ADI powders, summer and winter loads....

[DenisA]

I've always been told that ADI powders are not temperature sensitive.

I think the correct explanation might be that they are less temperature sensitive than some other powders.

I have a 600 round old .284W that I developed a 2940 fps, ar2209, 168gn VLD load for in much warmer times than we have now in SE QLD. I haven't changed powder or primers batches. I checked the MV a couple of weeks ago and it was down to 2900 fps. I haven't re-tweaked it yet to see what the powder difference is.

Vertical dispersion at the mid's has been more than what it has been. This load has never been vertically stable enough at the longs and therefore doesn't get used past the mid's.

What are the chances that season is the cause of my MV dropping by 40fps?

Do you guys run different charges of ADI powder for hot and cold seasons?

Would a barrel tuner be enough to bring the peak of the node down 40fps?

[johnk]

Denis,

I have a cute ballistic calculator that seems to closely align with Brian Litz' but that I've had for maybe 15 years.

I tweaked the external environments that are known to relate to ballistics - altitude, ambient temperature & relative humidity. While all changed down range predictions, none changed MV worth a damn, as I expected.

That leaves you to explore two other possibilities, I believe - an overlooked change in your prep & loading routine or storage temperature of the ammunition (off & on the range). I've concluded that you are talking about a totally new load, not leftovers.

John

[DenisA]

Thanks for chiming in John. You could well be right about it being something that I've done or preparation, routine, etc. That's what I'm trying to ascertain.

I guess it would be a question of, does the difference in the temperature of summer to winter affect internal ballistics that much via powder burn rate rather than effecting external ballistics via environmental conditions. The Magneto speed is at the muzzle where atmospherics haven't had a chance to affect external ballistics or trajectory yet.

[johnk]

The Yanks worry about loads crafted when it's snow time popping when it gets hot, but that's not quite the same thing.

I think I'll revise my call & say it could well be temperature related, based on the results we find in an Australian match rifle championship, when we (sometimes) finish at 1200 yards day one & shoot the same distance first up next day. Some find around 2 MOA more elevation is needed in the morning & when I run that backwards through the tables, it equates to more than your velocity difference. On the other hand, I haven't had that problem worth speaking of & that's maybe because I store my ammo protected from the environment.

However when the temperature range is so uniform all year as it is these days (I recall winter happened on June 6 this year), it's hard to be assertive in any direction.

[Barry Davies]

ADI Powders are temp. sensitive. However I can only speak for 2206, 2206H and 2208

Tests I carried out some years ago suggest that 2208 is worth a reduction of MV ( from summer to winter ) of about 2.5 f/s per degree c
.
Down in Vic that would be from around 30 c to 10 c so a 20 c change is worth 50 f/s. Been caught a couple of times before I worked out what was going on.
Easy fix is to run at or slightly above 3000 f/s ( say 3020 ) then the problem goes away. This of course only becomes a problem at 900 and beyond.
We found that retuning was not necessary depending upon just where in the barrel vibration sequence exiting of the projectile took place. Certainly needs checking though. Doubt that a tuner would compensate for 40 or 50 F/s ( unless it was rather heavy )
About 0.6 to 0.8 gns powder ( more or less ) would fix the problem though. ( that's 2208 )

[scott/r]

Denis is this the barrel that kept gaining speed? If so, it just may have settled.

[DenisA]

Denis is this the barrel that kept gaining speed? If so, it just may have settled.

No Scott that's the 300WSM. 2 guns doing the opposite things to me. I found that to be caused by the notorious hard carbon build up. I've polished that bore back to metal and I'll be running it on moly, tuning it clean and adjusting its cleaning regime to every day it's used with some light JB bore pasting.

ADI Powders are temp. sensitive. However I can only speak for 2206, 2206H and 2208

Tests I carried out some years ago suggest that 2208 is worth a reduction of MV ( from summer to winter ) of about 2.5 f/s per degree c
.
Down in Vic that would be from around 30 c to 10 c so a 20 c change is worth 50 f/s. Been caught a couple of times before I worked out what was going on.
Easy fix is to run at or slightly above 3000 f/s ( say 3020 ) then the problem goes away. This of course only becomes a problem at 900 and beyond.
We found that retuning was not necessary depending upon just where in the barrel vibration sequence exiting of the projectile took place. Certainly needs checking though. Doubt that a tuner would compensate for 40 or 50 F/s ( unless it was rather heavy )
About 0.6 to 0.8 gns powder ( more or less ) would fix the problem though. ( that's 2208 )

Thank you so much Barry. This is a very insightful post. Having read it, I think I should definitely continue looking down this path. I'd love to hear more about tuners for temp changes if anyone has anything else to ad.

