chambered221 wrote:

slimjim wrote: I haven't been able to get my chrony to read the air rifle which was strange because it reads rubber bands. Try painting the projectile with a Sharpie !!! I've ran into the same issue with lead pistol bullets.

I've had to do that with rifle bullets.

Well, I've but together a list of powders and bullet to do some testing with to determine termperature sensitivity. I'm going to load 6 rounds for each line. I was going to go out on a 20F deg day, shoot 3-shots at ambient and then pull three from a cooler with hot rocks at 90+F and shot 3 more. Doesn't look like there is that cold of a day coming in the next couple of weeks. Another option would be to go out on a 60F day and two coolers, one at 90F and one below 30F, then shoot 2 shots at each temperature. That could be more telling if performance decrease isn't a straight line. Any thoughts?

223 64 BPB Varget
223 64 BPB TAC
223 64 BPB XBR
223 64 BPB CFE
223 69 SMK H335
223 69 SMK H4895


6.8 110 BTHP AA2200
6.8 110 TSX TAC
6.8 100 AB 1200r
6.8 90 HP__ Re7
6.8 95 TTSX Re10x
6.8 130 SMK LVR
6.8 130 SMK H335
6.8 130 SMK CFE
6.8 130 SMK TAC
6.8 130 SMK Varget
6.8 130 SMK 8208 XBR

270 130 SMK Varget
270 130 SMK 8208 XBR
270 130 TSX IMR4350
270 140 AB_ MagPro

I'm sure you loooove doing testing Slim...or is it just an excuse for range time and recoil therapy mate. Whichever way, we all appreciate your efforts mate...well done.

I am content to accept the manufacturers claims on temperature sensitivity. Only powders I use are ADI/Thales powders, other than a little Alliant Promo for shotshell loads. All the ADI/Thales (and Hogdon) powders are supposed to be good regardless of the temperature.

Vince wrote:

All the ADI/Thales (and Hogdon) powders are supposed to be good regardless of the temperature.

I'll be finding out. Was thinking this morning, I should throw in some magnum vs regular primers.

A two tier test that held temperature for each batch of powders as the constant and then had each batch repeated with mag primers and then without at each temperature would be certainly more informative. Two temperatures gives you a delta while three or more a rude corelation with the number of samples you are taking. Your biggest challenge will be keeping the rounds at the same temperature which will include letting the rifle chambers cool. Good luck and I look forward to seeing your results. Last week our temperature here fluctuated 20C in less than 24 hours. I have hunted on days where It was -5 when I left before dawn and got home at dusk and it was +14.

Slim,

Just heating and cooling the ammo won't give the true story. The firearm being testing needs to be at ambient temperature as well. The bolt face and chamber can warm/cool the brass of the case rather quickly. When testing cold temps, leave the rifle in your vehicle over night along with your ammo. Hot temps a rifle will heat up quickly enough on it's own.

Also, all temperatures are tested at 70F. Most temperature stability claims are mostly for colder weather. All powders are affected by heat to a degree. The "temperature stable" powders are supposed to be less effected than those not considered "temp stable" but you should see increased velocity/pressure when in hot temps.

new Id seen somefink somewhere
just went back and reread what the issue with M16 was all about when it was first adopted
the action/cartridge was initially tested using stick type powders but soon got changed to ball powder which caused the issues
and here is the weird bit the ball powder burnt slower for longer which stuffed up the timing, case was still expanded in chamber while extractor was trying to do its thing, leading to jamming and ripped off case heads/rims..aparently took a few years to get issue sorted.
so the two different type powders used (at a educated guess something like AR2206 and winchester 748 or BM2) not only have different burn rates they burn differently so it follows temp differences/tolerance should be different too.

Azar wrote:

Just heating and cooling the ammo won't give the true story. The firearm being testing needs to be at ambient temperature as well. The bolt face and chamber can warm/cool the brass of the case rather quickly.

