RL33 Temperature Regression Thread

[Max Heat]

What kind of chrony are you using? I would bet your weird velocity stem therein.

It's an optical "shooting chrony" brand basic F1 model. It could have been the cause of the anomaly (is that spelled right?). Especially considering that the 1st shot did produce an error.

And 33 doesn't like bullet jump? With an overbore 7RUM, you NEED to have some, to keep the pressure from spiking.

I'm backing off on this thread now, as the OP probably thinks that I'm hell-bent on throwing it off course. He WAS pretty specific about the topic. Since 33 is what I am running now, I'm definitely interested in hearing what others have to say regarding it's possible temperature quirkiness. But judging by the responses so far, there doesn't seem to be enough info out there yet, due to it still being so fresh on the market. I'm hungry for ANY data & observations regarding this new powder.

Primer-blowing pressure spikes caused by LOW temps is unsettling. I really hope it turns out NOT to be the case, once a sufficient amount of data comes in. I've blown a couple of primers with [overly] hot loads of 22, in hot weather. But NEVER with 33 (or even 25, for that matter).

 

[MontanaRifleman]

Did some more testing last Friday and here are the results

6-284, 105 Hybrid targets over 60 gr RL33, 26" 5C Broughton (low pressure load)
Cold rounds were cold soaked in my freezer @ 5*. Then I transported them in a small cooler with an ice pack from the freezer. Temp in the cooler remained about 20* for about an hour prior to shooting, Warm loads were loaded at room temp of 70* then placed on floor of vehichle by the floor heater. The floor area remained about 80-85 for about 1 hr prior to shooting.

5 shots of each were fired

Cold rounds, 20*.... 3302, 3302, 3282, 3293, 3295.. Avg, 3295
Warm rounds, 80*.. 3322, 3311, 3313, 3304, 3302.. Avg 3310
Avg fps/degree diff, 0.25 fps/degree

Fairly consistent with the first test of this load.

Also tried the 6.5 WSM, 160 Matrix over 65.5 gr of RL33, 27" 5C Broughton barrel. Results were squirrely. The rifle was show pressure issues similar to previous when originally working up loads with my nitrded barrels.

Cold rounds, 20*....3084, 3132, 3119... Avg, 3112
Warm rounds, 80*..3134, 3097, 3099, 3113...Avg, 3111

Essentially no apparent affect. Like I said, the rifle was showing signs of weird pressure. This load was about 2 gr less than the original max working load I dtermined from ladder pressure testing. Cold rounds produced a medium heavy bolt lift and ejector marks. Warm rounds did not. I then proceeded to shoot some accuracy test rounds from 66 to 64.5. After firing 6 total rounds to get zeroed in with various charges of 65.5, 66, 65 and 6.45. I blew a primer with the 64.5 load, got the case stuck in the chamber and called it a day. All rounds showed pressure signs of heavy bolt lift and ejector marks. Ambient temp was 45.

Bottom line, I would not put a lot of faith in temp regression test with the 6.5 WSM rounds.

Results from the 6-284 are looking good. Still hope to do more testing and looking for anyone else who might have useful data to share.

 

[bassin93]

I load 103grns of RL33 behind the 300SMK in my edge. In the summer at temps around 80 to 90 my velocity is avg of 2996 and that is with a 7fps spread.
This winter with temps in the low 30s my velocity is running avg 2945 with a 15fps spread.
I have been shooting this powder for about a year now and like it because of the increased velocity I get out of it and the low spreads esp in the summer months and just deal with the difference due to temp

It also works very well in my 284 Rank, 4 fps spread and that is summer temps, haven't run it over my chronograph in the cold

 

[MontanaRifleman]

I load 103grns of RL33 behind the 300SMK in my edge. In the summer at temps around 80 to 90 my velocity is avg of 2996 and that is with a 7fps spread.
This winter with temps in the low 30s my velocity is running avg 2945 with a 15fps spread.
I have been shooting this powder for about a year now and like it because of the increased velocity I get out of it and the low spreads esp in the summer months and just deal with the difference due to temp

It also works very well in my 284 Rank, 4 fps spread and that is summer temps, haven't run it over my chronograph in the cold

Thanks for the input Bassin. It looks like you are seeing about 1 fps per degree of temp.

