CFE Temperature Test

[pds]

The issue of the temperature sensitivity of CFE powder has been brought up several
times on this forum. I decided to run the following test. I loaded 10 rounds of AA
cases with 31.0gr. of CFE powder, Rem 7 1/2 primers, and 123gr. Nosler CCBT bullets.
I loaded 5 of these in a magazine and put them in my freezer for about 8 hours. I
then packed the magazine between two packs of frozen blue ice then wrapped them in
two towels before heading to the range. Once at the range I placed the other 5 rounds in the front seat of my car for about an hour with windows rolled up in the sun. Outside temp was upper 70's. The gun used is a PF Grendel upper with a 22" Bartlein barrel.
When everything was set up I shot the 'cold' rounds first. I would guess that they were well below 32 degrees as I noticed that there was frost forming on the bullets as I loaded the magazine in the rifle. All 5 rounds were fired within less than one minute. I then shot the 'hot' rounds which I estimate to be at a temp of 85-90 degrees.
The velocity results using a Magnetospeed:

Cold Rounds
1-2442 fps
2-2510 fps
3-2490 fps
4-2480 fps
5-2485 fps
Min=2442 fps, Max=2510 fps
Avg=2481 fps
ES=68 fps
SD=24.7

Hot Rounds
1-2553 fps
2-2565 fps
3-2565 fps
4-2553 fps
5-2552 fps
Min=2552 fps, Max=2565 fps
Avg=2557 fps
ES=13 fps
SD=6.7

While the sample size is small, but with a difference of 76 fps average velocity between cold and hot rounds it appears that CFE is a temperature sensitive powder.
I hope this is useful info for everyone.

pds

[mongoosesnipe]

I plan to do some testing with ar comp once I work up a load from everything I have read it is increadably stable in 223 and 308 so I figure its worth a shot in the Grendel

[Michael]

pds - was there a difference in the grouping of the cold vs hot rounds? Know you mentioned 1MOA for cold, but was the POI different? I know the magneto speed will impact groupings, so do the 'cold' rounds group better for you without the chony on?

[pds]

pds - was there a difference in the grouping of the cold vs hot rounds? Know you mentioned 1MOA for cold, but was the POI different? I know the magneto speed will impact groupings, so do the 'cold' rounds group better for you without the chony on?

Michael,
I was shooting at 100 yds into 10-15mph quarter value head wind that was constantly switching from left to right. The cold rounds were all fired within less than a minute so small group size was not a concern. However I just went and measured both groups the cold rounds measure 1.4" moa with 4 shots in a .908" moa group. The hot rounds measure 1.6" moa with 4 shots in a 1.10" moa group. The 4 shot cold group is about 1/2" lower POI than the 4 shot hot group. I feel the magnetospeed has an effect on both POI and group size.
Hope this answers your question.

pds

[JASmith]

It looks like the degree of sensitivity is about average. Hodgdon published charts for the 30-06 here: http://www.hodgdon.com/smokeless/extreme/page2.php#top

[LR1955]

PDS:

I guess it depends on how someone defines 'temperature sensitive'. To me, your results indicate a powder / primer combination that is normal. Nothing extreme at all.

I did something more extreme with the various types of issued 7.62 and got about 70 fps difference. That with powders specifically designed to be consistent over a wide range of temperatures.

BTW, if you ran your test under more normal temperature ranges, you would find the differences to be extremely small. Small enough that you would have to start testing with different primers and neck tensions to weed out variances.

LR1955

[dammitman]

Now thats really good testing. I for one appreciate your post with information. Thanks! Just one question. Whats your COAL using those nosler 123 bullets? I have some and am getting poor results.

[Michael]

Michael,
I was shooting at 100 yds into 10-15mph quarter value head wind that was constantly switching from left to right. The cold rounds were all fired within less than a minute so small group size was not a concern. However I just went and measured both groups the cold rounds measure 1.4" moa with 4 shots in a .908" moa group. The hot rounds measure 1.6" moa with 4 shots in a 1.10" moa group. The 4 shot cold group is about 1/2" lower POI than the 4 shot hot group. I feel the magnetospeed has an effect on both POI and group size.
Hope this answers your question.

pds

It does, thank you. All things being equal, I would guess that 1/2" drop at the temps you were working with is not too horrible until you get out beyond about 300yds. Still in the kill zone for hunting purposes (hypothetically). I would be curious as to the grouping size and difference in POI without the magneto speed...maybe something for me to play with later...

[pds]

Now thats really good testing. I for one appreciate your post with information. Thanks! Just one question. Whats your COAL using those nosler 123 bullets? I have some and am getting poor results.

d'man,
The COAL for this test was 2.205" which in this chamber seats the 123NCC bullet about .010" off from touching any part of the throat.

pds

[explorecaves]

PDS:

I guess it depends on how someone defines 'temperature sensitive'. To me, your results indicate a powder / primer combination that is normal. Nothing extreme at all.

I did something more extreme with the various types of issued 7.62 and got about 70 fps difference. That with powders specifically designed to be consistent over a wide range of temperatures.

BTW, if you ran your test under more normal temperature ranges, you would find the differences to be extremely small. Small enough that you would have to start testing with different primers and neck tensions to weed out variances.

LR1955

I was thinking the same thing....