MacD, you are trumpeting the call of any true engineer - let's test some more! I will be testing with 16", 18", 24", and 26" barrels with the .223. We can see if any clues come out of that data. One of the bigger challenges is how many tests you have to run to get a high confidence in your data. I've loaded over 100 rounds for this test so far and I'm only doing 2 shots per test point.

Lets keep in mind there is temperature sensitivity and temperature stability !!!
All powders are affected by ambient temperatures. Some powders more so than others. When the temps dip there will be a velocity drop, how much and at what temperature depends on the powder itself. This is why it's recommended that you record temperature and humidity with load development. It's also the reason I develop my loads around the season they'll be used.
Some powders tend to lose it's consistency (extreme spread widens) as well when temps drop. I've often wondered if this isn't just a poor choice of components more so than anything.

Quote::

These limited test do not prove muzzle velocities don't rise with barrel temperature rise.

Ambient temperature and humidity plays a role !!!
I can assure you that pressure can/will raise with increased barrel temperatures.
Do the same tests with your .270........

Chambered, after firing 40 shots in the. 223 and 6.8 and not getting any rise in velocity, I decided not to subject the throat of my. 270 to such abuse. I found out what I wanted, that two shots from a cold barrel isn't going to affect the velocity significantly for the 2nd shot due to any rise in barrel temperature. After 2 shots from my .270, the barrel temperature starts to soar! Plus the most shots I have had to take in any hunting situation with the .270 has been three.

I have finished loading up the ammo for the temperature sensitivity range session - a total of 116 rounds including a few FMJ factory rounds as a reference/control. The plan is to fire rounds with powder temperatures near 20F and 95F depending on how well temperature can be controlled. Firing will switch between several .223 rifles, an 18" ARP, a 20" ARP for the 130gr Sierra GameKings, and a .270 Win Tikka T3 Lite at intervals to let the barrels cool back down to ambient. It will likely be 30 days before results will be available.

40 .223 Rem
52 6.8mm SPC
24 .270 Win
116 Total

I'm trying to find a thermometer to measure the powder temperature with. Maybe with a probe I can install in a case with powder. Any ideas.




Loads are:

.223 Rem (CCI 400)
55 FMJ, S&B (factory)
40 V-Max, 26.0gr 1200R
40 V-Max, 26.0gr AA2200
64 BPB, 25.0gr Varget
64 BPB, 26.0gr CFE223
64 BPB, 24.0gr TAC
64 BPB, 23.0gr 8208 XBR


6.8mm SPC (CCI450)
110 FMJ, S&B (factory)
90 HP, 29.5gr Re7
95 TTSX, 30.0gr AA2200
100 AB, 31.0gr 1200r
110 BTHP, 28.6gr AA2200
110 BTHP, 28.6gr AA2200 (CCI 400)
120 SST, 27.0gr Re10x
130 SGK, 32.5gr LeveRevolution
130 SGK, 29.0gr H335
130 SGK, 33.0gr CFE223
130 SGK, 33.0gr CFE223 (CCI 400)
130 SGK, 29.5gr TAC
130 SGK, 30.5gr Varget
130 SGK, 29.0gr 8208 XBR

.270 Win (CCI 200)
100 SPP, 56.0gr CFE223
130 SGK, 46.0gr Varget
130 SGK, 45.0gr 8208 XBR
130 TSX, 56.0gr IMR4350
130 TSX, 56.0gr IMR4350 (Rem Magnum)
140 AB, 62.0gr MagPro (Rem Magnum)

Did a test run using a crockpot with water to heat up the bullets. On "keep warm" it heats to 120 degrees F. I can let it cool down to 100F, then start shooting bullets for hot powder temperatures. Temperature is measured very accurately with the digital thermometer used for taking temperature under the tongue.

For the cold part, I have a freezer temp gauge but it so inexpensive, I question its accuracy. I thought I'd look into something I could use while shooting and hunting like a Kestrel wind gauge. However, the units that have temperature and humidity, get pretty pricey.

Anyone have any experience these these type of devices that you can share?

www.midwayusa.com/prod...uctFinding

I’ve been working with different thermometers trying to develop the processes for controlling hot and cold powder temperatures. With over 100 test rounds to fire, I cannot afford to get to the range and have surprises or unknowns. As mentioned before, I have found a crockpot filled with water set on “keep warm” can be used to achieve cartridge temperatures in the 95 to 100F range. The crockpot will heat the water (and submerged cartridges) to 120F and cool-down will place the rounds in the needed temp range. An IR temperature “gun” will be used to determine when the water is in-range and then a digital oral thermometer will measure the exact reading. An oral mercury thermometer will be a back-up. The oral thermometers have been accurate within 0.5 degrees but have a limited range between 86 and 106F.