 

[5280yotes]

I picked up a couple of pounds of R33 and hope to get a consistent load out of my 27inch brux and some 180 hybrid bergers.

 

[brentc]

I found 1/2 MOA load for 180vlds that runs 3140 fps with comfortable pressure in Winchester brass in my 7RM 28" bbl.

 

[steeltraps]

Im getting 3/8 moa from 100 to 1300 yards with RL-33 in 338 lapua imp. with 28 inch bartlein barrel. 3025 fps average. Tight neck . 0 free bore. 105 gr of RL-33 , 5 th from rifling. My 10 shot ES was 13 with fireform loads and 10 fps with 1x lapua. Just like MontanaRifleman i experemented with temp. I put my rounds in refrigotor though. Tested with heat gun 40 degrees to 80 degrees, the inside of my truck rounds and found little difference in sensitivity! Actually the only diff i saw was the 80 degree rounds had 2fps ES over 10 shots. The average stayed at 3020 Fps. I have Neco PVM-21 chronograph so i fell that RL-33 in my expericane is very good for where i hunt in alabama. I may try putting some rounds in our deep frezze and chronoing them just for fun

 

[5280yotes]

I found 1/2 MOA load for 180vlds that runs 3140 fps with comfortable pressure in Winchester brass in my 7RM 28" bbl.

Wow!! That's impressive. Where did your loads start and where did you finish up at.

 

[brentc]

Wow!! That's impressive. Where did your loads start and where did you finish up at.

I started at 75.0 and pushed up to 78.5 showing ejector wipe. My first sign of pressure was a slight shadow on some of my cases at 77.5 grains. My load finished out at 77.0 grains. My initial load testing was done at 110 yards from a bipod with 4 shots printing a .6 MOA group. I then verified drops at 525 with a 2" five shot group on my steel target and then I followed them up with two center of mass hits on milk jugs at 535. I'll probably take it on my bear hunt in a couple weeks to see how it does.

 

[deadidarren]

would that be heavily compressed .

 

[brentc]

would that be heavily compressed .

Lightly compressed. I actually had loads up to 79.5 grains that were quite compressed but didn't shoot them due to pressure signs showing up sooner.

 

[jmden]

There has been talk of RL33 perhaps showing less temp sensitivity with minimum bullet jump. Do a search or two on this site as there was a really good thread or two that seemed to show this fairly prominently. And, many have found this powder to be very temp insensitive in their load/rifle and others just the opposite. What's the difference? One aspect could be seating depth. Other aspects could come from the variables we may be inadvertently introducing to our testing as mentioned below possibly resulting in worthless or next to worthless data. Food for thought...

I've come to realize lately that having your ammo at a certain temp and your gun at a certain much different temp (how often does that happen when hunting anyway?) potentially introduces all kinds of variables when checking velocity to the point that the data may be irrelevant. What we may need to do is have both ammo and rifle at the same ambient temp and test in warm and then in cold ambient temps. Otherwise, with expansion and contraction of bore and bullets in different temps we may just be producing worthless data as bore and bullet dimensions change in different temps. If you've got a warm bore (possibly small amount of expansion) and a cold bullet (possibly small amount of contraction compared to what to it would be if it was at the same warmer temp the bore is at), we may be causing pressure differences simply based on the physics of metal contraction/expansion that messes with the pressures in the bore and the resultant velocity creating useless data. Guys blowing primers in cold temps or just seeing higher velocities at cold temps, the latter of which is apparently not unusual, could simply be from a slightly contracted/smaller bore due to cold temps. That'll raise pressure fast. Some barrel metals/alloys may be more affected by temps than others? I don't know, I just think that instead of trying to isolate the variable of powder temp by warming or cooling ammo (something I'd done for years), we are actually increasing the variables in the system and in an artificial, arbitrary manner likely resulting in bad data.

