Extreme elevation/climate conditions

[shooterfpga]

Does anyone here shoot in extreme different conditions?

Today i took two of my rifles out to shoot that had been zeroed in texas and then shot in TN. The zeros were way off. I usually get first round hit but never in completely different areas.

It took me awhile to figure out my zeros had shifted because i skipped 100yds and was hitting good at 250. Brought it back to 100yds after i noticed i was 3 mils high at 400 and then i got both my rifles on at 400. I started thinking my firing solution was wrong because i had enabled muzzle velocity and powder temp.

[Fjold]

I zero my rifles at about 500 feet of elevation and regularly hunt at 7,000 feet in Wyoming. I build two drop chart off of JBM and sight my rifle at 200 yards at my home range but I use the data for my hunting altitude. That gets me on paper at 7,000 feet. Then I only need one or two shots at my hunting site to verify the zero.

[highpower790]

From 40ft of elevation to Salt Lake City I need to come up in elevation 3/4 min.

[shooterfpga]

They must have been jarred during transport. Just doesnt make sense theyd be off that much. Ive knocked em around much harder than delicately transporting them and theyve never shifted. Other than that fiasco i was holding 1 moa and 1 1/4 moa @ 400yds and sub moa @ 250.

[shooterfpga]

Cross bolt was at 10in lbs. Guess i need to loctite em.

[dskit]

I've shot all over the country from 15 degrees in Oklahoma in February to 85 degrees at 8,000 feet to 115 degrees at 250 feet and my 100 yard zero has not moved substantially. Getting buped in travel is always a possiblity. I confirm at 100 yards every time I travel.

I only have one zero and that's at 100 yards - my scope reads "zero" at that seting BTW.

My DOPE can changes substantially, expecially past 600 yards in those varying conditions. But my Kestrell with ballistic calculator handles those changes quite nicely.

[Jimi Jah]

I live at sea level. At 12,000 feet in the Rockies my rifles shoot high. A few clicks fixes that.

[kcstott]

Cross bolt was at 10in lbs. Guess i need to loctite em.

Crossbolt on what? the scope rings?? 10in/lbs is light. you need to check your mfgs recommended torque.
Most scope rings with a crossbolt are in the area of 65 in/lbs

Oh and feel free to use loctite. your gunsmith will love you for the return work.

[bigbossman]

I've shot all over the country from 15 degrees in Oklahoma in February to 85 degrees at 8,000 feet to 115 degrees at 250 feet and my 100 yard zero has not moved substantially.

Same here. Neglecting the possibility that the gun was bumped//jarred, perhaps it is a powder sensitivity issue? I use H4895, and it doesn't change much from 1000 degree days in CA to the teen's of the Wyoming late fall.

[smoothy8500]

100yd zero isn't far enough to see a big difference with temp and/or altitude variation. at 300yds and beyond is where I see my dope change.

[ShaunBrady]

If you have a solver that reports drop from the bore centerline in addition to come up, it's pretty easy to see that air density doesn't affect the 100 yard zero significantly. With velocity, even 100 fps might not be a full click. That insensitivity is one of the stronger arguments for 100 zeros.

Barrel time effects could be larger, but it's hard to imagine they'd give the 3 mils at 400 yards reported 15 years ago.

If it's a sporter weight barrel and wood stock that uses a pressure pad at the front of the stock, free floating the barrel and bedding the action would be the first thing I tried to fix that zero shift. No pressure pad at the front of the stock and random contact along the barrel channel would be even worse.