Keeping the cartridges below 30 F has been more of a challenge. Finding a solution has turned this into a science experiment. The winter weather has given me time and opportunity to work things out. Yestereday, we were hit with the 3rd winter storm of week. With 2" of snow and ice on the road combined with Texans that don't know how to drive on the icy pavement and the roadways turn into a mess. Freezing rain hit us overnight so it’s a skating rink today. Since I was stranded at home 3 days this week, I started playing with ways to measure powder temperature and how it changes over time. I found a cooking meat thermometer that has been accurate within 1 degrees using the melting snow and ice outside to calibrate it. I tried installing the probe tip inside a .270 Win case full of powder (see picture below). I used masking tape to increase the probes diameter to fit in the case neck and then secured it with tape around the outside of the case neck.

I initially took two sets of temperatures readings with a step change from freezer cold (0F) to indoor ambient (67F), then indoor ambient to outdoor ambient (25F). I wasn’t expecting the results shown below. Powder temperature changes very rapidly toward the ambient temperature. I noticed variations in temperature change rate if I touched the probe or case on the first freezer to room temperature (note the line has some irregularities) so did a second run with the expose probe shaft insulated. That made a difference on how fast the powder charge warmed up. Then I thought it would be good to see how the rate of change was altered if I held the case in my hand. Wow!! Looks like I’m going to have to wear fleece gloves to handle the cold cases and maybe load as many into magazines as I can so the cases aren't touched. Still, I’m going to have to get the rounds in the chamber and fired within a couple of seconds after they have been removed from their temperature environment. I found it doesn’t take much more than 30 minutes for a case to reach ambient and you can see from the graph its essentially there in about 10 minutes.

The chart above is about what I would expect to see in the absoption and radiation of heat with a heat range as listed. Remember that brass is a fair conductor of heet - just slightly lower than aluminum - so the transfer rate has to be expected to be fairly quick. The mass is low (comparitavely) so it takes a very small exchange of calories to affect the cartridge.
Direct sunlight will heat the cartridges quickly even in low temperatures due to the IR radiation that doesn't effect the air temperature but will quicly effect any absorptive material.

Florists use a water absorbing foam type block for some flower arrangements. If you got a block of this and put holes in it with a dud round so the live ones just fit, you could freeze the block for cold and put hot water in for warm and keep the cartridges in the block until ready to load them. If you use really hot water you could try a chambering a few rounds and then waiting say 30 seconds, eject and measure the temperature drop. Same for cold ones. Just a thought.

To avoid touching the cold rounds and upsetting the temps, you could dispense with the magazine and fire single shot loading, or dropping, each round into the chamber with a pair of tweezers. With the magazine fitted, you should only have to drop the round onto the top of the magazine and it should chamber OK using the bolt.

Thanks for the ideas. Keep them coming. I'm actually thinking it would be better to have the rounds preloaded in the magazines. I can label the bottoms. I can use some dense foam that fits the top of the cooler and cut out a slot to hold the magazines upside down with the bullets in the cold medium (like a pelican case). That way I wouldn't have to touch the rounds. The foam would also help prevent warmup when I opened the cooler top to pull a magazine out. Don't have enough magazines for the .270 though. This may be a good excuse to ....

Your biggest problem is going to be chambering the round in a rifle that will be at ambient (and likely different) temperature. If it's 70F outside and your attempting to test 0F rounds, those rounds are going to warm up very, very quickly once chambered. Likely too quickly to give you very accurate results.

IMO, It's an uphill battle attempting to test temperature sensitivity of powders unless the firearm is exposed to the same temps at which the powder is being tested.

But it can still be a fun exercise as any excuse to shoot is a good one.

Azar, That's why I say this is turning into a science project. The challenges are not simple. I have a large cooler which I will fill with ice and cold soak the rifles in. Will be interesting to see how the scopes do. I may put some back-up sights on some of the rifles. At least I should be able to get the barrels down near freezing with the cooler. Rounds will be in the chamber less than 5 seconds so I think I have the challenge contained. I will use spare rounds to increase barrel temp so its warm (100 F). This morning I altered my approach to the cooling and heating process. I'm going to insulate the magazines and make them little "coolers" so my hands don't touch the cases and they can be cycled through the action in a few seconds after their removal from the cooler (cold) or crock pot (warm). The cold rounds should be within 3 degress of their starting temperature.

Cool.

Sounds like you are covering your bases. It will be neat to see your findings.