FAIL... confusing POI/POA between stages

[J.Boyette]

akula88,

I run the same ZERO in my DPMS LR-308 shooting 168's at 2650fps.

BUT the below nunbers are not from a chart. These are TRUE POA/POI hits on paper and steel. I have been testing this for 2 weeks now and have shot over 400rnds for these numbers.

I think you need to FULLY understand how the bullet gets from point A to point B and not use computer charts 100%. You need to go shoot it for real.

The holds are simple.

Key:
Hold Under = HU
Hold Over = HO
Inches in Relation to Line of Sight = IRLOS

010yds 1.4milrad HO IRLOS 1.5” low
020yds 0.8milrad HO IRLOS 1.1” low
030yds 0.2 milrad HO IRLOS 0.6” Low
040yds ZERO IRLOS 0.0
050yds ZERO IRLOS 0.0
060yds 0.5milrad HU IRLOS 1.1” high
070yds 0.5milrad HU IRLOS 1.3” high
080yds 0.5milrad HU IRLOS 1.4” high
090yds 0.5milrad HU IRLOS 1.6” high
100yds 0.5milrad HU IRLOS 1.8” high
110yds 0.6milrad HU IRLOS 2.4” high
120yds 0.6milrad HU IRLOS 2.6” high
130yds 0.6milrad HU IRLOS 2.8” high
140yds 0.5milrad HU IRLOS 2.7” high
150yds 0.5milrad HU IRLOS 2.6” high
160yds 0.4milrad HU IRLOS 2.3” high
170yds 0.4milrad HU IRLOS 2.1” high
180yds ZERO IRLOS 0.0
190yds ZERO IRLOS 0.0
200yds 0.1milrad HO IRLOS 0.75” low
210yds 0.1milrad HO IRLOS 0.8” low
220yds 0.1milrad HO IRLOS 0.8” low
230yds 0.2milrad HO IRLOS 1.75” low
240yds 0.2milrad HO IRLOS 1.75” low
250yds 0.4milrad HO IRLOS 3.6” low
260yds 0.5milrad HO IRLOS 4.75” low
270yds 0.6milrad HO IRLOS 5.8” low
280yds 0.6milrad HO IRLOS 6.0” low
290yds 0.8 milrad HO IRLOS 8.4” low
300yds 1.0milrad HO IRLOS 1.08” low

Using this 40yd ZERO on a SWS for deployment setting from trunk of a car / truck to FFP is the way to go it looks like. The worst offset was at the 10yd line but even that came at the 6 o'clock location in the T-zone. By aiming center mass as it stands right now I can shoot within a 6" target from 0 to 240yds. The highest place of my bullet is at 130yds and its right at 2.8" high then drops off at 240yds at 1.75" low.

So what nice about this is that with different target sizes my life gets real simple.

Target face surface area aiming center-mass:
0yds to 240yds POA / POI high low with in 6”
0yds to 250yds POA/POI high – low with in 8”
0yds to 260yds POA/POI high – low with in 10”
0yds to 270yds POA/POI high – low with in 12”
0yds to 280yds POA/POI high – low with in 14”

Granted, running any ZERO distance you can do the samething to a point. But the ability to engage target sizes at distance drops off.

From what I have found, the 40yd ZERO gives the best of both worlds. As a LEO Sniper lets say, you can engage all the target sizes above as a deployment ZERO.

Once onsite you can dial in the right DOPE for the suspects engagement zone, this ZERO lets you move from point A to point B with the ability to raise the hit rate % drastically over a 100yd ZERO.

John

[SA80Dan]

I have to agree - getting you out of your comfort zone can be a killer. I've seen as much as 1 MOA difference when changing from a sandbaged bi-pod zero to prone with a bi-pod.

A 40m zero does equal a 200M zero for my 77 gr SMK load at 2,700 fps with a sight height of 2.6" - although I would only trust the rifle when actually zeroed at 200. And 2" high at 100M is correct as well.

Try to replicate the shooting position on your home range and see what happens. A chronograph check would be advised as well.

I think this says 99% of it. While you can approximate a zero with charts and tables, there's no substitute for confirming the real thing. The other part of this (and I dare say probably the biggest part) is going from a zeroing environment to a pressure timed competition one with unstable barricades, awkward firing positions/ports and what have you. Sometimes (on off days) the best zero in the world doesn't even help in those circumstances.....

[shootist~]

...my second stage which was done with a 30-rdr mag as support (bipod is forbidden in this stage), similar POI/POA differentials happened.

Same thing here. Prone/mono-pod on a magazine is going to change the POI. Generally a little lower than a benched sight-in (usually 1 MOAish for me), but my DD LW will move ~2 MOA down an some off to the right as well. Optic in this case is a Micro Aimpoint.

Optic settings can change thing as well. My PST 1-4 at 1X has a difference of ~1.25" at 85 Yds (higher) than at 4X (both prone/mono-pod on firm sand).

[Failure2Stop]

Which optic do you have, and by what measure are you determining your hold-off?

This leads to another vote for the possibility of sub-optimal assumption of zero.

And with that level of disregard for something so essential to rapid mid-range performance I would have to assume that this is a new level of competition for you and you may have not performed to your best. Sometimes that performance drop is due to underappreciation of sight picture, and sometimes it is overconfidence in cadence. I know it has happened to me and lots of other newer competitors, even guys with significant combat experience.

I think you are in need of some good classes to perform as you desire.

[Todd.K]

I used PointBlank/6mmmbr.com trajectory to compute for the approximate 200-meter zero

Did you measure you scope offset or use the default in the program?