I understand the idea of trying test what the powder does in different temps, but that's just one variable in the entire system and trying to isolate that may not be realistic or give usable data. This was hashed out on another site lately and I had my ideas about this changed.

Shoot at ambient cold and hot with rounds and rifle at same temps (as would most likely be the case in a hunting situation) and see what happens. It may not be as convenient as simply putting rounds in a cooler, but I believe the resulting data will likely be more accurate and realistic and perhaps actually show what the entire system is doing.

Not sure I've done a good job of trying to explain this. If so, I apologize.

 

[SHRTSHTR]

There has been talk of RL33 perhaps showing less temp sensitivity with minimum bullet jump. Do a search or two on this site as there was a really good thread or two that seemed to show this fairly prominently. And, many have found this powder to be very temp insensitive in their load/rifle and others just the opposite. What's the difference? One aspect could be seating depth. Other aspects could come from the variables we may be inadvertently introducing to our testing as mentioned below possibly resulting in worthless or next to worthless data. Food for thought...

I've come to realize lately that having your ammo at a certain temp and your gun at a certain much different temp (how often does that happen when hunting anyway?) potentially introduces all kinds of variables when checking velocity to the point that the data may be irrelevant. What we may need to do is have both ammo and rifle at the same ambient temp and test in warm and then in cold ambient temps. Otherwise, with expansion and contraction of bore and bullets in different temps we may just be producing worthless data as bore and bullet dimensions change in different temps. If you've got a warm bore (possibly small amount of expansion) and a cold bullet (possibly small amount of contraction compared to what to it would be if it was at the same warmer temp the bore is at), we may be causing pressure differences simply based on the physics of metal contraction/expansion that messes with the pressures in the bore and the resultant velocity creating useless data. Guys blowing primers in cold temps or just seeing higher velocities at cold temps, the latter of which is apparently not unusual, could simply be from a slightly contracted/smaller bore due to cold temps. That'll raise pressure fast. Some barrel metals/alloys may be more affected by temps than others? I don't know, I just think that instead of trying to isolate the variable of powder temp by warming or cooling ammo (something I'd done for years), we are actually increasing the variables in the system and in an artificial, arbitrary manner likely resulting in bad data.

I understand the idea of trying test what the powder does in different temps, but that's just one variable in the entire system and trying to isolate that may not be realistic or give usable data. This was hashed out on another site lately and I had my ideas about this changed.

Shoot at ambient cold and hot with rounds and rifle at same temps (as would most likely be the case in a hunting situation) and see what happens. It may not be as convenient as simply putting rounds in a cooler, but I believe the resulting data will likely be more accurate and realistic and perhaps actually show what the entire system is doing.

Not sure I've done a good job of trying to explain this. If so, I apologize.

jmden, makes sense to me We are finding that RL33 is pretty stable in our LRKM Terminator or our 338LAI. 25fps is about average with these rifles and a 50f. degree ES. Something I think we can live with. Time will tell as we move into the summer and our testing will be with rifles at ambient temps.

Ray

 

[steeltraps]

I see your point as well. I have though about puttung the whole gun, 338 lapua in the deep freeze and trying to shoot it after it got cold. The nightforce scope would fog up, but i could shoot it , with the magneto speed chrono i use for field work on. Do you think this would closer mimic frezzing mornings in north alabama? I see how ambient temp. plays into the sensitity of the load. If i sight in gun at 50/67/29.13 then i right it down= fps =3010 fps .Then i may shoot this gun=load again at 30/67/29.13 i also right that fps down= 2995 fps. So i would come to the conclusion that 30 degrees colder = 15 fps slower. To me its an easy fix. I always carry my kestel 4500 and my ballistic program in my range=hunting bag with my Vector 4 rangefinder. I get what Jmden is saying about metal expanding and contracting. What do you guy think about me doing a WHOLE gun deep freeze then shoot deal? Then what about putting the rifle in the truck on the dash of the winsheald and testing it? I have a 300 yard range that is with-in feet of my yard and deep freeze. Do you guys feel this would be a better test of RL-33 temp. sensitivity?