[plumbs7]

Hi mate , yep I've found 2209 less sensitive than 2208 but there seems to be a difference and I have summer and winter loads. It was only last weekend I left my bullets in the Son and it seemed to staiblise the powder in the 22 deg c temp. There seems to be an optimal temp that these powders run at !

Easy way is chrony first up in the morning . Then warm the bullets up to body temp with them in ur pocket and re chrony !

[DenisA]

Hi mate , yep I've found 2209 less sensitive than 2208 but there seems to be a difference and I have summer and winter loads. It was only last weekend I left my bullets in the Son and it seemed to staiblise the powder in the 22 deg c temp. There seems to be an optimal temp that these powders run at !

Easy way is chrony first up in the morning . Then warm the bullets up to body temp with them in ur pocket and re chrony !

Might be the next fad mate, temperature controlled ammo cases. F-class shooters will be towing their Engels up to the mound.

[plumbs7]

Hi mate , yep I've found 2209 less sensitive than 2208 but there seems to be a difference and I have summer and winter loads. It was only last weekend I left my bullets in the Son and it seemed to staiblise the powder in the 22 deg c temp. There seems to be an optimal temp that these powders run at !

Easy way is chrony first up in the morning . Then warm the bullets up to body temp with them in ur pocket and re chrony !

Might be the next fad mate, temperature controlled ammo cases. F-class shooters will be towing their Engels up to the mound.

Haha! Along with sock barrel warmers , big rubbers and big knobs

[johnk]

Don't laugh. Back a few years now during a hot spell, one of the small bore shooters found his ammo shooting crap in the practice before the championship, so he slipped a brick of it into the crisper of the club fridge & blitzed them.

[Barry Davies]

Just to clarify.
My figures are for a 308 using 155 gn projectiles --sorry if I confused anybody. I only ever talk 308/155 as that is all we shoot.
It does highlight that caution is needed where you leave your ammo on hot days --definitely not in direct sunlight as that will make it worse, so too will cooking a round for any length of time in a hot barrel.
As well as burning rate being somewhat temp sensitive, ADI powders also change their Bulk Density with temp -in other words a specified weight ( load ) will occupy different volumes at different temps.
Certainly sufficiently so that a nicely filled case could well become a compressed load with sufficient temp. change.

[williada]

Barry, you would not believe I was just speaking to a bloke about your work a couple of days ago in relation to powder and I could not remember the details as it was so long ago. So Jacko if you read this, Barry has done you and others a favour.

Just adding with an edit, if people are concerned about SD's, then temperature does matter. Winter time now is a good time to start a mapping of your velocities over the chronograph with every 5 degrees Celcius or roughly 10 degrees Fahrenheit. Put the results on a spreadsheet and graph the result. The object being to load in a given tune velocity range taking into account the temperature. Electronic targets with the chronograph facility on your regular Saturday shoot could gather the data too. It will surprise you. If you used a tuner, then there is another bonus in the learning process. Just saying. David.

[DenisA]

Just adding with an edit, if people are concerned about SD's, then temperature does matter. Winter time now is a good time to start a mapping of your velocities over the chronograph with every 5 degrees Celcius or roughly 10 degrees Fahrenheit. Put the results on a spreadsheet and graph the result. The object being to load in a given tune velocity range taking into account the temperature. Electronic targets with the chronograph facility on your regular Saturday shoot could gather the data too. It will surprise you. If you used a tuner, then there is another bonus in the learning process. Just saying. David.

Hi David. This makes a lot of sense............ now. I don't know why it's taken me so long to realise that this needs to be done.

All the more reason to understand and use tuners.

Barry, thanks again for the info. Bulk density change is very interesting and I wouldn't have thought that would be the case without the powder being subject to humidity. Thanks.

I've got some excellent info from this thread. Thanks to those that have answered.

[browniedog]

hi if winter and summer loads differ in speed do you change loads for different shoots at different height above sea level or coastal to dry country heat
any thoughts
david