Different State - POI Change....is this normal?

[JDD]

Every 20 degrees make a 1 moa change . So you should be 2 moa low.? That does not involve powder sensitivity . It what temp does to air density. You have a competing conditions in attitude would case about 1 moa up. For a net 1 moa low. The 1 inch left could be the influence of wind at new locations

 

[JDD]

Post #3?

Rain has no influence. The bullet displaced air and clears its path. I like shooting in a drizzle makes reading wind easy wipes out mirage

 

[SilverbulletMAG]

Every 20 degrees make a 1 moa change .

Where are you getting that information?

 

[greenejc]

Post #3?

I started contracting in Afghanistan in 2011, and we moved to Colorado in 2014. I used to hunt deer and duck on Ft. Riley every year beginning when I came back from Germany in 1998. I ran or cleared all the ranges except the small and large MPRCs. I shot and ran the POF ranges at least once a month while I was active, and retired in 2003. I miss the hunting and fishing there a lot.

 

[Hookdown]

Post #3?

You mention the word. Not really an explanation. But I stand corrected. It WAS mentioned.

 

[Hookdown]

Rain has no influence. The bullet displaced air and clears its path. I like shooting in a drizzle makes reading wind easy wipes out mirage

Can you provide support for that statement. I'm not claiming it isn't true. But I'm curious as to it's logic. As an engineer, and a pilot, it defies my logic and experience. As a pilot, I don't think water droplets could move fast enough to get "cleared" out of the path. I've been in supersonic jets and got water on the canopy going through rain. Would that be through vaporization, or pushed by the pressure wave, or what process? And as an engineer, I know there is no free energy. Even the act of vaporization or pushing anything, in any way, takes energy. That energy would have to come from the bullet, which would impart a negative trajectory on it. But I could be wrong.

 

[WY02K]

I learned years ago that if you sight in a gun on a wooden bench at the 100 yard range using front and rear bags then shoot off a bipod and a rear bag in the field you will miss at 600 yards on small steel. We went back to the range and my POI was shifted 2-3" using the bipod. I took the bipod off and went back to the 2 bag method and was now back on target. After learning this we tried the bipod and rear bag on the bench vs prone in the dirt and both would group in the same spot, no difference. Then we tried a bipod attached but folded up and used a front bag. POI was virtually identical for all 3 methods with a bipod attached. What I gathered out of all of this is the extra pound attached to the front of the stock was what changed POI. I would guess this would be more or less noticable depending on the quality and weight of the stock. At distances 1000 yards and past you will get a noticeable POI shift depending on how you "load the bipod" as well.

 

[.300 Dakota]

Was normal enough for me to miss the buck of a lifetime high over the back between Coastal MS and the hill country of the OK panhandle...4 times...2 different rifles 3 different deer. I learned the hard way... ALWAYS check your POI when you arrive at a hunting destination beyond, say, 500 miles. I'll probably never see a deer in the 180 - 190 class again.

Hello Fellas,
I am shooting a 7mm Rem Mag 175gr Accubond Lr at 2,850fps.

I sighted in at a 100yard indoor range at 80 degrees in NY at sea level.

I am now in Kansas at 2,100 ft above sea level, in a light drizzle, with 40 degree temp.

So here in Kansas, I fired a 5 shot group at 100 yards and found that my bullets were sub 1/2 MOA just like they were when I sighted in NY but the group was 1" low and 1/2" left.

Do you all think that the difference in weather and altitude caused the POI change?
My gun was in a hard Pelican case so I know that it didn't get banged off zero.

What do you all think?

 

[.300 Dakota]

I shot one ragged hole with a Savage 6 Creedmoor in a freaking Typhoon at the 100yd range, which is the best that gun ever performed. I've always believed rain influenced the trajectory, so I've never shot for groups in even the lightest rain til that day. Maybe I was lucky, but there is evidence of the merit in his statement...

Can you provide support for that statement. I'm not claiming it isn't true. But I'm curious as to it's logic. As an engineer, and a pilot, it defies my logic and experience. As a pilot, I don't think water droplets could move fast enough to get "cleared" out of the path. I've been in supersonic jets and got water on the canopy going through rain. Would that be through vaporization, or pushed by the pressure wave, or what process? And as an engineer, I know there is no free energy. Even the act of vaporization or pushing anything, in any way, takes energy. That energy would have to come from the bullet, which would impart a negative trajectory on it. But I could be wrong.

 

[Gcan]

Hello Fellas,
I am shooting a 7mm Rem Mag 175gr Accubond Lr at 2,850fps.

I sighted in at a 100yard indoor range at 80 degrees in NY at sea level.

I am now in Kansas at 2,100 ft above sea level, in a light drizzle, with 40 degree temp.

So here in Kansas, I fired a 5 shot group at 100 yards and found that my bullets were sub 1/2 MOA just like they were when I sighted in NY but the group was 1" low and 1/2" left.

Do you all think that the difference in weather and altitude caused the POI change?
My gun was in a hard Pelican case so I know that it didn't get banged off zero.

What do you all think?

I agree bout airlines. The temp could affect more than 2000 feet. Depends on powder. If it still shoot just reset zero and shoot it.

 

[Stiletto150]

My take. Environmental variables have a lot to do with. I also believe your front rest had something to do with it. Not sure if the media(sand, plastic) in the front rests were the same but I have had 1/4" (up or down)shifts using different front bags during load development. a stiff front rest vs a sandbag vs hunting pack is going to have different harmonics and pressures back to the rifle with recoil. I also have noticed that if I have too much tension in the sling I pull 1/2" left some times. Post #35 ran the numbers for ya...which match very closely to your results.

 

[jdavistx]

1/2 MOA difference at 100yards based on environment? Maybe. 1/2 MOA is 1/2" @100. 40deg temp differential. Temperature of your load? Humidity, ? vs drizzle. 2100 ft altitude differential. Indoor (bencherest?) vs outdoor(?). Wind? I'm not saying that's the problem but they all add up.

However, to answer your question directly there are some really good programs out there. I happen to be a big fan of Brian Litz - Applied Ballistics. It doesn't come cheap but there are some free ones on the web, although not as good. I use a Kestrel to collect my data.

If it's not the gun or you (sorry), take the environmental conditions in both places and run them through a ballistic calculator. That will give you a clue. I live in Texas and elk hunt in Colorado. Sometimes some weird stuff happens and I have to chase it down.

Last question: Is this factory ammo or handholds. Sometimes you get strange results from box to box. The biggest opportunity for me is to make sure that I shoot 0.004" off the lands. So I do handloads.

Like your choice of weapon I shoot a 7mm Rem mag and use 168gr hunting VLD's from Berger. 2995fps. 0.258 MOA.

I wish you well in your search for the solution.

JD

 

[Stiletto150]

I am not sure where the Hill Brothers got there info but I have seen very similar from a lot of different books. This shows temp can change your POI 2 MOA down and altitude can change .5 MOA up. I want to say from recollection these are based around the 308 cartridge. My guess is humidity had a little to do as well. Indoors maybe 60%RH and outdoors in drizzle 99%RH. And high humidity/rain can move impact up as well.
https://www.hillpeoplegear.com/Education/Articles/Rifle-Cheat-Card

 

[arch408]

maybe cuz most of New York is high and too far to the left!