Fired a bit more of the 175gr subsonic ammo ... having a some trouble with my NVD, but the below shows it is possible for me to shoot a very different round and very different ranges from what I'm zeroed at and it shows the elevation required to use the 175gr(subsonic) ammo is very manageable out to 200yds. Should be manageable beyond that, probably even to 300yds, don't have to worry much about wind!
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Attempt to calculate adjustment from 147gr ammo zero to 175gr subsonic.
Assumption: Zeroed at 325 yards with 147gr ammo.
Need to hold down 1.2 mils to hit at 50yds with 147gr ammo.
From 50yd zero need to hold up 4.7 mils to hit at 150yds with 175gr subsonic ammo.
So net need to hold up 3.5 mils to hit at 150yds with 175gr(sub) ammo.
From 50yd zero need to hold up 7.5 mils to hit at 200yds with 175(sub) ammo. So net need to hold up 6.3 mils to hit at 200yds with 175(sub) ammo.
1 mil at 150yds is 5.4 inches
1 mil at 200yds is 7.2 inches
We need to cover 25 inches of drop at 150yds. (4.7 mils) minus 1.2 is 3.5
We need to cover 54 inches of drop at 200yds. (7.5 mils) minus 1.2 is 6.3
If using 3.5x magnification. Then
holding down 1.2 mils to get to 50yds will be .42 mils down.
holding up 4.7 mils will be 1.645 mils up, minus .42 is 1.225 up for 150yds
holding up 7.5 mils will be 2.625 mils up, minus .42 is 2.205 up for 150yds.
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2014-01-28
1400-1500
20F wind 10 mph SW
Fired 4 rounds 175gr(subsonic) switched scope to 3.5x magnification as I will be using this at night.
Results
150yds
First round POA center of bull holding 1.25 mils up, no windage. POI on orange dot 6 inch down and right from bull. This is 4 inches low and 4 inches right.
Second round holding 1.75 mils up, .5 mils left. POI 1.5 inches down and left of bull. This is within 1 MOA of the bull.
200yds
Third round holding 2.5 up .5 left. POI on green dot 3 inches high directly over the bull. This is 1.5 MOA from the bull
Fourth round holding 2.25 up .5 left. POI 2 inches low and right from bull. This is 1 MOA from the bull.
So it looks like we can do fine at 200yds with the 175(sub) ammo during the day. We will try to repeat this test tonight with the NVD.
Here is target pic
So question is why did my arithmetic not work for the 150yd initial shot? I thought I needed to hold up 1.25 mils but in reality I had to hold up 1.75 mils.
At 200yds, I had pre-calculated I needed to hold up 2.25 mils and in the event that was correct.
Why did my pre-calculated arithmetic seem to work for 200yds but not for 150yds. I'll have to redo the calculations and see if I can find an error.
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2014-01-28
Night
10F
wind 5 mph S
Fired 2 rounds 175(sub)
Results
150yds
First round POA center mass of target, could not see bull. Was firing with IR off. Turning IR off lite up too many nearby blades of grass and I could not see target. Round impacted high right 9 inches from bull. Was holding 1.75 mils up and no windage.
Second round POA center mass of target. Holding 1.75 mils up and no windage. POI high right 9 inches from bull.
Here is target pic
Is the "collimnation" problem back again? To establish this I will have to switch lots of things around. I will need the 10x Luepold scope on the .22LR and the 20x scope on the 7.62 ... only the 10x scope can easily mount the NVD and I don't want to spend 7.62 rounds figuring out whether the NVD is off again. Good news is I did score 7 boxes of 325 rds of Federal AM222 today, price was higher than I wanted to pay 11 cents a round, but having 2275 rounds of AM22 should hold me for a year and the guy threw in 50 rounds of Remington subsonic as well, so I'll have something for pre-zeroing.
I'll have to tear down the .338LM to do the above changes, so I'll go shoot it out at 600yds one more time before I do tear it down. If I have to replace the PS22 with something new, that will also cause a major rearrangement of my one time, last time (major new item acquisition) shooting budget for this summer. I might have to give up the S&B scope I wanted

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Day
2014-01-29
0800-0900
10F
wind 10 mph SSW 250 degree with respect to bullet path for this FP.
Fired 2 rounds 175(sub) from 150yds.
Here is target pic.
Purpose of this exercise was to re-verify that holding 1.75 up and in this wind .5 left gets close to the aiming point, within 1.5 MOA in this case. I was in a hurry as I need to be working by 0900 and spotting scope fogged/froze up (not water proof) so had to hoof down to the target and back before the second round. So second round farther away that it should've been.
Anyway, before I "panic" and tear everything down, I will try again tonight with the PS22. Last night, after RTB, I realized I did not focus the NVD. I am hoping that matters and I will try that tonight. I should be able to at least see the (black on white) bull. I used to be able to and I could not last night. So that makes me think/hope the NVD was not focused. So will try again tonight.