoot some Sighters" recommendation, the pros/cons of the SCIENCE vs. SIGHTERS approach is thus:

PRO: The physics approach will dial-in a few clicks of vertical adjustment, yielding confidence in my equipment approaching the next CMP MATCH on October 12th.

CON: The malfunction of the Sighters approach is that I will shoot at least 2,000 rounds in practice between now the match. At the match, I'll get 15 minutes to shoot about 17 sighters. The downfall of the "Shoot some Sighters" technique is that a few sighters may not be adequate to confidently dial-in the pistol. Especially dealing with the nature of human error, to wit: the "I'm in Zone," vs. "I totally Suck," phenomenon.

Also, physics is fun. Of course, Rover, I could always move my home Moonshine Still out of the way & expand my living room range to 10 meters.

For the rest of us . . . sign up here for next CMP MATCH:
https://ct.thecmp.org/app/v1/index.php

[wasatch]

While i agree this is interesting and not simple drama, shooting sighters is the only way to know for sure.

Do a practice match including adjusting to 10m prior to the next match cause there's more to the adjustment than just the ballistics. Lighting differences will impact elevation as will the difference in blur for you between 5m and 10m. If you can't, then oh well, hang your hat on the math and hand wave at the other factors.

What sighter routine do you have? I warm up & dry fire at the back of a target. Then shoot 5-7 sighters w/o checking each impact, just trying to focus on doing the same thing each shot. Then check the location of the group and adjust. Then shoot another round of sighters w/o checking each impact. I feel that if i check each impact while 'sighting' it may influence how i hold from shot to shot. I want to eliminate that possibility so i just shoot 5-7 sighter shots trying to be consistent.

If you're using all the clicks available and focusing on the bull with the front sight blurred you've got bigger things to learn than what the math says.

[atomicgale]

+ 11 clicks on Steyr EVO:

[atomicgale]

Trying to get Dialed-in again, re-dialing my pistol to 5-Meters (while not over-flying and shooting up my Moonshine Still):
Adjusted the sights, adjusted my gun, and adjusted my attitude.
Back in the fight.