How do you do your temperature sensitivity testing for your loads?

[gunsandgunsmithing]

On the 6PPC
200 Yards
1. 0.337
2. 0.271
3. 0.374
4. 0.264
5. 0.483

I dropped a total 3 tenths to keep it shooting. I screwed up the last group by fumbling the the case on the fifth shot. The first 4 we’re in a .250 or less. That cost me the yardage.

Bart

Generally speaking, that's about 20 degrees of temp change or about 1 mark on the tuner. Straight vertical? Pretty close to what you saw?
This is just my experience and how powder charge relates to tuner setting with a ppc/br case and proper powders.

 

[BartsBullets]

Generally speaking, that's about 20 degrees of temp change or about 1 mark on the tuner. Straight vertical? Pretty close to what you saw?
This is just my experience and how powder charge relates to tuner setting with a ppc/br case and proper powders.

Mike
It’s hard for me to say. I’m bad to tune with powder and just nudge the tuner to really sharpen the tune. That was a strange day. The load changed nearly every time we went to the bench. I’d say maybe 1 1/2 to 2 marks.

 

[K Hope]

^^^^This^^^^
Smokeless powder converting from a solid to a gas is a chemical reaction and all chemical reactions are temperature dependent, to varying degrees. Bottom line, as temp increases, they make more energy and hence, velocity. Yes, some are more sensitive than others but temp affects all chemical reactions and in bore time of the bullet, which affects tune. It nearly defines what tune is in that tune is about timing bullet exit with muzzle position. Before tuners, we altered exit timing. With tuners, we affect muzzle position relative to exit time. Both methods work and work similarly due to this correlation of exit time and muzzle position.
Once you're familiar with either method, it's a matter of staying on top of that timing. Tuners make it easy, when used properly and, they're literally at your fingertips. Ultimately, group shapes tell us a lot about relative tune, both ways. Moving a tuner or changing powder charge is best done with a method to the madness, not randomness. So, learn to read group shapes relative to powder charge and/or tuner setting../and you're on the right path.
The point of all of this is that with a tuner, powder sensitivity is not a huge deal. Sure, I like when there is a nice wide tune window but as long as I know what the groups are telling me, I simply move the tuner or change the load accordingly.

I have zero experience with tuners and just asking but, would not operating temperature (rifle and ammo) not affect tune more than ambient temperature. I have seen many shooters in the heat of a match change their shootings style sending a lot of rounds down range quickly; often with marginal success.

Also asking as, I am questioning if there is a one size fits all approach for tuner adjustments: If two identical rifles were set up side by side but used powders with different ignition times and or moisture content, could that not possibly mean tuners requiring different adjustments. One moving in and the other moving out?

 

[gunsandgunsmithing]

I have zero experience with tuners and just asking but, would not operating temperature (rifle and ammo) not affect tune more than ambient temperature. I have seen many shooters in the heat of a match change their shootings style sending a lot of rounds down range quickly; often with marginal success.

Also asking as, I am questioning if there is a one size fits all approach for tuner adjustments: If two identical rifles were set up side by side but used powders with different ignition times and or moisture content, could that not possibly mean tuners requiring different adjustments. One moving in and the other moving out?

Powder being a cellulose product, it's a pretty good insulator, so doesn't take on big temps swings rapidly in a warm chamber. No, I don't cook them to find that point. Rather, I haven't changed my shooting style in regard to how long I'll let a round cook in a hot bbl. So, no..I have not noticed it but I don't think a tuner is a cure for that scenario and I still choose to avoid it...just like before.

The rest of your question is pretty much addressed in the quote you used in your post. Ultimately, the only 100% method is to learn to read group shapes. Just like we did before tuners. If you don't have or can't see sighters, then it's really about reading your last group and good notes...just like before tuners.
As for moisture in the powder...I don't know except to say that it's taking up powder space(volumetrically), so I'd assume it slows the bullet slightly, creating a later exit time. Once again though, same as before but a sine wave target test will show you which way and how far to move it when specific group shapes occur.
I'm more than happy to go over that in detail with you by phone. It's so much easier to use a tuner than lots of people make them out to be and others appear to be in search of an easy button. We've been looking for that button in tuning by powder charge for many years now.

One may exist but to date, Bryan's testing hasn't been done over much temp change, only pressure. Both are factors to tune and pressure appears to have an offsetting affect to rising temps. If they always followed the same curve, maybe guns would never go out of tune..but they don't and tune changes. His findings about pressure being without a significant temp swing surely hold value but air density(sorry, should've been using that word all along) follows temp, warm air being less dense than cold, etc, can only be counted on if you map out a ton of possible temp/density scenarios, weighting each properly...and that changes too. Extreme heat has more effect on powder than mild, same temp swing. See how an easy formula may be difficult to ever attain? The good news is that the sine test answers how to move it, when and how far.

