RL 22 Temperature sensitivity test

I have always heard how temperature sensitive RL 22 is and I have had some bad experiences with RL 25 that I assumed was due to temperature sensitivity. So for a long time now I have sworn off RL powders with the exception of RL 15 that I use in my 375 h&h and 416 rem. But alas there was a problem in hodgdonville I could not get the velocity out of my 375 ultra that I wanted with any other powder. So I broke down and loaded up some rounds with some RL 22 I had laying around. And as expected I got 2900 ish fps with a 300gr TSX and excellent accuracy with no pressure signs. But this gun is destined for the bush veldt and big bad Cape Buffalo or may be a Brown bear or big bull Elk. So with that in mind and looking at a possible 50 degree temperature change during a day hunting I wanted to know just how bad the velocity swing would be form hot to cold. A call to my favorite tech support from my favorite bullet maker got a guess of 120 fps loss for a 50 deg temp change so if at 85 deg its going 2900 and at 35 deg its going around 2780 ( yes the animal may not know the difference but I will and more importantly the gun might with a poi change). I just had to know so I did a little experiment. I loaded up 3 sets of 3 rounds with IMR 7828ssc, VV N 165 and RL 22, and for good measure I threw in a few more calibers and powders, these included a 338 rum with H1000, 300 rum with Retumbo a 270 wsm with Magpro and a 6.5X55 with H4350. To do the test I put 3 rounds from each gun / powder combo in a zip lock bag and then put them in the freezer in a small ice chest full of ice. I let them set in the freezer for a day or so and then went to the range. I got to the range and it was a 48 deg that day so I had a set of ammo left out to reach ambient temp and then put a set of ammo on my defrost in my truck and keep it running on high. I had a Fluk temperature gauge the infrared kind to masseur the temperature of each set of ammo and the gun barrel. My plan was to shoot the cold ammo then the ambient ammo and finally the hot ammo one after the other so by the time I got to the hot ammo the gun should be smoking hot. I wanted to get the gun as cold as I could so I rubbed ice on the outside of the barrel ( in this kind of weather this sucked) once that was done I measured the temp of the barrel at 33 deg and the cold ammo at 5 deg, the ambient ammo was 49 deg and the hot ammo was 125 deg. I then shot each gun and powder combo in order, cold ( with cooling down the barrel with ice), ambient and then hot with the barrel now smoking hot.

The results, all velocity was recorded with a 35P and is a average of 3 shots for each temperature.
(As per usually with me I have missed placed my print out so this is some what from memory!!)

Also all the ammo had Barnes TSX except the 6.5 witch was Nosler partitions

RL 22 had 20 fps form cold to hot 2890 to 2910.
Imr 7828ssc had about 40 fps from cold to hot at 2800 to 2840
VV N 165 had about the same form 2780 to 2835

All the other powders and guns had about 40 to 50 fps spread with 6.5x55 and H 4350 being the worst at 60 fps this was a surprise for me as this is an extreme powder.
One other strange thing was Retumbo and the 300 rum Lost velocity with the hot ammo form 3350 ( this is what this load always runs ) to 3290 for the hot ammo???.

I wish I had my print out for this day but I have looked every were for it and can not find it.

I then wanted to just test the RL 22 and the 375 rum so I did the test again with 2 sets of 6 rounds each.
This time it would be the most extreme swing of 5 deg to 125 deg.
The results were about the same with a 12 fps change!!!!!!!!

The hot rounds The cold rounds
2918 + 2894 +
2874 – 2854 -
0044 E 0040 E
2891 M 2879 M
0016 S 0013 S

I realize that I did not really prove any thing statistically but this does make me feel better about using RL 22 in my 375 rum. Next is to do the same thing with my 257 Roy and 264 win to see how much bore diameter may play in this. I do think that each gun also may vary with each powder so the problem may be more complex than just temperature.

I cant wait for the weather to warm up so I can get out in the garage and play some more.



So For the 375 rum RL 22 looks like the powder! Now I just hope that the new lot I buy to load all the ammo I want will be the same!??!?!?

Your test is interesting. I think results would be a bit diff. if fired in summer temps. I think it's pretty hard to get your ammo "hot" in the truck. I have seen pretty good temp. swings (up to 75-80fps) using some powders in some cartridges on 90deg+ days vs 35deg days. I suspect bore diameter & case volumn play into it a bit. This summer I'll have to play w/ this some as 7828 is my favorite power in several calibers, just seems a bit more consistent than RL22 for me.

The ammo in the truck was 125 deg via the Fluke temp gun. And it was shot strait from the truck to the gun! I acutaly tured down the heat cause it got up to 135 deg and I thought that was way to hot!

Prdator, Well done and well thought out. This is an important issue and you will hunt with greater confidence as the result. Thanks for sharing your efforts.

Good post! I appreciate the work done here. However, if I had done this experiment I would have based it on the lot to lot variations RL powders have been known to suffer. All said and done, GOOD JOB!

PRDATOR,

I got alittle chance to test R22 temp stability as well this weekend.

I compared R22 and H4831 in a 7RM.

My shooting was done Friday morning while temps were in the low 30s. These are loads that I worked up before last years hunting season while temps were in the 80s. POI was not effected much, at least not enough to matter in a hunting situation.

My R22 loads went over the chrono from 45-60 fps slower than they did prior to hunting season and the H4831 loads went over the chrono 70-80 fps slower. I was really surprised that the Hodgdon powder showed more temp sensitivity than the alliant powder. I would have thought it to be the other way around.

That was just a one time test that doesn't prove anything but, I did find it quite interesting.

By the way, the R22 groups opened up a bit to around 1"(previously .5) and the H4831 groups stayed tight like they were a few months back despite the velocity difference.

Reloader

I have hunted with RL-22 from the Selous of Tanzania in Africa at 95 degrees to Colorado and Alaska at 20 below with my .358 STA and saw no noticable difference in performance or POI. Good shooting.