Good rifle powders for ≥90° weather?

Varget is pretty stable, that's the only one I use.

Varget has a very low 0.19 fps/F change for the powders I know of. This came off of accurate shooter link which is now gone. Most any of the newer Enduro powders from IMR are suppose to be less temp sensitive than the older powders. A lot of the RL-?? powders I have seen are very sensitive to temperature change. The RL-22 is almost 2fps/F. Do not know anything about the RL-26.

I've use Varget in the 260 with good results. Was using the newer Sierra 130gr HPBT GK bullet. I like the H4350 in my 6.5CM.

Varget and RL15 are both temp stable in 308. Those may not be good choices in 243 or 260. H4350 or imr 4451 are better choices in those and are also temp stable

Most load data is shown at 70 degrees. You'll have to get a hotter than 90 to have issues. But 120 or hotter is certainly possible.in some places

I like H4350 in that range of powders, its stable, offers decent velocity, and rarely lacks for accuracy.
Ive used a number of powders in conditions in the low 50s to low 100s (sometimes on the same day), and have found little real issue with good loads. Most of what i shoot are in hodgdons "extreme" line, but im itching to have a reason to try some of the new Endurons.
I have not used the RL series, besides some RL7, and dont have enough experience to comment on those.

varget and 4895.

Hodgdon "Extreme" powders,-- Varget for .308, H4350 for .260.

I am a big fan of Goldbond powder in high heat but I suppose the other suggestions are good too.

ewlyon said:

I am a big fan of Goldbond powder in high heat but I suppose the other suggestions are good too.

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I'm a fan of the anti-monkey butt powder, myself.

https://www.bedbathandbeyond.com/store/product/anti-monkey-butt-reg-6-oz-anti-friction-powder-with-calamine/

And wow, did this thread jump OT quickly. LOL

Hodgdon H series powders are supposed to be temp stable . I use H4895 for most of my rifle shooting and like it.

I looked into this once along with shelf life and came across some testing the military had done .

I want to say double base extruded powders were most stable and many ball powders could be quite temperamental with both temp and pressure spikes along with having a shorter shelf life .

If concerned, just use powders with the words "Extreme" or "Enduron" on the label as those listed with a temperature coating.

The real question is that since the OP has heard that temps of 85+deg cause pressure spikes, who is going to warn all those shooters at Camp Perry?

Nobody has mentioned the three temp stable (by design) rifle powders in our Reloder(R) line.
On the fast end, and designed for 308Win is AR-Comp. It is faster burning than Reloder 15 and Varget, about 4895 speed range. It is very temp stable, and quite probably the flattest, depending on the lot and application/components.
In the 4350 speed band is Reloder 16, which is growing on an amazing trajectory, because it is that good. Again, very temp stable.
On the slow burning/magnum side is Reloder 23. This powder is also extremely stable, especially at hot, and it is similar burn speed to Reloder 22. In some applications it is slower burning, and some it appears a little faster, so check our load data on that powder for starting point (reduce 10% from our max data).
Please don't take my word on this alone, and do some searching on these powders. Better yet, try some and experience this world class performance.
Shoot well,
Paul

^ thanks for chiming in Paul, nice to see company representation on the forums!
I still haven't seen any of the newer RL powders available here.... honestly didn't know they existed. I'll go pester the shops and see what they can get.

I'm a fan of the anti-monkey butt powder, myself.

https://www.bedbathandbeyond.com/store/product/anti-monkey-butt-reg-6-oz-anti-friction-powder-with-calamine/

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Soon to be 100+ for a couple months where I'm at may need totry that powder.

Thanks for the info Paul, nice to know about Alliant's temp stable powders.
Good to point out that RL16 and RL23 are temp stable as some of the RL powders had a rep for not being temp stable.

Legionnaire,
Regarding Reloder(R) 26, it's design utilizes completely different process technology than Swedish TZ(R) produced Reloders I have mentioned in this thread. Nitrochemie's EI(R) (Extruded Impregnated) technology provides unmatched ballistic efficiency, and is somewhat tunable for temperature response, but is not generally designed to deliver the flat extreme temperature response the TZ materials are capable of. Having said that, I have measured temp response in some applications that is quite good, but again, that will depend on each individual application and component set.
We do not claim Reloder 26 is a "temp stable" material, but rather it will typically increase pressure and velocity as temps increase, and the opposite as temps decline. The magnitude of the P/V changes are generally moderate, and it is up to the individual reloader to characterize his load in the range he will be using.
Shoot well,
Paul

cougar1717 said:

The real question is that since the OP has heard that temps of 85+deg cause pressure spikes, who is going to warn all those shooters at Camp Perry?

