N133 weather performance.

[DngBat7]

Is there any good threads about n133 and how it is affected by temp and humidity? Learned a lot the last few years and wanting to know more about 133’s weather sensitivity’s. For me being in the northeast, I’m finding my ppc with 133 likes cooler dryer weather with a higher grain count then the warmer northeast weather. Looking for any kind of general advise on this.


Thanks

 

[jackieschmidt]

I generally tune 133 in my 6PPC by humidity. When the humidity is high, I shoot 30.2 grns with my own 68 grn FB.

If a front comes through, and the humidity drops down to 40% or below, I will generally up it to 30.5.

Out in Phoenix, where there is practically no humidity, I change powders, I have some early 2015 that works pretty good out there.

 

[DngBat7]

Thanks Jackie. So I guess I’m not to far off that shooting hotter in the dryer weather if I’m following you correctly. So 133 is more affected by humidity levels as opposed to temp levels?

 

[Benchrest Braxton]

why would you load more when humidity is low? sounds to me like that would produce the opposite of what you want when trying to maintain consistent velocities?

high humidity = wet powder (heavier kernels)
low humidity = dry powder (lighter kernels)

 

[boltfluter]

why would you load more when humidity is low? sounds to me like that would produce the opposite of what you want when trying to maintain consistent velocities?

high humidity = wet powder (heavier kernels)
low humidity = dry powder (lighter kernels)

Just a guess, but I believe they are referring more to external ballistics than internal ballistics.
Paul

 

[JMayo]

I shot 133 100yd hot summer and 40° saw no real change ... but I'm shooting 29.8

 

[Sleepyhollow]

I believe it's more about humidity and air density the actual Temps. I've been testing this, this winter. In SW Missouri were always humid winter or summer. My ppc love 30.3-30.6 of n133. Shot the other day and it was 30 degrees but humidity was 49%. Gun shot perfectly. So in my notes I've got to where humidity % and dew point % means more then air temperatures. And I base my tunes on those those number now

 

[Mulligan]

Wow,
I was just talking to a couple of shooters in the last few days about “mapping out” N-133. One of the fellas suggested I plot “record” station pressure along with what I had planned, dew point, relative humidity, and temperature. Station pressure is the actual atmospheric pressure measured where you are with no adjustments for elevation.
I live and mostly shoot in Western Colorado, it is fairly dry here. Think of Phoenix AZ, but 10-12 degrees cooler. These western valleys are very hot and dry.

For a few of us that are collaborating on figuring out N-133 in the desert, we have found that we can load N-133 if the RH is 40% or more. Below that, nearly everyone here shoots LT.

I’m not sure this post will be of any value to the OP, but wanted to follow along this thread and see what I can learn.
CW

 

[DngBat7]

I’m not sure this post will be of any value to the OP, but wanted to follow along this thread and see what I can learn.

Definitely of value. Glad you posted

 

[ShtrRdy]

I shot 133 100yd hot summer and 40° saw no real change ... but I'm shooting 29.8

I'm new at the benchrest game but I ended up with the same load as you and it seems to behave the same at 40 degrees as it did when I developed it at 90 degrees. This is with a 68 gr BT.

What bullet weight are you using?

 

[gunsandgunsmithing]

I think there's a lot of value in knowing this info, even at short range but way more so at long. With a tuner and sighters that you can see, it's a simple job to just tune it by group shape and size. But where sighters are limited or where they can can't be seen, such a formula would be a game changer. But, it has to be spot on, 100% to be of much value, imo. I do think there is a way to do it but I haven't figured it out and there are so many variables, being 100% right is the big challenge. If it's not 100%, then you just fall back on your last target and notes, as we've already been doing, so little was gained. But it's worth the effort, I do believe that. I just think it'll have even more value using powders used at long range vs n133, which is almost exclusive to short. Either way, I commend those doing the testing to learn more on this subject. I'd certainly like to know more myself. Keep up the good work.