PRS/NRL22 ammo in sub 45 degrees

[IamJoHo]

So I keep reading that under 50 degrees and Center-X/Midas+ start to shit the bed and I think I was seeing that 2 weeks ago especially 50yrds and farther. I could see the bullet dropping differently in the scope.

I have a match this Saturday where the high will be 43 and the following Saturday is showing a high of 37. It will definitely be close to freezing or below at the start of the match.

I'm wondering if anyone keeps their ammo in something like a small Styrofoam cooler with maybe a couple hand warmers inside or something like this. I have some small medical coolers and was thinking of throwing a few boxes in it and then keeping the mags inside my pocket after loading.

Thoughts? Oh and I have checked around and can't find any Lapua Polar Biathlon.

 

[littlepod]

I load my magazine, and stick it in my pocket so it's near my body and stays at a non freezing temp. I regularly shoot in the 40's and never had problems with ammo shitting the bed.

Or if you want to let the ammo get cold / ambient temperature, then do it, and chrono it.

 

[IamJoHo]

I load my magazine, and stick it in my pocket so it's near my body and stays at a non freezing temp. I regularly shoot in the 40's and never had problems with ammo shitting the bed.

Or if you want to let the ammo get cold / ambient temperature, then do it, and chrono it.

Yeah I will be trying that at bare minimum. I also need to get a chrono. Another expense to add to this whole endeavor.

 

[littlepod]

Yeah I will be trying that at bare minimum. I also need to get a chrono. Another expense to add to this whole endeavor.

Borrow someone and just start jotting down how ammo performs. I haven't chrono'd in months.

The other thing you can do is is true your MV at the match, depending if you can get zero time or not... Basically get your ammo to the temp you think you're going to shoot that day, shoot a group at 200 yards, and true your MV to what it took to get to 200.

 

[drglock]

I keep my mag in my pocket with a Hothands hand warmer and I keep three boxes in a compartment in my shooting pack with several Hothands packets in with them. You’ll be amazed at how warm they’ll keep the boxes of ammo.

 

[1911Shootist]

Minnesotan here... Sometimes it's the 40's, sometimes 30's or 20's, but it seems most start to fall apart somewhere in there.

I typically don't worry about it in the 40's. Matches colder than ~30F, I'll try to keep my ammo warm. Ammo boxes, and mags in a pocket/muff with a handwarmer. It does seem to help at times, but not always. Several pounds of steel will suck the heat out of a few grams of brass and lead in a hurry.

 

[IamJoHo]

What about barrel warmers. Is that even a thing?

 

[1911Shootist]

Not that I've seen. I'd worry about differential heating unless you can wrap the entire circumference.

Running quick and dirty numbers for electric heat:
18" barrel, 0.9" diam, 30F delta

18" = 0.457 m
30 ΔF = 16.7 ΔK
A = 3.14 * 0.9" * 18" = 50.9 in^2 = 0.033 m^2

q = -λΔT/Δx
q = [-(50.2 W/(m*K)) * 16.7 K] / 0.457 m
q = 1834 W/m^2

P = q * A
P = 1834 W/m^2 * 0.033 m^2
P = 60 W

Getting 60 W of heat into an 18" barrel will be challenging with battery power. Most 12V heat trace is 3-5 W/ft, so there'd be too many wires to get around the barrel with off the shelf tape. Anything hotter could be a safety concern.

Battery capacity would also be an issue... 60W / 12V = 5A... If it's a short 4 hour match, that's 20 Ah needed, which would be at least the size of a large motorcycle battery and ~10 lbs if going LiFePO4 (and ~$400).

 

[IamJoHo]

Not that I've seen. I'd worry about differential heating unless you can wrap the entire circumference.

Running quick and dirty numbers for electric heat:
18" barrel, 0.9" diam, 30F delta

18" = 0.457 m
30 ΔF = 16.7 ΔK
A = 3.14 * 0.9" * 18" = 50.9 in^2 = 0.033 m^2

q = -λΔT/Δx
q = [-(50.2 W/(m*K)) * 16.7 K] / 0.457 m
q = 1834 W/m^2

P = q * A
P = 1834 W/m^2 * 0.033 m^2
P = 60 W

Getting 60 W of heat into an 18" barrel will be challenging with battery power. Most 12V heat trace is 3-5 W/ft, so there'd be too many wires to get around the barrel with off the shelf tape. Anything hotter could be a safety concern.

Battery capacity would also be an issue... 60W / 12V = 5A... If it's a short 4 hour match, that's 20 Ah needed, which would be at least the size of a large motorcycle battery and ~10 lbs if going LiFePO4 (and ~$400).

Damn man. You really dug into that one quick. I dont know if any of that math is even real. Way beyond me.

 

[DairyDictator]

Not that I've seen. I'd worry about differential heating unless you can wrap the entire circumference.

Running quick and dirty numbers for electric heat:
18" barrel, 0.9" diam, 30F delta

18" = 0.457 m
30 ΔF = 16.7 ΔK
A = 3.14 * 0.9" * 18" = 50.9 in^2 = 0.033 m^2

q = -λΔT/Δx
q = [-(50.2 W/(m*K)) * 16.7 K] / 0.457 m
q = 1834 W/m^2

P = q * A
P = 1834 W/m^2 * 0.033 m^2
P = 60 W

Getting 60 W of heat into an 18" barrel will be challenging with battery power. Most 12V heat trace is 3-5 W/ft, so there'd be too many wires to get around the barrel with off the shelf tape. Anything hotter could be a safety concern.

Battery capacity would also be an issue... 60W / 12V = 5A... If it's a short 4 hour match, that's 20 Ah needed, which would be at least the size of a large motorcycle battery and ~10 lbs if going LiFePO4 (and ~$400).

Thermodynamics is a bitch....

 

[Jefe's Dope]

We were shooting sub 45* on Sunday and I wasn't having issues with Midas. We were shooting golf balls at 205 and an "egg yolk" steel at the same. Some KYLs out to 150 yards as well.

 

[1911Shootist]

Yeah it doesn't seem to matter until you get to <30F for most.