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WST Temperature Sensitivity


cheby
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I heard that WST powder is somewhat temperature sensitive. Does anyone have any data supporting that? I am about to start using this powder for my 40SW major loads and wonder how much I will need to adjust in July

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7 hours ago, cheby said:

So let’s say my ammo is 950 f/s at 50degree. How much would it slow down at 90?

Take 10 rounds of ammo put them out in the sun on a warm day, take 10 rounds, put them in a ziplock bag in your cooler with an ice pack, take 10 rounds and keep them at ambiant temp.   Shoot them over your chrono back to back.

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WST is not actually reverse temp sensitive.  It is hottest at mid temps and slows down when it is cold or really hot.  If your major is 172PF at 65-70 deg., you are safe a freezing and 95.  I can't find the curve right now, but the slopes are mild.  Same with minor at 132.

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26 minutes ago, zzt said:

WST is not actually reverse temp sensitive.  It is hottest at mid temps and slows down when it is cold or really hot.  If your major is 172PF at 65-70 deg., you are safe a freezing and 95.  I can't find the curve right now, but the slopes are mild.  Same with minor at 132.

 

I want to see the data on this. I also want to know how you achieved different AMMO temperatures while comparing velocities in "Hot, Cold, Medium" temps. I shot WST for years in 40 Major and during my AMMO tempreture testing WST was significantly faster at close to Freezing temps and significantly slower at Hot temps at or above 100 Degrees. 

 

Most people think that the powder/temp testing is associated with the ambient temperature which you are shooting in. The ambient temp has much less effect on the burn rate of the powder versus the temperature of the actual Ammo. The ammo temp is usually similar to the ambient temp because the ammo is usually exposed to the current ambient temp conditions. But if you artificially heat or cool ammo loaded with WST powder you will absolutely see a velocity difference that is inverse of the ammo temp. Hotter temp ammo = Slower velocity. Colder temp ammo = Faster velocity.

 

When I was shooting WST I would artificially heat the ammo to 110+ degrees then immediately chrono it to verify that it still made major PF velocity. You can artificially heat the ammo by simply letting it sit in the direct sun light, or just lay it over the heating vent in your vehicle.

 

For what its worth, my testing showed that 110+ degree Temp WST 40 cal Ammo making 165 - 166 PF was also 175 - 180 PF at Freezing temps. This all being shot out of a 5 inch KKM Barrels. If you are going to use WST make sure it still makes power factor when its 110+ degrees.

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4 minutes ago, CHA-LEE said:

 

I want to see the data on this. I also want to know how you achieved different AMMO temperatures while comparing velocities in "Hot, Cold, Medium" temps. I shot WST for years in 40 Major and during my AMMO tempreture testing WST was significantly faster at close to Freezing temps and significantly slower at Hot temps at or above 100 Degrees. 

 

Most people think that the powder/temp testing is associated with the ambient temperature which you are shooting in. The ambient temp has much less effect on the burn rate of the powder versus the temperature of the actual Ammo. The ammo temp is usually similar to the ambient temp because the ammo is usually exposed to the current ambient temp conditions. But if you artificially heat or cool ammo loaded with WST powder you will absolutely see a velocity difference that is inverse of the ammo temp. Hotter temp ammo = Slower velocity. Colder temp ammo = Faster velocity.

 

When I was shooting WST I would artificially heat the ammo to 110+ degrees then immediately chrono it to verify that it still made major PF velocity. You can artificially heat the ammo by simply letting it sit in the direct sun light, or just lay it over the heating vent in your vehicle.

 

For what its worth, my testing showed that 110+ degree Temp WST 40 cal Ammo making 165 - 166 PF was also 175 - 180 PF at Freezing temps. This all being shot out of a 5 inch KKM Barrels. If you are going to use WST make sure it still makes power factor when its 110+ degrees.

Thanks Charlie. That’s exactly what I was looking for 

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19 minutes ago, CHA-LEE said:

I shot WST for years in 40 Major and during my AMMO tempreture testing WST was significantly faster at close to Freezing temps and significantly slower at Hot temps at or above 100 Degrees. 

 

And it would have been faster yet if you chrono'd at 65.

 

I don't artificially heat or cool ammo.  I just chrono ambient temp.  I leave it out, let it col or heat to whatever ambient is, then chrono.  And why on earth are you shooting in 110 deg. weather?  That's insane.  You must be out West where there is zero humidity.  Oh, I see you are from CO.  Have no idea how WST varies from sea level to  a mile high.  I can say that at sea level +, what I presented was accurate with the 45 ACP bullseye loads I tested.

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14 hours ago, zzt said:

 

And it would have been faster yet if you chrono'd at 65.

