RE 17 temp sensitivity?

[archerross]

This powder has been gaining some popularity over the past year. I am curious to know if anyone can speak about temperature sensitivity of RE 17. My gunsmith friend just gave me some firsthand indication that it may have some sensitivity issues. He found, when running it near max pressures, nearly 50 fps jump in ave. velocity when going from 55 to 85 F. Has anyone had similar results? Do you think temp sensitivity would be as much of an issue if you are running below max?

 

[kombayotch]

I found it to change about 0.8 fps/ deg. F

It was not as stable as Varget in my 308 Win. loads.

 

[Steve Blair]

The 6BR loads I developed at 85f had no significant velocity increase at 100f. Quickload indicates approximately 58 ksi, velocities confirmed by chronograph.

Although temperatures do not vary as much in San Diego as elsewhere, this winter will provide the best indicator.

Archeross: What was the temperature range and approximate pressure?

 

[archerross]

sleepygator: Temps were 55F and 85F. I don't know the pressures. I can tell you he was shooting 6.5x47 Lapua with the charge just under max.

kombayotch: Over what range in temperatures did you see the 0.8 fps/deg change? I am load developing in weather that will likely be up to 30 degrees warmer than when I'll be elk hunting. I know Varget is quite stable, but I am getting better velocities with slower powders in my 6.5-284.

 

[watercam]

In my 6XC w/ 115 DTACs I had to drop from 40 gr. to 38.5 gr. when I used loads developed at 60 deg. were shot at close to 80 deg.. Accuracy was still good but I lost a bit over 100 fps. velocity.

 

[jlmurphy]

It was my understanding that the Reliant rifle powders were all double based, giving higher energies, but were more temp sensitive. I use Re22 in my .243 varmint rifle, I appreciate the extra velocity, and at the varmint shoots I can adjust the elevation for each relay, for more precise shooting I use H4831.

 

[Steve Blair]

My 6BR load is 32.5 behind a Sierra 107 MK. It is not a max load, maybe around 53 ksi. Perhaps temperature sensitivity increases at higher combustion temperatures near max pressure.

I have also noticed less temp sensitivity when using moly coated bullets. The lower starting force probably reduces the pressure curve peak.

 

[kombayotch]

kombayotch: Over what range in temperatures did you see the 0.8 fps/deg change? I am load developing in weather that will likely be up to 30 degrees warmer than when I'll be elk hunting. I know Varget is quite stable, but I am getting better velocities with slower powders in my 6.5-284.

Here is some test data for you,taken last night):

This is a 308 Win. with around 6600 rounds on the barrel. About 4k rounds ago, the 210M loads were performing the same as the CCI 250 are now. Same slope of 0.8 fps/F on the temperature change too. The barrel has worn a bit...

I'm sure RL-17 is more temperature stable at higher pressures. It isn't a great fit with 190s in the 308 Win. I believe it would be more stable with 210s, but I haven't tested any of my 210 loads.

For comparison, here is an IMR3031 load I also tested recently:

I have an RSI Pressure Trace system in case anyone is wondering where I got the pressure data.

 

[archerross]

kombayotch: You are my kind of shooter! I love seeing data like this! Am I correct in assuming that you obtained your extreme points of -10F and 160F by placing cartridges in the freezer and oven, respectively? It appears that RE 17 does push back the pressure curve, at least compared to IMR3031. Very interesting.

 

[kombayotch]

I used the freezer in the clubhouse and a small cooler with a heating pad in it and let the rounds soak for a couple hours. A thermometer was placed in each area.

Rounds were shot in a round robin sequence,room, cold, hot, room, cold, hot...) and the barrel was allowed to cool between each shot. Absolutely no time was spent trying to aim beyond making sure they went through the chronograph. You don't want to give them any time to change temperature in the chamber.

I wouldn't recommend going that high in temperature if you can't measure pressure. The relationship is linear, so after the first cold and room temperature shots, I can estimate where the high temperature one is going to be in pressure.

 

[Steve Blair]

Well, winter is not quite here but I obtained an additional data point Friday.

The attached load has performed very well in my Savage 12F 6BR. Shooting 10 October over the chrono, it averaged 2979.8 with 9.9/4.1 ES/SD. The temperature was 95 degrees (I live in San Diego). Yesterday, same load, same shooting range (even the same lane), temperature 55 degrees, it averaged 2866.7 with 73.7/29.1 ES/SD. That is a 113.1 fps difference and the variability is what I saw at much lower loads during development. I saw little change at 85f but the Kurzzeit chrono is not likely wrong. This is a difference of 2.8 fps per degree. An interesting aspect is the non-linearity. Note the temperatures that archerross reported in an earlier response.

Just another reason to pay attention when reloading. What if I had done it the other way around? In this instance 33.0 is not a top load, even at 100f. Henceforth, when citing a Reloder 17 load, I will note the temperature.