RL-26 Temperature Drift Data

[Engineering101]

I've seen quite a few guys getting interested in RL-26. The discussion also seems to get to temperature drift at some point with some guys saying they will give up 100 feet per second and stick with Retumbo since RL-26 has "some" velocity/pressure shift with temperature.

I've got a real world sample of 1 where I measured that drift using 162 ELD-Xs in my Brux 7mm WSM. Alliant says the drift is 0.5 feet per second per degree F. In my rifle the drift was twice that. I fired three shots at 200 yards that grouped 0.906" with an average velocity of 3,039 fps in 18 degree F weather. I came back another day when it was 38 degrees F with 5 rounds of the same load to verify that this group would repeat. The 5 shots went into 1.563" (4 of those into 1"). The average velocity of this bunch was 3,061 fps. So a 20 degree F increase in temperature produced a 22 fps increase in velocity. So there you go. One data point.

 

[brentc]

I've seen quite a few guys getting interested in RL-26. The discussion also seems to get to temperature drift at some point with some guys saying they will give up 100 feet per second and stick with Retumbo since RL-26 has "some" velocity/pressure shift with temperature.

I've got a real world sample of 1 where I measured that drift using 162 ELD-Xs in my Brux 7mm WSM. Alliant says the drift is 0.5 feet per second per degree F. In my rifle the drift was twice that. I fired three shots at 200 yards that grouped 0.906" with an average velocity of 3,039 fps in 18 degree F weather. I came back another day when it was 38 degrees F with 5 rounds of the same load to verify that this group would repeat. The 5 shots went into 1.563" (4 of those into 1"). The average velocity of this bunch was 3,061 fps. So a 20 degree F increase in temperature produced a 22 fps increase in velocity. So there you go. One data point.

Thanks. What chrono did you use?

 

[tbrice23]

Thanks. What chrono did you use?

Also, what per cent case fill do you have, 105% , 80% , 50%.....???
Some folks find case density effects the temperament .

 

[Engineering101]

Chrono used was a CED Millenium II which is very reliable. I've used it for years and it is rock solid (if you set it up using a laser bore sight like I do so it is always dead perfect).

Case fill is about 95% with 65 gr RL-26. It rattles but barely.

A little more info. I'm using Fed 215s with COAL at 2.935" which in this rifle amounts to 0.007" jump. Barrel is a 26.375" long Brux in a varmit taper mounted on a Savage model 114 long action.

 

[Garycrow]

3 shots one day then 5 on another with different lighting conditions over an optical chronograph isn't enough to draw the conclusion you're making. It's not enough data to substantiate your point. If you'd shot 25 shots each day it might have some statistical validity, but that's far too few shots to prove anything.

 

[Engineering101]

Garycrow

The lighting conditions were the same both days but you are right it is a small sample and I agree that it doesn't prove anything. It is just one example of what might happen if you use RL-26 in different temperatures.

 

[J E Custom]

Garycrow

The lighting conditions were the same both days but you are right it is a small sample and I agree that it doesn't prove anything. It is just one example of what might happen if you use RL-26 in different temperatures.

+1

I have found the increase in velocity to be much more than 0.5 ft/sec per degree also. Mainly because of the higher temperatures we get in the south. The increase really started to grow at 70o+ and increased even more when it neared 100o or more.

The solution has been to carry the ammo in a small cooler wrapped in a towel and with a freezer pack to maintain Powder temperature around 45 to 50 degrees.

J E CUSTOM

 

[codyadams]

I have done some testing at 20°, but it was with a rather cheap optical chrono. I would like to know what it's doing, so I can at least put the velocity to temp change in my ballistics app. The velocity node I found is rather large, so I think it would take a large temp swing to cause me to loose accuracy

 

[Greyfox]

I have been very interested in giving R26 a try in my 6.5x284 given the increase in reported velocities. My current velocity is 2975FPS. For me, temperature stability is an important consideration since my hunting for the last several years consists of spending October in Wyoming at 45-75F temperatures at 4500Ft, and November in Canada at 0-45F at 2300Ft. My load over this time period has been 58gr Retumbo@+95% case fill. This load has held its zero at both locations(as well as my NE home state at 350FT and 30-75F). Also, for several seasons, my drops using my G7 RF/BC have been proven to 1000+ yards with test shots and game taken in Wyoming and Canada. Based on my experience, Retumbo has proven to be very temperature stable. I will note that I have used the same lot of Retumbo and Fed210M primers over this period. As has been suggested, I am also very skeptical when I see tests using chronograph data, frozen bullets, limited shots, etc. I'm very interested to hear of any actual field use tests of R26. Currently, the information available is sketchy and my past experience with the Reloader series has been quite poor when it comes to temperature stability. Hopefully R26 changes this.

 

[Engineering101]

Greyfox

A couple comments. First - were I you I would stay with Retumbo if you have it working good. RL-26 will drift. Alliant who imports the stuff from Nitrochemie says so. As I indicated I think they have understated the drift at 0.5 fps per degree F. Speaking of drift, Alliant now has 3 flavors/families of powder. One flavor has horrible temp drift - namely RL-22/RL-25, one flavor has moderate drift which is the Nitrochemie stuff which includes RL-26 and RL-33 and one flavor is rock solid stable which is the Bofors stuff like RL-16 and RL-23. I'm guessing your bad experiences in the past were with the RL-22 type powders.

