Powder temperature sensitivity?

[pepperbelly]

For some reason I was under the impression that Varget was relatively sensitive to temperature changes. I also thought that RL-15 was fairly insensitive.

I read a post here that basically states the opposite.

Here in North Texas we get a pretty wide temperature swing- sometimes from one week to the next. I really want to decide on a stable powder before I work up a load. I have about 2 pounds of RL-15 right now.
I also don't want to work up a load now while it's cold and have a pressure problem in summer when it hits 100*.

Jim

 

[caustic]

Re: Powder temperature sensitivity?

my understanding is varget is the more stable one.

 

[spot69221]

Re: Powder temperature sensitivity?

Varget is a more temperature stable powder of the 2 in comparison. Typically RL15 will net a bit more velocity though.

 

[Krav69]

Re: Powder temperature sensitivity?

Cold is a relative thing, but the RL-15 that I dial with in 90F weather is miserable and requires a complete overhaul of my data book in 20F weather.

I guess RL-15 is "stable" at cold temperatures, but as of last weekend, not really <span style="font-style: italic">consistent</span> shot-to-shot, and it's killing my scores.

I'd sure like to see a comparative study undertaken to solve this issue, a little study of RL-15 versus Varget.

 

[sobrbiker883]

Re: Powder temperature sensitivity?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: pepperbelly</div><div class="ubbcode-body">
I also don't want to work up a load now while it's cold and have a pressure problem in summer when it hits 100*.

Jim

</div></div>

IMR4895 has actually proven itself to be real stable in my experience. 1/2 moa difference in my 500yd dope from Feb vs August, and here, that's a pretty big swing....

 

[caustic]

Re: Powder temperature sensitivity?

All I know is that RL22 in my 300 win mag is very UNstable from temps of +10C to -30C there is a BIG drop in poi.

I'm looking at trying H4831 or H1000 to see what happens, unless someone here has already done so.

 

[Tripwire]

Re: Powder temperature sensitivity?

Proper implementation of the OCW principles during load work-up will seriously knock the sharp edge off of "temp sensitivity".....

 

[Falar]

Re: Powder temperature sensitivity?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: pepperbelly</div><div class="ubbcode-body"> For some reason I was under the impression that Varget was relatively sensitive to temperature changes. I also thought that RL-15 was fairly insensitive.

I read a post here that basically states the opposite.

Here in North Texas we get a pretty wide temperature swing- sometimes from one week to the next. I really want to decide on a stable powder before I work up a load. I have about 2 pounds of RL-15 right now.
I also don't want to work up a load now while it's cold and have a pressure problem in summer when it hits 100*.

Jim

</div></div>

Search some of Kombayotch's posts, he has done some pretty good tests on temperature sensitivity of Varget vs Alliant powders. Varget is VERY temp insensitive while the alliant powders are the exact opposite.

RL 15,17,22 etc are all double-base powders like the VV N5xx series. These powders contain nitroglycerin which is why they are called double-base powders. This is why they will produce more velocity at the same pressure than single-base powders like the Hodgdon extreme series. However, nitro's energy content is readily affected by heat which causes them to be sensitive to temperature changes.

 

[vman]

Re: Powder temperature sensitivity?

Hmmmmm... I was wondering this myself today.

Went to the range and the temp was up probably 15 degrees more than what It was when I would have developed this load and my shooting today was not that impressive. I could not tell if it was wind, but I had some rather mediocre results. Hadnt cleaned the barrel either, and it took about 4-5 shots until I was satisfied that my zero was hitting where it should. Core bore should not take 4-5 shots to rid, especially on a warm day.

I have had this same load pump out clovered groups before, and sometimes not too satisfying.



Could I blame temp changes and varget? Probably not?

 

[Greg Langelius *]

Re: Powder temperature sensitivity?

Hodgdon Extreme propellents. Read down and take the <span style="font-style: italic">Extreme Tour</span>. Actual numbers can be pretty convincing.

