Barnes Ammo - Extreme temperature sensitivity with VOR-TX?

[CleanShot]

Hello

I'm just getting started out with reloading so in the meantime I picked up some Barnes VOR-TX factory ammo in 7RM 150gr TTSX. It's been unseasonably warm in the Northeast and so I have been mostly shooting in quite warm weather say mid-60s or above. Yesterday however the temps dropped down. Still warm by our standards for end of November but down to the upper 30s or lower 40s. I noticed my shots were hitting rather high so I had to go down a few tenth a of a mil. Before I go off blaming my turrets slipping from not being tightened enough, I thought I'd ask if anyone has a similar experience this here I am.

Anyone seen this with Barnes factory ammo?

Thanks!

 

[CleanShot]

Any ideas? I should mention AP app thought I should be at .5 mil up and really I was shooting only .3 up.

 

[Bravo 4]

If going from hot to cold I would think the opposite would occur, hitting lower not higher. That would be for both ambient and ammo temps. Run the numbers in your ballistic calculator again and change the temps. Also during those weather changes there will probably be changes in station pressure that would need to be noted and input as well to get a real solution to your problem. Other info would help as well; zero range and distance shooting, have you previously shot and confirmed DOPE, do you know your true muzzle velocity or just going off what the box said, how well does your rifle group that load, have you checked the adjustments in the scope, parallax adjusted for, did you change rests (zero off bipod- shooting off the side of a deer stand)...just off the top of my head, I can go on but you get the point. There are several variables not mentioned.

Having said that and not knowing any particulars, I just punched some numbers into my app. 150 TTSX @2950 assuming a 200 yard zero and with a .5 mil adjustment you are shooting 300 yards or less.
Went from:28.5 hg/65 degrees at 300 yards= .6 mil drop
To: 31.5 hg/30 degrees at 300 yards= .65 mil drop
Those are some big changes in temp and pressure, from good to bad for bullet flight and only a .05 mil change.
Even if you punch in those numbers and put 2900fps (for shooting in the lower temp and higher pressure) to account for a big change in lower powder (ammo) temp change it still only makes it .68 mils.

If you are anywhere near these conditions and hitting .2 mils high then I would suspect it to be something else. Like I said, it should go the other way around anyways...you should be hitting lower. I suspect it's something else. Also remember with the apps its "crap in= crap out"!

 

[Bravo 4]

Buy the way, Remington loads the Barnes ammo. I know a guy who is a supervisor at the ammo plant. He said they have been on a big Barnes kick, he said as far as he knows Remington only uses Alliant powders. Which powder for which load he cannot say. However I'm sure you could do a little work and find their best powders for whatever cartridge/bullet and research those powders for temp sensitivity. When all else fails google it.
I usually try that first.

 

[CleanShot]

I was thinking I need to come up more for colder weather as well but the ballistics calc also was down .1 so instead of the regular .6 is hows it showed me .5. Could have been the other conditions? I was at a 300 yard range (the longest in my area) and I'm zero'd at 200 yards. I'm shooting a 7RM.