Temperature Effects on WST

[chiltech500]

Hi,

Can anyone experienced with WST give me a rough idea of effects of temps at 40 degrees vs say 75-80 degrees?

I'm using 4.3 gr for a 2oo gr LSWC in a 1911.

Thanks

 

[CZ9shooter]

I used to have some notes somewhere describing my experiance with WST in 9mm and 125gr cast bullets. It is in fact inverse temp sensitive.

Going from around 70° to 20° gave me an increase in velocity. Both chrono tests were done from the same batch of ammo. I don't remember exactly how much, but I didnt consider it significant. Something like 40fps difference on average.

 

[chiltech500]

I thought I read someone indicate that somewhere in a thread - maybe it was you.

Not significant is the part that interests me. Thanks

 

[gahunter12]

I loaded .40s&w for years using WST for my IDPA loads. It is indeed reverse temp sensitive, but manageable. I worked my load, chrono'd it in the spring while temps were in the mid 60's. I always like my loads to be 5 above on the PF, so they came in at 725fps with a PF of 130.5. That summer I chrono'd the same load, and still came in at 717fps with a PF of 129.06, and temps in the low 90's. That following winter I once again chrono'd them at 732fps with a PF of 131.7, and temps in the upper 30's/lower40's. After the first year I adjusted my load for the summer .1gr just to have that 5pf safety cushion for bigger matches. The ONLY trouble I ever had with WST was 2 summers ago I shot a match that had very little shade, and only enough room under the roof at each bay to sit. There for I had to leave my cart with my range bag, and cooler out in the sun. After lunch I had a few really weak rounds that failed to cycle my slide fully. It hit me that my ammo was getting too hot, so I placed my ammo boxes in a pocket on my soft sided cooler to cool them down. Since then I have never had issue.

 

[chiltech500]

Thank you, very interesting.

 

[jmr40]

Even the worst powders aren't effected enough between 20-70 degrees to even show up. Especially with handgun loads. If you are shooting well above 90 degrees and/or around zero and below you start to see differences, especially with rifles at ranges of over 300 yards. Even with 100+ degree temp swings there isn't enough velocity difference to be noticeable at close range.

 

[chiltech500]

Thanks JMR, I shoot for NRA Bullseye handgun minimum 25 yards. My loads are low velocity, not high pressure, i.e 45acp, 38sp, 22, so temp may have less affect on my rounds than say a 40 S&W or a 357 sig.

Would you say above 85 degrees things could change? We don't get much more than 85 in the summer, maybe a couple of weeks when it hits the 90's.

 

[Toprudder]

I have a friend that loves to use VV N-310 in 45acp, he says it is very temp sensitive, enough that if he shoots his normal load in temps less than 40 degrees, it won't cycle his gun reliably.