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Discussion Starter · #1 · (Edited)
Today while shooting my 30-30 using Remington cases, CCI 200 primers, IMR 4064 powder, Hornady 110gr FMJ-RN, traveling at an average of 2308fps, with an extreme spread of 12... I noticed my vertical POI was 12 inches lower at 300 yards than it was the last time I shot the rifle with that load.

At first I thought it must have been me missing so I took greater care on my next shot but hit in the same area. The time before it was partially cloudy about 78 degrees with a 10 o'clock 17mph wind; the wind coming up a 12 degree grade.
Today it was almost windless, 58 degrees, cloudy and rainy. This is the first time I have noticed that much of a difference in my vertical POI without having a loss in accuracy. I shoot every day, in every condition; I've even shoot in hale storms.

What i suspect is that I am not used to shooting such a ballistically inefficient bullet, (BC .178,) whereas, all the conditions compounded greatly resulting in a much lower POI; (or higher if the first 300 yard shots were the shots more so affected.) So confusing!
One problem with that theory is, I didn't chrono the shots so i don't know if the temperature had a hand in powder burning slower. Another problem is, I think rainy conditions dictate the barometric pressure is lower, so my POI should be higher. (I checked the weather and am in a low pressure cell.)

Also, if my velocity was slower due to the 20 degree drop in temperature, why was my accuracy not reduced? Ugh; I wish I chronoed those shots!
I am pretty sure humidity has little impact on the POI, I have shot in many a downpour and have noticed little if no difference. Which surprised me greatly.

Same batch of bullets, same batch of powder, same batch of primers, I annealed the cases before the 3rd shot, same cases.

I was wondering if anyone could tell me what might have been the problem. And if weather was the issue, how it might have played a part.
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Illustrations

This is from the last time I shot 300 yards with those bullets.
Here is the target.

The left circle was shot 2 that I thought hit 6 inches more to the left than it did. The right circle is shot 3 holding right 6 inches to try to correct the error. I held the same height both shots and had the sight elevation set on the 3rd notch, top of the sight bead at the top of the target.

Here is today.
Here are the shot impacts from today.

The first two frames are the same sight setting but I held the top of the sight bead in the center of the target. Both hit low about 12 inches.
Shot 3 was after I loaded more ammo, adjusted the front sight left about .012", set the elevation setting on the 4th notch and held the top of the sight bead at the bottom of the target, (I thought it was going to be enough but evidently one click doesn't raise the POA very much.)
The 4th shot is the 5th notch holding the top of the sight bead in the center.
The 5th shot is after another front sight adjust left at .012" and held the same height as shot 4.

I am pretty sure the rifle is preforming wonderfully, my adjustments seem to be resulting in the proper POI.

Thanks for reading!
 

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Discussion Starter · #2 · (Edited)
Update with a Conclusion

I shot it over a chronograph and the velocity was about 80fps slower than when it was 78 degrees.; it was 68 degrees. Velocities were 2248, 2200 and 2244. I am damn sure the powder charges were accurate.

At 300 yards with the same settings as I hit it yesterday, I hit about 2 feet high. The temperature yesterday was 58 degrees, I bet the velocity was around 2150 or so.

I ended up shooting the target at 200 yards and hit pretty well on the 3rd notch, then moved to 125 yards and hit on the 1st notch with the POI behind the sight bead.


My conclusion...
Temperature, those light bullets, the chamber and the powder don't work consistently enough together. I could make them work but that would be a nightmare to figure out a cold bore POI from day to day... seeing 10 degrees could be 2 feet difference.

I think I need some different powder; I used VIHT N 135 with the 110gr V-Max and they seemed to work a lot more consistent. I have just enough powder to preform a ladder test and will probably give it a go sooner or later.

I loaded up some 168gr BTHPs as a ladder test for tomorrow.
 
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