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Experienced target shooters have all seen and experienced pressure problems, and they also understand that heat does not help things. I remember pulling targets next to an AMU shooter, nice kid, and I gave my opinion that their ammunition was way too hot. The previous year I had picked up 600 yard brass from one AMU shooter, all the primers were loose and blown. The kid claimed the AMU had toned down their ammunition for this year, and he was not happy, because he wanted it hotter. At 600 yards slow fire, that AMU kid shooter had a blown primer, it had gotten down inside his lower, and I saw him with the lower detached from the upper, banging the lower on the ground, trying to get that primer out of the trigger mechanism. He must have, because had assembled his rifle, and fired off a shot, which was way out of the ten ring, ruining his score and his ranking. All that time when he was fooling with his rifle, the wind had changed, and he was minutes behind the wind changes.

Lots of shooters show up at the National Matches with ammunition developed in cooler weather, and there are always alibi relays. An alibi just ruins your score, you never want an alibi. I learned, by shooting my ammunition in 90 degree weather, to cut my loads, and keep on cutting till everything extracted perfectly. The trade off between increased velocity, and reliability, is always in favor of reliability. There is absolutely no reason to spend an entire season, practicing, attending regionals, only to have malfunctions due to over pressure ammunition at the Nationals.

If you shoot enough, you will find that pressure is not your friend. It does not like you, wants to bite you in the butt the first chance it can, and it will. While I have heard Varget is less temperature sensitive than others, I have seen lots of blown primers, on the firing line, with Varget loads, in 223 and 308 Win. These extreme powders are supposed to be less temperature sensitive than others, but I don't have a pressure gage to measure the phenomena, and because of the pressure indications I have seen, I am not going to trust advertising to protect me from over pressure loads.

If you are worried about sticking cases, pierced primers, and blown primers, the absolute most positive means to address this is to cut your loads.

The military uses the same ammo for all climates.
Just avoid maximum loads or work up your loads in the summer temps. I just avoid shooting any hot loads above 90F.

One July 4th it was forecast to be hot so I went to the range and found it empty and 103 F. A wet towel was placed over the back of my neck. Shooting in the shade with cast bullets and reduced loads produced a lot of smoke from the near melted bullet lube.
Keep your ammo in a ice chest if you have to.

Ireload2 said:

The military uses the same ammo for all climates.

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That is a very open ended statement, and yes, the military uses the same ammunition in the same weapons world wide. But they know what they are doing. These are excerpts from some 5.56 ammunition specifications:


from MIL-C-9963F, MILITARY SPECIFICATION CARTRIDGE, 5,56MM, BALL, M193


3.1 -General. - The cartridge shall comply with Drawing D10523632, referenced specifications and the following:

3.2 Bullet extraction. - The force required to extract the bullet from the cartridge case shall be not less than 35 pounds.

3.3 Residual stress. - The cartridge case shall not split when subjected to a 1% mercurous nitrate solution for 15 minutes.

3.4 Waterproof. - The cartridge shall not release more than one bubble of air when subjected to an internal pressure differential of 7 1/2 pounds per square inch (psi) for 30 seconds.

3.5 Accuracy. - The average of the mean radii of all targets of the sample cartridges, fired at 200 yards, shall not exceed 2.0 inches.

3.6 Velocity.-The average velocity of the sample cartridges, conditioned at 70° + 20 Fahrenheit (F), shall be 3165 feet per second (ft/sec) plus or minus 40 ft/sec, at 78 feet from the muzzle of the weapon. The standard deviation of the velocities shall not exceed 40 ft/sec,

3.7 Chamber pressure.

3.7.1 Measurement by copper-crush cylinder.-The average chamber pressure of the sample cartridges, conditioned at 70° 5 2OF, shall not exceed 52,000 pounds per square inch (PSI). The average chamber pressure plus three standard deviations of chamber pressure shall not exceed 58,000 PSI.