 

I don't artificially heat or cool ammo.  I just chrono ambient temp.  I leave it out, let it col or heat to whatever ambient is, then chrono.  And why on earth are you shooting in 110 deg. weather?  That's insane.  You must be out West where there is zero humidity.  Oh, I see you are from CO.  Have no idea how WST varies from sea level to  a mile high.  I can say that at sea level +, what I presented was accurate with the 45 ACP bullseye loads I tested.

 

Do you measure the actual temperature of the ammo itself? or just assume that it achieves the same temp as ambient by leaving it out? Doing temperature testing without actually measuring the temperature of the ammo isn't very useful. Digital IR Style Temp gauges are fairly cheap these days. Get one and test this stuff with actual REAL data to leverage.

 

I also want to point out that, yes I have tested the velocity of WST ammo at varied "Middle" temps between 32 - 110 degrees and the velocity change tracked pretty consistently with the temp change.

 

Lastly, yes there are matches hosted in temps north of 110 degrees. More importantly, there are major matches with chrono stages were the staff leaves the ammo sitting in the sun so the ammo is HOT when you chrono it vs the ambient temp.

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36 minutes ago, CHA-LEE said:

 

Do you measure the actual temperature of the ammo itself? or just assume that it achieves the same temp as ambient by leaving it out? Doing temperature testing without actually measuring the temperature of the ammo isn't very useful. Digital IR Style Temp gauges are fairly cheap these days. Get one and test this stuff with actual REAL data to leverage.

 

I also want to point out that, yes I have tested the velocity of WST ammo at varied "Middle" temps between 32 - 110 degrees and the velocity change tracked pretty consistently with the temp change.

 

Lastly, yes there are matches hosted in temps north of 110 degrees. More importantly, there are major matches with chrono stages were the staff leaves the ammo sitting in the sun so the ammo is HOT when you chrono it vs the ambient temp.

100 percent the last thing... Noticing that is what started me chronoing my ammo after heating and cooling it.

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On 4/10/2022 at 9:14 AM, OpenshooterAclass4lyfe said:

Slightly off topic.  How did your friend get bumped to open? 

This was probably 10 years ago.  Back then they still had the 500 gun rule in limited.   He had an SVI sight tracker that hadn't met the 500 mark yet and ran into Amadon at the safe table.  He got bumped to open and our next stage was chrono where he went minor.  

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It is fairly easy to test cold to hot temperature effects.50 rounds in the freezer overnight .(-40 deg). 50 rounds in the refrigerator overnight (40 ish deg).

50 rounds on a heating pad overnight (100/110 deg).50 rounds at room temperature(?) 

I chrono at home so no problem keeping at temps. If you have to travel you will need a few empty coolers to maintain the temperatures.(smaller the better).

Haven't tested WST . But several others. Clean shot was the worst. Over 200fps from extreme cold to hot.

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  • 2 months later...

Some numbers from February and this morning.

 

230 Grain Precision Delta FMJ, 4.8 WST, Winchester Brass, Winchester LPP, 1.255 OAL .470 taper crimp, fired from stock barrel Glock 21 Gen 4.

 

Chronograph numbers from February 6, 2022, temperature 30 degrees, 810,789,798,788,801 average 797.2.

Chronograph numbers from June 18, 2022, temperature 86 degrees, 760,768,767,761,760 average 763.2.

 

IME/IMO it is reverse temperature sensitive. Load is near maximum, please follow all safe reloading practices.

 

Just my .02,

LeonCarr

Edited by LeonCarr
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3 hours ago, LeonCarr said:

Some numbers from February and this morning.

 

230 Grain Precision Delta FMJ, 4.8 WST, Winchester Brass, Winchester LPP, 1.255 OAL .470 taper crimp, fired from stock barrel Glock 21 Gen 4.

 

Chronograph numbers from February 6, 2022, temperature 30 degrees, 810,789,798,788,801 average 797.2.

Chronograph numbers from June 18, 2022, temperature 86 degrees, 760,768,767,761,760 average 763.2.

 

IME/IMO it is reverse temperature sensitive. Load is near maximum, please follow all safe reloading practices.

 

Just my .02,

LeonCarr

Slower at higher temps but also more consistent. 
ES-8 VS ES-22

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8 hours ago, LeonCarr said:

Some numbers from February and this morning.

 

230 Grain Precision Delta FMJ, 4.8 WST, Winchester Brass, Winchester LPP, 1.255 OAL .470 taper crimp, fired from stock barrel Glock 21 Gen 4.

 

Chronograph numbers from February 6, 2022, temperature 30 degrees, 810,789,798,788,801 average 797.2.

Chronograph numbers from June 18, 2022, temperature 86 degrees, 760,768,767,761,760 average 763.2.

 

IME/IMO it is reverse temperature sensitive. Load is near maximum, please follow all safe reloading practices.

 

Just my .02,

LeonCarr

So it is over 4%. A load at 170PF during winter would not make a major PF with this temperature range 

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