Varying powder charge summer/winter?

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ben_g
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Joined: Sun Apr 24, 2016 7:37 pm

Varying powder charge summer/winter?

#1 Postby ben_g » Fri Jun 29, 2018 1:00 pm

Bit of a newbie question.

We all know that ambient temperature/ammo temp has some effect on velocity. I haven’t seen It severely affect groups in my previous open chambering using 2209 or 2208

I have just recently worked up a load in my Dasher with RL-15 that is showing much promise in our current temps of around 12-15 degrees Celsius.

My question is what sort of change in charge weight do people find they need to maintain the same velocity between winter (low teens) and summer (up to mid 30’s)?

I will of course test myself but looking for a ballpark figure with double based powder. Currently running 33.4gr which is running 3050fps, is the variation needed usually say a whole grain or even more or usually just a few tenths?

Hoping someone has some data and experience with this powder. I want to persist with it as I am comfortably in the higher node without any pressure signs.

Cheers

Ben.

RDavies
Posts: 1923
Joined: Sun Feb 12, 2006 7:23 pm
Location: Singleton NSW

Re: Varying powder charge summer/winter?

#2 Postby RDavies » Fri Jun 29, 2018 7:14 pm

With a Dasher sized cartridge and 2208, and those temperature differences, I would be changing the load by about 0.25gn.
RE15 is a lot more temperature sensitive and I haven't done any temperature tests with this powder, but I would guess it could require up to 0.5gn change????
Can you get AR-comp which is supposed to be very similar speed but much less temperature sensitive?

ben_g
Posts: 54
Joined: Sun Apr 24, 2016 7:37 pm

Re: Varying powder charge summer/winter?

#3 Postby ben_g » Sat Jun 30, 2018 8:22 am

Thanks rod.

Did a little digging online and in extreme tests (below freezing to high 40’s) RL 15 looks to be about 3 times more sensitive than 2208. About 1.6fps per degree vs 0.5

However that’s a basic interpolation of minimum and maximum and assuming the change is linear.
It would appear between 10 and 32 degrees RL-15 does not suffer too badly as the rate of increase flattens out at these temps.

I will just have to keep some data over the coming months and learn for myself.
So far Rl-15 is giving good results on paper and is significantly faster than 2206H, I lost faith in my current lot of 2208 in my 6.5x47L and haven’t yet tried it in the Dasher. I’m keeping it for fireforming loads.

Pommy Chris
Posts: 245
Joined: Tue Oct 21, 2014 12:05 pm

Re: Varying powder charge summer/winter?

#4 Postby Pommy Chris » Sun Jul 01, 2018 9:33 am

ben_g wrote:Thanks rod.

Did a little digging online and in extreme tests (below freezing to high 40’s) RL 15 looks to be about 3 times more sensitive than 2208. About 1.6fps per degree vs 0.5

However that’s a basic interpolation of minimum and maximum and assuming the change is linear.
It would appear between 10 and 32 degrees RL-15 does not suffer too badly as the rate of increase flattens out at these temps.

I will just have to keep some data over the coming months and learn for myself.
So far Rl-15 is giving good results on paper and is significantly faster than 2206H, I lost faith in my current lot of 2208 in my 6.5x47L and haven’t yet tried it in the Dasher. I’m keeping it for fireforming loads.

I did some tests with ball powders in a 308 and messed with temperature. Shooting at 600 yards with a round left in the sun on a car dash for 30 mins it made sod all difference to cool rounds. I repeated the test again putting a round in a freezer bag next to a frozen block and another in the sun first thing in the morning and the rest in the shade. The one in the bag went low and the hot one went high but similar tests with 2208 showed similar results. 2208 is supposed to be more temperature stable but IMO unless you do something silly and leave bullets in a hot car it wont make any difference form my results anyway..
Chris

RDavies
Posts: 1923
Joined: Sun Feb 12, 2006 7:23 pm
Location: Singleton NSW

Re: Varying powder charge summer/winter?

#5 Postby RDavies » Sun Jul 01, 2018 12:29 pm

Pommy Chris wrote:
ben_g wrote:Thanks rod.

Did a little digging online and in extreme tests (below freezing to high 40’s) RL 15 looks to be about 3 times more sensitive than 2208. About 1.6fps per degree vs 0.5

However that’s a basic interpolation of minimum and maximum and assuming the change is linear.
It would appear between 10 and 32 degrees RL-15 does not suffer too badly as the rate of increase flattens out at these temps.

I will just have to keep some data over the coming months and learn for myself.
So far Rl-15 is giving good results on paper and is significantly faster than 2206H, I lost faith in my current lot of 2208 in my 6.5x47L and haven’t yet tried it in the Dasher. I’m keeping it for fireforming loads.

I did some tests with ball powders in a 308 and messed with temperature. Shooting at 600 yards with a round left in the sun on a car dash for 30 mins it made sod all difference to cool rounds. I repeated the test again putting a round in a freezer bag next to a frozen block and another in the sun first thing in the morning and the rest in the shade. The one in the bag went low and the hot one went high but similar tests with 2208 showed similar results. 2208 is supposed to be more temperature stable but IMO unless you do something silly and leave bullets in a hot car it wont make any difference form my results anyway..
Chris

My results with W748 showed very definite differences between hot and cold weather. Once I got the bolt back from Matt, with a new extractor, I stuck with ADI powders after that. I suspect that RE15 would be one where small temp differences do matter.


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