While I've little doubt that questions like this one get a lot of people thinking, I'd just like to sew a few seeds of reality. Most of us forget about the human factor when we follow obscure trails in pursuit of absolute accuracy. We can get everything optimized and still blow the shot.

Under very controlled conditions three shooters will shoot differently with the same equipment and ammo. None of them are doing anything blatantly wrong, we just have to recognize that the human component is a very significant portion of the entire system, and we are each a little different.

Greg

 

[Tripwire]

Re: Powder temperature sensitivity?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: vman</div><div class="ubbcode-body">I have had this same load pump out clovered groups before, and sometimes not too satisfying.

</div></div>

Speaking entirely with respect to reasonable temperature differences as in normal winter conditions vs. normal summer conditions....and NOT with respect to the radical hypothetical bullshit of carrying a rifle from 50 below in Alaska to 140 above in South Texas for the sake of an internet argument.

Here the swing is as low as 0 or -1,-2 but normally 20 to 30 during deer season to 95/98 but normally 80ish during the dog days of summer. Not much different than most of the lower 48 aside from the duration of the Seasons.

Temperature's effect on the burning of a powder charge relates to differences in pressure, which translate to different velocities, and thus to different points of impact. A wide dispersion of pressure/velocity fired into the same group usually means a shitty group.

One of the default "benifits" of finding an OCW load is having that load work suprisingly well in a fairly wide plus/minus of case capacity. For that reason alone I quit weighing/sorting cases a long time ago. Case capacity as it's generally fretted by anal reloaders relates also to pressure differences, and in much of the same way a wide temp swing will affect a load.

Since a load worked up via OCW is much more forgiving with the case capacity of non-sorted brass as it relates to pressure/velocity/POI, then it also stands to reason that the effects of temerature differences are also forgiven to a certain degree, and even more so in sorted cases.

Much of the "temp sensitivity" hype is simply guys not running their shit in a good harmonics node that covers all the bases. There's very little voodoo or magic mystical fairy dust involved because the laws of physics are what they are, no more no less. OCW does not CURE the problems, but it sure as hell brings things into a zone that's easier to live with.

Just MHO, based soley on my experiences.......

 

[caustic]

Re: Powder temperature sensitivity?

I worked my load up using the ladder test ( was tested +20C to 0C) , during the fall with very good results and it held out quite well to about -10C..

But when the temp dropped one day during hunting to -30C that load went south.

I'm now looking into the OCW method Thanks for the suggestion, I might try to re work the RL22 Load (which is great in warmer weather) but still interested in developing a new load with more stable power.



In Manitoba it's not uncommon for our seasonal temp changes to go from summer +35C to winter -40C (+95f to -40f) which would be "normal", If I could get a stable load through that I'd be very happy , but it's not likely. What is likely I'm now that I’m thinking about it is that I'll need to work up a new load ASAP while it's still cold learn it's dope and run it all summer and learn how the dope has changed ( I’ll do this with this RL 22 as well). A big part of my problem that I had this year was that I hadn't shot the rl22 load in the extreme cold before so I didn't know how much to modify my aim. Unless someone has better powders in mind I’m planning on H 4831 or H1000, I read somewhere here that IMR 4895 might be good as well any other thoughts??

 

[caustic]

Re: Powder temperature sensitivity?

Thanks Greg , I just sent Hodgdon an email requesting more info since there tests were not done in "extreme cold" only 120F to 0F.

 

[pepperbelly]

Re: Powder temperature sensitivity?

Thanks for all of the replies. For some reason I just remembered them opposite. No real problem.
I have several powders on hand, but I am basically lazy and really don't want to work up a load for 3 or 4 different powders.
The reason I asked about this now is that I have a decent load using RL-15 and wanted to avoid risking pressure problems when it gets really warm. The last time I shot it the temp was about 40*. Today it's 72, but next week it will be back in the 20s. If it was just a slow, gradual temperature change from winter to summer it wouldn't be a problem. Here we can have a temp difference of 50* from one weekend to the next. That could possibly give problems.

Jim

 

[mattmc40]

Re: Powder temperature sensitivity?

great thread! informative!