RL33 Temperature Regression Thread

[barnesuser28]

I have a little data to contribute.
Rifle: 30/375 S.I. 215 berger seated .040 off the lands, 85 grains of RL33 in weight sorted brass. Velocities taken with magnetospeed V2

Temp 73* F
Velocity. 2970 2997 2967 AVG 2978 fps

Temp 84* F
Velocity. 2994 2985 2986 2990 AVG 2988 fps

Difference in velocity = 10 fps
Difference in temp = 11* F

.91 fps difference per degree of change. I know this isnt a large difference in temp, so the results may not be extremely precise, but it is something. I will test again this summer once it hits 95*F+

 

[jmden]

That second shot in the first string at the lower 73F temp seems abnormally high. If that shot was similar to the other two, that would drop your average from that temp even more, seeming to show that, with your loading in that rifle, RL33 is quite temp sensitive.

Are those temps you mention with the ammo AND rifle at that ambient temp for each shot?

Have you tried seating closer to the lands? If I recall, some have seemed to find less temp sensitivity with RL33 when bullets were seated very close to or in the lands. I'd be curious to see what would happen if you could duplicate those loads mentioned above in the same temps with the bullets much closer to the lands.

 

[barnesuser28]

The ammo and rifle were the same temperature. I have not tried seating closer to the lands, as this load shoots an average of .25 MOA. The cold bore shot is usually around 1" high at 100 yards so i am going to be testing different methods on getting that cold bore shot where it should be, so i should be able to test it again around the same temp.

 

[Pdvdh]

If I recall, some have seemed to find less temp sensitivity with RL33 when bullets were seated very close to or in the lands.

What I recall reading is that Kirby Allen and others were finding that seating bullets close to the lands with RL-33 powder resulted in notably lower ES. I don't recall any correlation to MV involving both variables; seating depth AND temperature sensitivity.

The idea of testing the affect that two velocity affecting variables (temperature and seating depth), have on MV with any particular powder seems pretty abstract for these reasons: 1) varying bullet seating depth will alter MV with temperature held constant, and 2) temperature change will alter MV with seating depth held constant. So I have to question how a guy would be able to distinguish between the competing affects on MV of one variable from the other - seating depth or temperature.

Similar, but not quite the same as the conundrum with the common Thermos... It keeps hot things hot. It keeps cold things cold. How do it know???

 

[jmden]

What I recall reading is that Kirby Allen and others were finding that seating bullets close to the lands with RL-33 powder resulted in notably lower ES. I don't recall any correlation to MV involving both variables; seating depth AND temperature sensitivity.

The idea of testing the affect that two velocity affecting variables (temperature and seating depth), have on MV with any particular powder seems pretty abstract for these reasons: 1) varying bullet seating depth will alter MV with temperature held constant, and 2) temperature change will alter MV with seating depth held constant. So I have to question how a guy would be able to distinguish between the competing affects on MV of one variable from the other - seating depth or temperature.

Similar, but not quite the same as the conundrum with the common Thermos... It keeps hot things hot. It keeps cold things cold. How do it know???

I think you're right, phorwath. I mistook temp stability for low ES.

I continue to see some folks say RL33 is temps stable and some say it's not. Wish there was a variable we could pull out of our hats to explain this.

 

[Pdvdh]

Folks are certainly reporting impressive MVs with heavy for caliber bullets from their magnum capacity cartridges with RL-33. I secured a 1 lb container, but haven't yet produced any ammo. I'm looking forward to trying it. I'll find a use for it even if it is a little temperature sensitive. My ballistics program can compensate for MV change with temperatures. But at some point, enough change in MV will negatively affect accuracy and POI.

 

[steeltraps]

I have been very impressed will RL-33 in my 338 Lapua imp. . I wish i could find a 5 or 8lb can of it! I would settel for a 1lbs. Im getting 3025 fps with 105 grs of RL-33 with 300 otm berger and 215 mag. primers. I have .370 neck 0 freebore chamber and 28 in MTU bartlein barrel. I all ways right down ever shoot i fire from ever gun. The sensity of RL-33 doesnt seam that bad to me. I have only shot gun from 50 degrees to 80 degrees so far. I am getting 1 fps in crease in velocity for every 2 degrees in temperature. Im using both magneto speed and PVM-21 chronographs. My 10 shot es for my RL-33 load is 12fps, so i concider my finding to be accurate in MY gun.

 

[barnesuser28]

jmden, retested at 74* today
2965 2970 2972
Avg 2969

2988 - 2969 = 19 fps over a 10* difference. 1.9 fps per degree change. Thats quite a bit. This load is 4 grains under max, i think that loads that are close to max pressure will have a smaller swing in velocity from temp.

 

[steeltraps]

jmden, retested at 74* today
2965 2970 2972
Avg 2969

2988 - 2969 = 19 fps over a 10* difference. 1.9 fps per degree change. Thats quite a bit. This load is 4 grains under max, i think that loads that are close to max pressure will have a smaller swing in velocity from temp.

Your are correct, they will. I once took a 284 load to a match, it got unseasonally hot that match and the last string of 20. From rounds 14 to 20 i almost had to beat the bolt open! This is NOT good for the gun= or what i intended. I didnt know it was going to happen like that, but i shot the Highest score ever with those high pressure 284 because of low ES.

 

[barnesuser28]

Also, i think primers may have an effect on velocity, my guess is the priming compound is also temperature sensitive. I am using fed210 M primers in my tests.

 

[barnesuser28]

Im stumped, i froze some ammo and shot them today, powder temp was 33 degrees, avg muzzle velocity over 5 shots was 2964 fps. That brings it down to .48 fps per degree change.

 

[Jud96]

Im stumped, i froze some ammo and shot them today, powder temp was 33 degrees, avg muzzle velocity over 5 shots was 2964 fps. That brings it down to .48 fps per degree change.

It may be more effected by warmer temperatures than colder ones.

 

[jmden]

Im stumped, i froze some ammo and shot them today, powder temp was 33 degrees, avg muzzle velocity over 5 shots was 2964 fps. That brings it down to .48 fps per degree change.

But...that may take us back to post 26.

 

[elkaholic]

Good thread Mark! I just wish I had enough RL33 to test I did shoot some in my 30/375 S.I. with 230 Bergers and reached 3178'. I also shot some in my 6.5 SS with pretty amazing results. I reached 3238' with the 150 Matrix but started seeing extractor marks. The only thing of note, as far as this thread goes, is that I noticed in two consecutive days shooting over my mag speed that jumping the bullets a long ways (around.060"-.070") increased pressure considerably over seating them close to lands. i.e. a load seated .010" off lands took two grains less, for the same velocity, as a load seated .070" off. Granted, this was one small test, but seemed rather significant.......Rich