Secondly, over several years, I have shot several thousand high power rounds over my CED chrono. I record all data and keep all targets. The same loads produce the same velocities time after time day after day (if temps aren't too different) so the chrono does not introduce much variability - maybe 10 fps. As I said you have to make sure alignment in pitch and yaw are perfect or it will read slow. The point is that if you know what you are doing you can get very consistent results from a good chrono. Unfortunately there are very few brands that I would recommend as good so a lot of guys question "chrono" results for good reason.

 

[Greyfox]

Greyfox

A couple comments. First - were I you I would stay with Retumbo if you have it working good. RL-26 will drift. Alliant who imports the stuff from Nitrochemie says so. As I indicated I think they have understated the drift at 0.5 fps per degree F. Speaking of drift, Alliant now has 3 flavors/families of powder. One flavor has horrible temp drift - namely RL-22/RL-25, one flavor has moderate drift which is the Nitrochemie stuff which includes RL-26 and RL-33 and one flavor is rock solid stable which is the Bofors stuff like RL-16 and RL-23. I'm guessing your bad experiences in the past were with the RL-22 type powders.

Secondly, over several years, I have shot several thousand high power rounds over my CED chrono. I record all data and keep all targets. The same loads produce the same velocities time after time day after day (if temps aren't too different) so the chrono does not introduce much variability - maybe 10 fps. As I said you have to make sure alignment in pitch and yaw are perfect or it will read slow. The point is that if you know what you are doing you can get very consistent results from a good chrono. Unfortunately there are very few brands that I would recommend as good so a lot of guys question "chrono" results for good reason.

Thanks For the useful info Engineering101. I do plan on sticking with Retumbo for this rifle. Why burn up the barrel with load work given my success through 800 rounds. I was more interested in a newer 6.5x284 rifle I have been working on but I'll likely stay with Retumbo on this rifle as well.
I haven't been so successful, with mixed results with my optical chronographs, but find the Lab Radar to be very promising.

 

[J E Custom]

In very cold climates, the primer needs to be hot enough to ignite the powder consistently especially powders with a slow burn rate in order to get good consistent ignition. It normally does not cause hang fires but it will mess with velocity and SDs.

Also Case capacities over 90 grains will normally benefit from the use of mag primers.

Hang fires/miss fires are normally caused by bad/contaminated powder as discussed.



J E CUSTOM

 

[codyadams]

I have a question related to this that I would like some different perspectives on. I am experimenting with RL-26 in my .260 AI, and my charges are around 49-50 grains with heavy for caliber bullets, and I am currently using CCI BR-2 primers. I have seen other people using this powder in smaller capacity (6.5 creedmore, 6.5x284 and .243) cartridges, and so what I would like to discuss is the use of magnum primers in these smaller cases with this powder and heavy bullets. What does everyone think the possible benefits/cons would be in this combo? My use ranges from around 0° up to 80°-90°.

 

[WildRose]

I have been very interested in giving R26 a try in my 6.5x284 given the increase in reported velocities. My current velocity is 2975FPS. For me, temperature stability is an important consideration since my hunting for the last several years consists of spending October in Wyoming at 45-75F temperatures at 4500Ft, and November in Canada at 0-45F at 2300Ft. My load over this time period has been 58gr Retumbo@+95% case fill. This load has held its zero at both locations(as well as my NE home state at 350FT and 30-75F). Also, for several seasons, my drops using my G7 RF/BC have been proven to 1000+ yards with test shots and game taken in Wyoming and Canada. Based on my experience, Retumbo has proven to be very temperature stable. I will note that I have used the same lot of Retumbo and Fed210M primers over this period. As has been suggested, I am also very skeptical when I see tests using chronograph data, frozen bullets, limited shots, etc. I'm very interested to hear of any actual field use tests of R26. Currently, the information available is sketchy and my past experience with the Reloader series has been quite poor when it comes to temperature stability. Hopefully R26 changes this.

RL26 is good but you might find yourself even happier with RL23 which is supposed to be more stable by design; literally. RL26 offers higher velocities but I shoot year round and our temps here vary by over 100 degrees through the year so stability is important to me.

I loaded up six rounds each going up in half grain increments to see where I'd start showing pressure signs in my .260's using ELD-X's, Accubond LR's, and Peregrine 125gr VRG4's. Even when I got up to some heavily compressed loads neither showed any signs of pressure. I did five loads of each RL19, 23, and 26 along with H1000.

Unfortunately my Chronograph died and I haven't had a chance to replace it yet but the accuracy was good throughout and I did hit at least one very good accuracy node with each of them.

RL 23 and 26 are pretty low in density so they fill up a case really quick. Even with the lighter loads I tried the powder was well up into the base of the neck.

I really expected I'd pressure out pretty quickly but it just didn't happen and it was pretty warm today, in the low seventies.

Unfortunately the wind was steady at 20 plus MPH all afternoon and very gusty so I'm going to have to find a calmer day to really figure out where I'm hitting my best accuracy nodes.

Unfortunately there's not a whole lot of load data available for 23 and 26 so I was having to wing it. I was very nervous about trying this but with the great reports I keep seeing on these two powders along with the fact they are readily available I felt it was worth the risk to see for myself.