WST and Temperature Sensitivity

[Hank Ellis]

Here and on other boards, the issue of temperature sensitivity of certain powders has come up. Some claim wide variations and others claim very little variation. Asking locally didn't bring a good answer so I had to find out for myself.

The question: Is Winchester Super Target powder sensitive to temperature?

The test: Chrono a series of loads with the only variables being powder charge and temperature.

Each of the loads was made on the same day from the same canister of powder, the same box of primers and the same box of projectiles.

Brass: Winchester.

Primer: Winchester Large Pistol.

Powder: Winchester Super Target

Projectile: GAT 230 gr LRN

Charge: 4.1, 4.2, and 4.3 gr

OAL: 1.260

Crimp Dia: .470

Gun: Springfield Armory 1911-A1 Loaded in .45ACP 5" barrel

Springs: 12.5 lb ISMI recoil with one .090 Hiett shock buffer, 17 lb ISMI main

Weighed 20 projectiles randomly selected (meaning I grabbed a handful from the box). The lightest weighed 234.8 gr and heaviest weighed 236.1 gr. Average weight was 235.3 gr. Loaded 100 rounds each of the three charges. Each charge was then divided into three groups. One group was placed on ice in a cooler for three hours. The second group was placed in my range bag. The third was placed in a cardboard box and set on the front seat of my car for three hours.

Chrono procedures were three shots per string for six strings for each of the nine loads. Free air temperature was mid-80s F. with about equal humidity. Results are as follows.

Average Velocity fps

4.1 gr Hot 731.3

4.1 gr Norm 743.4

4.1 gr Cold 737.3

4.2 gr Hot 742.3

4.2 gr Norm 750.8

4.2 gr Cold 749.2

4.3 gr Hot 759.7

4.3 gr Norm 763.0

4.3 gr Cold 759.9

Average Power Factor USPSA

4.1 gr Hot 172.1

4.1 gr Norm 174.9

4.1 gr Cold 173.5

4.2 gr Hot 174.7

4.2 gr Norm 176.7

4.2 gr Cold 176.3

4.3 gr Hot 178.8

4.3 gr Norm 179.5

4.3 gr Cold 178.8

The answer: My conclusion is that unless you are cutting the power factor real close, don't worry excessively about temperature of the cartridge affecting power. It would be prudent however to do a similar temperature test prior to going to a major match. I do find it interesting that the 'hot' and 'cold' rounds were both slower than the ambient temperature loads.

Yes, I'm aware that even at 4.1 that my loads are still exceeding the USPSA power factor by a too large a margin. I want to tweak the crimp diameter a bit tighter and do another test with loads from 4.0 to 4.2. More work is in the future.

Thoughts and comments invited.

[Guest Larry Cazes]

When I first starting loading with WST for my 40 limited setup, I did a similiar experiment and came to the conclusion that WST is NOT temp sensitive enough to make a significant difference in Chrono results. A few questions to ponder.....

- what is the specification for accuracy for the chronograph you are using?

- What order were the tests performed in? Hot, cold norm, etc?

- was the barrel cleaned in between any tests? How many rounds were fired for each string?

The drop off in velocity at both Hot and Cold is curious and I am interested if it can be attributed to an independant factor not stated in your message.

Great data and thanks for posting it.....It re-enforces my choice of WST. It is my favorite powder for both .40 and .45.

[Hank Ellis]

- what is the specification for accuracy for the chronograph you are using?

- What order were the tests performed in? Hot, cold norm, etc?

- was the barrel cleaned in between any tests? How many rounds were fired for each string?

The chrono was a Pact MK IV. Accuracy spec? Good question. Anyone have an answer?

The tests were done in the order of Normal, Cold, then Hot.

The barrel wasn't cleaned at all during these tests. I was looking for 'real world' results. Meaning what would these loads do in my gun during it's normal state of semi grubbyness. Each load was fired in a 3 round string for 6 strings. I used a 3 round string as that is the procedure for chrono for USPSA matches.

The Hot and Cold dropoff is puzzling. Anyone have any ideas as to why?

I'll revisit this thread when I do the second batch with 4.0 through 4.2.

[gm iprod]

Without knowing the Standard Deviations and Extreme Spreads an accurate conclusion about temperature sensitivity is not possible. As the differences could be well within the likely range of any particular load.

I have found that WST when loaded to near maximum pressures will sometimes do strange things when subjected to large temperature variations. But seeing as it gets very humid here as it gets hotter I would not like to say that the humidity was not more or less of a factor. I can't test for this. Looking at the variations in PF in your data I would say that you are safe even if the temperature gets hot. (By your standards of hot and cold)

[kevin c]

Without knowing the Standard Deviations and Extreme Spreads an accurate conclusion about temperature sensitivity is not possible. As the differences could be well within the likely range of any particular load.

How about the fact that I find (with an entirely different load/powder from the one under discussion) the first shot of 8 out of 10 chrono'd strings will have the first shot out of the barrel be the lowest velocity of the string? My conclusion is that the powder I am using (VV320) is temp sensitive in the load I am using. What other conclusions might be reasonable? I thought about physical barrel changes with heating, but then figured that, if it were a factor, it would be the same with all powders as consecutive shots were fired, and also would render the whole issue moot.

Am I over or misinterpreting my data?

