Temperature Sensitivity Experience N560 and RL-26

Kmccord

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I had an experience with H1000 in my 28 Nosler, received my rifle first of October, I live in Northeast TX, and this was like the third batch of reloads I had going looking for better groups, it was hot that day right at 90, in the afternoon no shade my ammo box open the sun beating down on top of me and the equipment. The first three shots all work good, not a hot load by any means when I loaded them, but the next round after they had been exposed to the sun for a little while had a more considerable kick to it and the bolt was stiff. I thought this is odd, did I just miss throw a charge, fired the next round, same thing then it dawned on me when I picked up another round, this is sitting in the sun way too long.. I covered them up and put them in the shade of my pickup and after 20 minutes back to normal pressures.. I wonder at what temperature are the temp stable powders really tested at, I have never investigated how they measure or test but I know from experience, even with H1000 being temp stable, do not expose them in the sun for very long.
 

Veteran

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So book data is also a reference. They test those loads in a test barrel with xyz components. Unless you are shooting the exact same everything that is just a guide. I rarely get over book max because I run lapau, adg, peterson, etc brass. Those books use remington, winchester, hornady etc. IMHO I only use book data to get a starting reference point to conduct a velocity ladder test and ident pressure at what that particular set up is going to handle.

Most data I see on FPS/degree shows .3 for those powders. I have found it to be less in a creeds, 6.5-284, and PRC but it's a starting point I suppose.
The tables I am using for Vihtavuori shows they tested using 27.5 inch bbl. My barrel is 26 inches. They used Lapua Brass, so did I.
QL model and actual velocity tests for N560 from previous actual shooting was also used.
 

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BrentM

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I had an experience with H1000 in my 28 Nosler, received my rifle first of October, I live in Northeast TX, and this was like the third batch of reloads I had going looking for better groups, it was hot that day right at 90, in the afternoon no shade my ammo box open the sun beating down on top of me and the equipment. The first three shots all work good, not a hot load by any means when I loaded them, but the next round after they had been exposed to the sun for a little while had a more considerable kick to it and the bolt was stiff. I thought this is odd, did I just miss throw a charge, fired the next round, same thing then it dawned on me when I picked up another round, this is sitting in the sun way too long.. I covered them up and put them in the shade of my pickup and after 20 minutes back to normal pressures.. I wonder at what temperature are the temp stable powders really tested at, I have never investigated how they measure or test but I know from experience, even with H1000 being temp stable, do not expose them in the sun for very long.
I think people misunderstand the stabile claim. VV states temp stability as being predictable. The rate of velocity change is linear or predictable. Hodgdon does the whole extreme thing and states the powder is insensitive. Independent tests show there is very little velocity change in temps from 0-125. They have a list of cartridges showing the change on their site. What they don't tell you is where that charge is on the chart. Is the 3006 they tested with 4350 on the low, middle, or upper end?
 

Veteran

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I had an experience with H1000 in my 28 Nosler, received my rifle first of October, I live in Northeast TX, and this was like the third batch of reloads I had going looking for better groups, it was hot that day right at 90, in the afternoon no shade my ammo box open the sun beating down on top of me and the equipment. The first three shots all work good, not a hot load by any means when I loaded them, but the next round after they had been exposed to the sun for a little while had a more considerable kick to it and the bolt was stiff. I thought this is odd, did I just miss throw a charge, fired the next round, same thing then it dawned on me when I picked up another round, this is sitting in the sun way too long.. I covered them up and put them in the shade of my pickup and after 20 minutes back to normal pressures.. I wonder at what temperature are the temp stable powders really tested at, I have never investigated how they measure or test but I know from experience, even with H1000 being temp stable, do not expose them in the sun for very long.
Yes, this mirrors my experience, except I think the hot chamber, and the fact the barrel and chamber retain a lot more heat in those extreme temps mean that when you put your rounds in the chamber, they start heating up immediately.

Like I said, I only shot 15-20 rounds in 30 min. but I think it was just too hot outside for these powders in these conditions.
 

Veteran

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I think people misunderstand the stabile claim. VV states temp stability as being predictable. The rate of velocity change is linear or predictable. Hodgdon does the whole extreme thing and states the powder is insensitive. Independent tests show there is very little velocity change in temps from 0-125. They have a list of cartridges showing the change on their site. What they don't tell you is where that charge is on the chart. Is the 3006 they tested with 4350 on the low, middle, or upper end?
Good point, I am shooting charge weights near the maximums, so yes could be if I was shooting middle range charge weights I would not see as radical a change, because intuitively, it makes sense to me that on the margin when you are close to maximum, the effect on pressure and velocity due to temperature is gonna start to go up exponentially or slightly non linearly, and at least at a multiple of the normal rate of change they may state over a whole range of temps and charge weights.
 

BrentM

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Just out of curiousity, what do you have against QL or what is your bad experience with it? I find it a very useful guide especially when you tune it using your actual velocity data from shooting.
I'm betting he has the same experience as me..... people use it thinking its the gospel and not understanding it's a modeling tool. Unfortunately when people start a convo with according to QL..... it usually doesn't turn out good. I have a friend that argues to the death QL is the bible and if you deviate from it you are a moron. He is very intelligent so it's usually a rough convo. ha ha
 

COmtnman1

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I encountered the same problem with N570 last summer when I was working up a load for my 338-378 Wby mag & 300 gr. Bergers. I had much higher pressure when the temp was in the mid 90's than when I started my load development & the temp was in the 60-70 degree range.
 

SixDemonBag

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Parts unknown....
Well great..RL26 is my plan for 7SS (have H1000 too).

I am going to have to begin load development on my 7SS in late August because that is when I will be back in the states for a few days and then back to Europe for work until the late October hunting trip. I can expect the temps will be much different where I am loading (Georgia - hot) and where I will be hunting in October (Idaho - hopefully not). I guess I could do barrel break in and load development in August and take a day or two to finalize my hunting load before we depart in October.

Thoughts fellas?
 
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