That's why I want to test in 20-30F. Rifle will cool quickly. I will be switching between 4 rifles so there is time for them to cool. Start with 3 shots of cold ammo with a cold rifle, then load hot ammo in a now warm gun, then let cool.

There doesn't seem to be a lot of info on the web about powder sensitivity. Here are a couple interesting links I found. First is some testing done on powder temperature where he found barrel temperature is just as important. I may have to read this a few times to make sure I absorb everything. The second is info from Accurate's Website and discusses how a insensitive powder can become sensitive to temperature change with different bullet weights and quantities of powder.


www.shootingsoftware.c...actors.pdf


www.ramshot.com/faq/

"Most of our powders are not insensitive, and will show some effect at hot and cold temperatures.

However, we test at -40F and +125F and the deviation in most cases are ca 3% to 5% at these extreme levels. Therefore most shooters do not notice much difference under normal practical hunting conditions.

More elaboration on the subject:

Complete temperature stability can only be achieved with tubular extruded powders designs, either with double base (NG) and/or with other coating technologies.

Because the ballistic performance at extreme temperature is completely dependant on the specific combination, it is very difficult to quantify and qualify.

Our standard powders perform very well at extreme temperatures, and usually pass the strict military requirements by a large margin.

This is a subject that is often fraught with misconceptions and inaccuracies.

The term is used loosely by manufacturers without qualifying the subject, and is obviously exploited for marketing purposes and perceptions.

The facts are:

Although powders can be improved, it’s really only possible with advanced coating procedures and additives which increase the cost.
A particular powder can be improved re temperature stability for certain combinations, within a certain envelope which is specific to the following three main parameters/aspects
The caliber.
The weight of the projectile/bullet.
The performance level.

If any of these parameters/aspects go beyond or outside the intended ratio/s, the results will change and the performance will sometimes be different.

It is also very important that when a comparison is made, that all conditions re weapon i.e. components primer, case, bullet and the velocity are equal, and preferably done at the same time on the same day."

After reading the pdf file, which points out the barrel temperature has as much an affect on velocity/pressure ad powder temperature, I'm thinking I should do 2-shot samples instead of 3-shot. The third shot would have too much barrel heat affect on the measured velocity.

I dont use a chrony and have only just got/getting my act together (thanks for the prod Slim) at getting reloading consistent.today its hot 75 inside shady house with breeze more like 90 out where I was testing loads today. the AR2213sc loads were right up there to book max with absolutely no signs of excess pressure at all!!!! ears arent ringing/shoulder not bruised (oh thats right I have suppressor now ) cases extracted easy,bolt lift normal= butter smooth,primers same as factory fired at same time(for much worse group )
so I guess you could say its a stable load with heat and I wont have any worries going over pressure wise if temp changes. hmmmm maybe I can load em up even more...yeah nah, maybe a little but not going to chase the last bit possible
oh yeah 15 shots in strings of three, letting barrel/suppressor off, cool in shade between strings, barrel was uncomfortably hot to touch after 3rd shot and can hard to hang on to

Sounds good, Elvis. You can look forward to the cold weather to confirm your load is temperature insensitive.

LOOK FORWARD TO IT !!!!!HELLS BELLS batman if it doesnt rain soon we will all melt away

Elvis wrote:

:-x LOOK FORWARD TO IT !!!!!HELLS BELLS batman if it doesnt rain soon we will all melt away

Gee Elvis...you should be in my place at the moment mate...it's after 9pm and it's still 34 deg C.

Vince wrote:

Elvis wrote: :-x LOOK FORWARD TO IT !!!!!HELLS BELLS batman if it doesnt rain soon we will all melt away Gee Elvis...you should be in my place at the moment mate...it's after 9pm and it's still 34 deg C.

So Vince, are you also temperature sensitif? But your speed going down when temperature goes up?

And when you need rain, it might help to sponsor Suz. I've seen her in my dreams doing the rain dance a few times... and now my keyboard blocks...