Powder Temperature Stability The bottom line!

[mtn grizzly]

Hi All,

During the weekend, I was looking through the new Hodgdon Reloading Supplement and they had a chart showing the velocity deviations caused by temperature change among different powders. The bottom line - was that the chart showed an extreme velocity spread of only 8 fps when testing Varget (EXTREME) As compared to a whooping 50fps when testing R15 or N160!

Are you ready for this? The temperature variable range was 0 F to 125 F.

I pulled out my ballistic calculator and started running some "real world numbers". I happen to shoot a 6.5 X 47L (with Varget and 123 Scenars) What I found was that the difference between Varget temperature stability and R15 temperature stability amounted to .4" @ 300 yards and 2.2" @ 600 yards - THIS WITH 125 DEGREE CHANGE IN TEMPERATURE!

Given a "more reasonable" temperature variation that many of us experience - say maybe a 40 F swing - I would assume that the ballistic differential would be substantially less if not insignificant!.

Am I wrong on this?

I live in the Sacramento area so our weather is not as extreme as some of the weather that you tougher boys out there face but I do "try" to make it to Alaska every other year and so temperature stability is always in the back of my mind.

Sandwarrior, Bob and Erik C have all offered some great council on this subject. I am just wondering if we (precision minded shooters) sometimes make things more ominous than they really are.

Thank you for your thoughts!

Dan

 

[bowslngr]

Re: Powder Temperature Stability The bottom line!

sure would like to see somebody independantly put that to the test. I took a look at the graphs online and I would be surprised if the actual variation for most of the powders listed isn't higher than stated.

Would also be interesting to compare this data to what Quickload predicts. I have noticed that Quickload doesn't seem to cut the Hodgdon's Extreme powders any slack.

 

[Ratbert]

Re: Powder Temperature Stability The bottom line!

Try a 50fps delta @ 1000yds and see what you get. Then try it with a 175MK instead of your high BC 6.5 pill.

Also, even @ 600yds if you hold center mass that 2.2" damn near puts you off a 1MOA target.

In the end, it all comes down to how small you're wanting to shoot. If you're only interested in getting hits on cheap 3D organic knockoffs of full size IPSC targets @ 600 yds then no, it probably isn't significant.

 

[head2h2o]

Re: Powder Temperature Stability The bottom line!

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bowslngr</div><div class="ubbcode-body"> I took a look at the graphs online and I would be surprised if the actual variation for most of the powders listed isn't higher than stated.

</div></div>

I would have to agree with this. Another thing to consider is that the powders that you listed are stick powders, except the N160, which I have never used and cannot speak to. If you use any of the ball powders, they tend to be more temperature sensitive. I have noticed this with BL-C2 and AA2520. I have seen both of these act completely different in shifts of as little as 40 degrees. Here in SE TX, a cold day in the winter may only be in the 50's and then hot days in the summer run in the 90's. I have loaded rounds with the 2 powders above on those 50 degree days only to notice signs of over pressure on the 90 degree days. I actually experimented with this just to see if this was really what was happening. I took the rounds and kept them in the refrigerator and sitting on ice until I got ready to shoot them so that they would not be at teh ambient 90+ degree temperature and low and behold they started acting just like they did during load development in 50 degree weather. I have since discontinued using the BL-C2 in 308 for this reason.

 

[Fred_C_Dobbs]

Re: Powder Temperature Stability The bottom line!

The question goes beyond the temperature stability of the powder. All pressure behaves the same and all heat behaves the same, regardless of how it was created. Were the barrels allowed to stabilize at 0° and 125° before testing? Because even if the 0° charge developed the exact same level of energy as the 125° charge did (figure the odds!), more of that energy will end up in the barrel itself instead of contributing to driving the bullet. Even <span style="text-decoration: underline">if</span> you start with the exact same energy, unless it's a two inch barrel, it beggars belief that there would just be an 8 fps spread.

I could believe 8 fps if they used barrels with similar temperatures and only the temperature of the cartridge was different, but what relevance does that have to a hunter who hunts in both Montana and Old Mexico?