I'd be happy to discuss it more with you this week.--Mike

 

[K Hope]

Powder being a cellulose product, it's a pretty good insulator, so doesn't take on big temps swings rapidly in a warm chamber. No, I don't cook them to find that point. Rather, I haven't changed my shooting style in regard to how long I'll let a round cook in a hot bbl. So, no..I have not noticed it but I don't think a tuner is a cure for that scenario and I still choose to avoid it...just like before.

The rest of your question is pretty much addressed in the quote you used in your post. Ultimately, the only 100% method is to learn to read group shapes. Just like we did before tuners. If you don't have or can't see sighters, then it's really about reading your last group and good notes...just like before tuners.
As for moisture in the powder...I don't know except to say that it's taking up powder space(volumetrically), so I'd assume it slows the bullet slightly, creating a later exit time. Once again though, same as before but a sine wave target test will show you which way and how far to move it when specific group shapes occur.
I'm more than happy to go over that in detail with you by phone. It's so much easier to use a tuner than lots of people make them out to be and others appear to be in search of an easy button. We've been looking for that button in tuning by powder charge for many years now.

One may exist but to date, Bryan's testing hasn't been done over much temp change, only pressure. Both are factors to tune and pressure appears to have an offsetting affect to rising temps. If they always followed the same curve, maybe guns would never go out of tune..but they don't and tune changes. His findings about pressure being without a significant temp swing surely hold value but air density(sorry, should've been using that word all along) follows temp, warm air being less dense than cold, etc, can only be counted on if you map out a ton of possible temp/density scenarios, weighting each properly...and that changes too. Extreme heat has more effect on powder than mild, same temp swing. See how an easy formula may be difficult to ever attain? The good news is that the sine test answers how to move it, when and how far.

I'd be happy to discuss it more with you this week.--Mike

Thank you for your response. Much Appreciated!

As to temperature I was thinking more along the lines of D. Bramwell work on Barrel temperature and Ammo temperature. Most can avoid cooking a round but at some times it’s not so easy to control number of round sent down range looking for your condition.

As to ignition times whether it be a coating or moisture issue, I was thinking there would be a difference between; let’s say, an early or a delayed ignition resulting in a different recoil and barrel vibration.

Thanks!

 

[5spd]

In all the eons I've been reloading Ive never worried about temp sensitivity, never.
Just load and shoot.

 

[gunsandgunsmithing]

In all the eons I've been reloading Ive never worried about temp sensitivity, never.
Just load and shoot.

Do you compete? What discipline?

 

[gunsandgunsmithing]

Thank you for your response. Much Appreciated!

As to temperature I was thinking more along the lines of D. Bramwell work on Barrel temperature and Ammo temperature. Most can avoid cooking a round but at some times it’s not so easy to control number of round sent down range looking for your condition.

As to ignition times whether it be a coating or moisture issue, I was thinking there would be a difference between; let’s say, an early or a delayed ignition resulting in a different recoil and barrel vibration.

Thanks!

I read my groups and move the tuner accordingly if something has changed. Perhaps those things do change my tune. If so, I hope to fix it before going to record if at all possible.

It's amazing how often you'll move the tuner correctly by using temp alone but it's not 100%. It's also pretty amazing what computers can do these days, so it's certainly plausible to think that a program can be written that tells us exactly how and when to move a tuner but you first have to establish values and the values we know matter, change. So we are chasing a moving target but it's possible...IMHO. Then do we have to account for powder moisture and bbl temp? IDK.

 

[NorCalMikie]

MAX is XX grains for your powder. I back off maybe 1.5 grains, find my node and leave myself some "wiggle room". They're all going in the same hole.
You're loading at 70*, you hit the range and it 90* and you've left yourself some room for adjustment.
OR, you load to the MAX fire a couple of rounds and wonder why you have to beat the bolt open and where to send it to get a new bolt handle installed. AND, you wonder why your brass won't last??

 

[Dave M.]

From summer to winter I’ve seen the same load drop 50-70 fps. That’s with a 6BRA and H4895.

Last week Shooting a 6PPC with N133 I watched velocity increase 30 fps from 60 to 80 dregrees.

Bart

And that’s with a very temp stable powder. I seen over 125fps using Hornady Superformance in a 28” barrel chambered in 6.5CM (this was the difference from 0F to 105F).
Dave

 

[gunsandgunsmithing]

And that’s with a very temp stable powder. I seen over 125fps using Hornady Superformance in a 28” barrel chambered in 6.5CM (this was the difference from 0F to 105F).
Dave

Some powders are certainly better than others with temp changes but they all do change. It's just physics. It's a chemical reaction.