[.40AET]

Kevin- I get the same results as you with N320. First shot is 20fps slower than the next 9. As long as the 9 out of 10 make major, I decided to stop losing sleep trying to figure out why. Maybe the bullets move faster in a warm barrel???

[kurtm]

Yep I have noticed this with N320 also. I think it has more to do with the manualy chambered first round as appossed to the semi auto chambered round. In other words how the powder was " shook" in the case. I tried this once. I fired the pistol one time and then set it in a craddle with the barrel horizontal, just like you would be holding it if shooting. I let the gun sit in the shade for about 10 minutes, so it wouldnt get a sun load, and then put 10 shots over the chrono. There was very little deviation between shots, an no indication of the "slow" first round. I have noted this when firing groups. Most pistols will put the manually chambered round just slightly out of the "functioned " group. From now on I shoot a "stettling" shot and go from there! KURT

[MoNsTeR]

With a sample size of 3 for each test, any conclusions you could draw would scarcely qualify as "tentative". Shoot 30 of each and get back to us

[Hank Ellis]

Shoot 30 of each and get back to us

OK it's not 30 but how about 18.

It appears I didn't make myself clear on my procedures. So instead of trying to describe it in words, I put up a copy of the spreadsheet results up for y'all to look at.

Sure a 5 shot string would be a more precise indicator of what the load performance is, but you don't get 5 at a USPSA chrono. You get 3. So 3 it is.

Took a look at the first shot data and found that about half of the first shots were slow also. Interesting. Don't know why and really don't care. What I do care is those 3 shots being enough to make the desired power factor. Especially if I grab a box of cartridges that's been sitting in the car all morning.

I'm not real happy with the SD of any of the loads. We'll see soon after the next trip to the chrono.

[Tree Rat]

Fire a round over the chrono turning the barrel to the sky and again turning the barrel to the gorund before firng each shot.

You might be amazed at the velocity disparity EVERYTIME. While temp sensitivity is an issue all it's own. This sounds more like case position sensitivity for the propellant.

When I chrono, I always fire the first round outside the chrono to normalize the string. If chrono'ed at a match, you might offer up four rounds and ask that they fire that first in the same manner.

BTW, the temp test appears to indicate that WST is inverse temp sensitive (decreasing velocity with increasing tempurature).....something I have experienced as well.

Try the position test and decide.

TR

[Les Snyder]

If my memory is correct, and who knows these days, Win Super Target (WST) replaced Win 452AA which was very temperature sensitive as Tree Rat has suggested .... the velocity decreased with an increase in temp.... down here 452AA would drop 100fps if the temp got above 90F... that was a real shame as it was the most accurate .45acp load I ever shot.... WW231 really dropped when the temp dropped... when WST arrived, while there may be some variations with temp, it was nothing like those that had preceded it, and nothing that I ever worried about at the chronograph.... never tried to get that close to the power factor... even at 175.... still think that WST is the best all around propellant for handguns.... regards

[Hank Ellis]

Here we are with the second batch of loads. The variables that changed from the first batch is the powder charge and the free air temperature. Temps were in the low 90's F.

Average velocity fps

4.0 Hot 723.2

4.0 Normal 716.3

4.0 Cold 717.8

4.1 Hot 731.4

4.1 Normal 733.9

4.1 Cold 729.9

4.2 Hot 746.4

4.2 Normal 742.9

4.2 Cold 745.9

Average power factor USPSA

4.0 Hot 170.4

4.0 Normal 168.8

4.0 Cold 169.1

4.1 Hot 172.3

4.1 Normal 172.9

4.1 Cold 172.0

4.2 Hot 175.9

4.2 Normal 175.0

4.2 Cold 175.7

Comparing the two batches it appears that, ignoring other factors, the temperature of WST doesn't significantly affect chrono results.

Someone could spend a lifetime pondering loads and pouring over chrono results. I have no desire to do that. All I wanted to know is WST temp sensitive and what will work in my gun at my local ranges. Now I can quit shooting my 180 PF loads, load up several 1000 of 4.0, and get to the job of getting A hits.

[Tree Rat]

I agree this data set shows little disparity and I'm sure others have seen the same results, but I'm telling you.........Your going to get Chrono'ed at a match later this year and that 4.0 load is going to break your heart.

Good Luck.

TR

[DogmaDog]

Hmmm. My major load in .45 w/230gr LRN is 3.9 gr WST

It has always averaged around 169/170 PF for me. Course, I haven't done a whole lot of tests.

Hank, thanks for asking the question, designing a test, and getting the answer! Well done! I think we can be confident in your results.

DogmaDog

[Hank Ellis]

Your going to get Chrono'ed at a match later this year and that 4.0 load is going to break your heart.

Another local shooter did some tests recently with the same projectile and powder combination using three different guns. He came up with 4.1 making 168 pf. Stirring brain cells together we figured that differences in individual chronos, atmospheric conditions, or dozens of other variables make going to 4.0 just too risky from a match pf standpoint. For now 4.1 it is.

Hmmm. My major load in .45 w/230gr LRN is 3.9 gr WST

Dogma, I didn't run 3.9 over my screens but I can tell you that it would not make major in my gun over my chrono. At 4.0 normal there was one string that went 164.6 pf and another at 166.7. The others were in the high 169 to mid 170 range. Another reason for going to 4.1, don't need the stress of worrying whether I'll pass the test.

[Stician]

An oldie but a good one. Been looking for the answer how WST reacts to varying temp.