 

[Rob01]

Re: Powder Temperature Stability The bottom line!

I have tested Varget from single digits to around 100 degrees and only saw a 10fps spread. It's why I love the powder. I live in a colder climate but shoot in warmer ones most of the time so it's nice to know the velocity doesn't change much. I have done the same with H4350 and found about 15fps difference. Hodgdon's Extreme powders do what they say.

 

[Raider Power]

Re: Powder Temperature Stability The bottom line!

I haven't run any of my loads over a chrono to test how temps affect velocity, but I can speak to the pressure side a little. Most of my load development has been done in the summer in Texas which means temps in the 95+ range, and most o my shooting has been done in the fall or winter during hunting season when it can be in the 20s. I primarily shoot Benchmark through my .22-250 and it does not seem to be affected from my non scientific approach. My other load is H380 based and that load does open up in the cold. Still holds minute of coyote for as far out as I'm willing to shoot the
(about 400 yards) so I havent been real motivated to work on a less temperature sensitive load. This is a rifle that likes to be loaded right at maximum and shoots its best groups that way.

With my 7 rem mag, I load h1000 and have noticed zero variation/poi shift from load development to zero verification getting ready for hunting season in the fall.

 

[Michael]

Re: Powder Temperature Stability The bottom line!

Vaget doesn't move much, my experience mirrors Robs.
Do a load with N160 at 70 degrees at try it at 100 degrees.
It is not at all stable in temp swings and has a huge knee in the curve from about 50 degrees F downward.
Re15 swings but not as bad as N160, and certainly much greater than Varget.
The Hodgedon Extreme powders really do work.

 

[mtn grizzly]

Re: Powder Temperature Stability The bottom line!

Micheal

When you speak of R 15 and N160 being unstable - what kinds of shifts have you experienced velocity or pressure wise?

Thanks

 

[mtn grizzly]

Re: Powder Temperature Stability The bottom line!

Another Thought!

This past month, I have started doing a bunch of shooting at 1K with some of the Palma and F class boys. What I have learned is that with my current set up using my 6.5 X 47L with Varget and 123 Scenars - the elevation challenge is much simpler than I had expected and I can usually maintain 5" of vertical at that distance. The windage issue however is a different issue. It has me constantly scratching my bald head!

My point is that it seams that any powder stability issues (within reason) that a shooter was experiencing would be resolved with a quick twist of the turret - after his first sighter. Then you could spend the rest of the day fighting the wind with me!

Am I all wet on this?

 

[BOLTRIPPER]

Re: Powder Temperature Stability The bottom line!

i had lunch with famous published long range shooter some years back, and got told a story about Famous shooters son doing testing for some well known powder maker.......seems he was loading rounds into a hot chamber and letting the round sit....before sending it.

contrary to his own published preachings.

up shot was there was very little vertical variance and little to no velocity change.......read stable powder....as in the above posts.

winning,,,,,,,before charlie made it so.

 

[Erik Cortina]

Re: Powder Temperature Stability The bottom line!

I don't know about all this temperature unstable powders, and I'm not 100% sure I believe it makes that much difference.

I shoot F-Class, and one day I had a 14 shot run "clean" at 1000 yards, after that the conditions changed and I had already chambered my round, I load such that I can't pull the loaded round back out because the bullet will stick in the chamber. The temperature was about 85 degrees that day, I had already shot 16 shots including sighters that day, and then I let that round sit in my hot chamber for about 6 minutes. My condition never came back but since I was out of time I had to shoot, by then there were more shooters around me waiting to see what was going to happen, they kept saying "He's screwed, that round has been sitting in his chamber for about 6 minutes!"
Then I made my wind call and held "waterline", I hit an "X" for a clean 15x1000 match! That was with Hodgdon powder in my 284 Shehane.

I have also done the same thing in my 6.5x47 with N550, but not as long, maybe two minutes, and again, no change.

So, I have done the same thing with two different types of powders (Hodgdon and Vihta Vuori). Is it temperature stability or well tuned rifles? Maybe a little of both!

Erik Cortina