freezing my reloads for MV testing?

[punkwood2k]

I need to test my reloads for MV variance between temperatures.. My comeups are different enough between 72F and 100F, that I need to Chrono my rounds through a couple different temps, preferably on the same day at identical ranges.. Would putting one set of rounds in a cooler under ice packs (with thermometer) work for simulating MV in winter? Has anyone tried this? I figure if I shoot one set at freezing, and one set at ambient (around 80F), that would give me enough data to interpolate the comeups at different temps?

Any ideas / advice?

Thanks!

 

[stoopy]

Dry ice. Maybe cool the barrel of the gun with dry ice also. Shoot the cold rounds first to see if the barrel heating up changes things also.

 

[ultrarunner7]

Uh. It will for the powder but the ambient air the bullet is flying in(being warmer) will produce different results man.

Cold air is much "heavier" than warm air. Example: When you open your freezer, you could feel the cold air just rush downward towards the floor. Cold air in the atmosphere behaves the same way and this is why it stays separate from air that is warmer. Why is cold air heavier than warm air? Cold air is denser than warm air. The molecules are packed closer together. Since the warm, humid air is less dense, the bullet travels through it with less friction. So, while freezing your loads will test burn rate at a given temp, it won't give you dope for it. Just wait and shoot in it

 

[Assault116]

Uh. It will for the powder but the ambient air the bullet is flying in(being warmer) will produce different results man.

Cold air is much "heavier" than warm air. Example: When you open your freezer, you could feel the cold air just rush downward towards the floor. Cold air in the atmosphere behaves the same way and this is why it stays separate from air that is warmer. Why is cold air heavier than warm air? Cold air is denser than warm air. The molecules are packed closer together. Since the warm, humid air is less dense, the bullet travels through it with less friction. So, while freezing your loads will test burn rate at a given temp, it won't give you dope for it. Just wait and shoot in it

yeah but he should still be able to get relatively valid muzzle velocities from it, Everything down range will be invalid as ultrarunner has pointed out, but for MV differences @ specific temps, it should get you quite close as far as data to enter into a ballistics app.


The tough part is going to be keeping it consistent from shot to shot, barrel temp will quickly start to raise the temp in the cartridge if left in the chamber very long. You'd literally have to yank a round directly from the cooler, chamber it and fire it as quickly as possible and do that consistently throughout the string. If you load them all in a mag and start cycling through them, the temp will be changing the whole time, and with rapid fire, obviously it will be exaggerated by the heat of the chamber itself. Also the amount of time each one is in your booger hooks, that's going to warm them up as well.

 

[ultrarunner7]

Absolutely.

Sent from my XT1080 using Tapatalk

 

[DocB]

PW,

Just be careful about condensation on the ammo. It can really raise the pressures.

HTH,
DocB

 

[Victor N TN]

Shoot now. Shoot again in January. You can try different things. But it won't be the same.

 

[redbullitt]

I would think that would yield good chrono data to see how the powder behaves! Everything else can be accounted for later as long as you know what the powder is doing. Definitely not a good source for DOPE, but it could be useful for powder selection.

1 shot at a time, let chamber etc cool.

I'd be curious to see some powder comparisons using that method. Best bet would be to shoot from right by your freezer. Take the round out, crank it through the chronograph.

Varget is supposed to be consistent, so that makes sense you did not see much. Maybe try some h110 out of a pistol or some w748 or Reloder and see if they turn out different results.

 

[Skyking]

Make sure you use a temp stable powder.

Using Temperature Stable Powder - YouTube

 

[Fred_C_Dobbs]

It will work to the extent that the cooler charges will produce a lower MV. But the temperature of your barrel also will have some influence. But I doubt it plays a big a role as charge temp does.

I have a varmint rifle load using a temp-sensitive powder that I worked up in the winter that shoots bugholes. But when the weather turns warm, the groups blossom. So I chronoed them, and found they'd gone from ~4000 to ~4200 fps, which had moved me off my 'accuracy node.' Also gave me a pretty stiff bolt lift.

I don't varmint hunt much in the summer, so it wasn't worth the effort to me to work up a reduced charge weight load for the heat, but I still like to poke holes in paper with that rifle in the summer. So I left the box 'o bullets in the fridge overnight, then carried them to the range in a lunch-sized cooler with a couple of blocks of blue ice. And it brought my MV and my group sizes down right back where I wanted them, no more than 10 or 12 fps from what they'd clocked in the cold.

I'd reckon the cartridges were no more than 50°F when I shot them. I'd pull one round out at the last moment, wipe off the condensation with a bandana, chamber it, and light it off as quickly as I was able, so's it wouldn't heat up sitting in the chamber. I wasn't worried about internal condensation because smokeless powder is very hydrophyllic. It loves to suck up humidity from the air. And the charge itself displaces all but a tiny volume of air from the case. I'm fair certain it would suck what little air was still trapped inside as dry as a bone within a day or two of being loaded. Not to mention, my refrigerated bullets shot great.