3.7.2 Measurement by piezoelectric transducer.-The average chamber pressure of the sample cartridges, conditioned at 70° +/- 2°F, shall not exceed 55,000 PSI. The average chamber pressure plus three standard deviations of chamber pressure shall not exceed 61,000 PSI.

3.8 Port pressure.

3.8.1 Measurement by copper-crush cylinder.-The average port pressure of the sample cartridges, conditioned at 70° +/- 2°F, shall be 15,000 PSI +/- 2000 PSI.

3.8.2 Measurement by piezoelectric transducer.-The average port pressure of the sample cartridges, conditioned at 70° +/- 2°F, shall be 15,000 PSI +/- 2000 PSI.

3.9 Temperature stability.-When the sample cartridges are subjected to the following storage conditions, the average velocity shall not decrease by more than 250 ft/sec and the average chamber pressure by either method used in 3.7 shall not increase by more than 5000 PSI, the average port pressure by either method used in 3.8 shall neither increase nor decrease by more than 2000 PSI with respect to the average velocity, chamber pressure and port pressure of the sample cartridges of
the same lot, conditioned at 70° + 2 F for a minimum of twenty minutes. Any increases in velocity and decreases in chamber pressure of the sample cartridges under these temperature conditions are acceptable,


MIL-C-70460A
CARTRIDGE, 5.56mm, BALL, (HEAVY BULLET) REFERENCE 1984

Delete in its entirety and substitute the following:

1995 version

3.7 Chamber pressure
The average chamber pressure of the sample cartridges, conditioned at 70 degrees plus or minus 2 degrees F, shall not exceed 58,700 psi. Neither the chamber pressure of an individual sample test cartridge nor the average chamber pressure plus three standard deviations of chamber pressure shall exceed 64,700 psi.

1984 version

3.7 Chamber pressure. The average chamber pressure of the sample cartridges, conditioned at 700 + 2oF shall not exceed 55,000 psi. Neither the chamber pressure of an individual sample test cartridge or the average chamber pressure plus three standard deviations of chamber pressure shall exceed 61,000 psi. The standard deviation shall not exceed 1900 psi.

3.6 Velocity. The average velocity of the cartridges when conditioned at 70 degrees plus or minus 2 degrees Fahrenheit (F) shall be 3,020 feet per second (fps) plus or minus 40 fps at 78 feet from the muzzle of the weapon. The standard deviation of the velocities shall not exceed 20 fps.

3.7 Chamber pressure. The average chamber pressure of the sample cartridges, conditioned at 70 degrees plus or minus 2 degrees F, shall not exceed 58,700 psi. Neither the chamber pressure of an individual sample test cartridge nor the average chamber pressure plus three standard deviations of chamber pressure shall exceed 64,700 psi.

3.8 Port pressure. The mean port pressure minus three standard deviations shall not be less than 15,600 psi for sample cartridges conditioned at 70 degrees plus or minus 2 degrees F.

There is a significant difference between the resources and testing of Army Ammunition Plants and home reloaders. At best, the home reloader has some sort of computer program that predicts pressures, (same program might also predict the stock market and the weather!) and maybe the shooter goes to the range and has a chronograph. I have never met, nor read a post by, a reloader who has his own ballistic laboratory, complete with pressure barrel, pressure transducers, and firing range. The average reloader looks at gross indications of pressure, basically malfunctions, failures to extract, blown or leaking primers, and from that, comes up with nonsensical prognostications of operating pressures. But since the home reloader does not have a pressure barrel, all his pressure predictions are no better than reading tea leaves from the bottom of a tea cup.

So, the Army actually knows what pressures its ammunition is operating at, sets limits for temperature stability, not only for breech pressure, but for gas port pressure, and if the ammunition is not acting reliably, the Army can change those limits any time it wants.

Slamfire what is your point?
You have only stated the obvious. People have been reloading since the beginning of metallic cased ammo without a lab. There is nothing nonsensical about case head expansion. If my cases last 20 to 50 reloads I think the loads have been proven safe.
Having worked in an aerospace company I am very familiar with the military specifications for everything from toilet paper to nuclear fuses. Why would I be impressed with a US government military ammo spec when I don't shoot US military rifles or ammo? I shoot much older stuff that has little data in most cases and I have no trouble staying safe.

If a hand loader is so ignorant he cannot reduce a load for use in the heat then he should not be reloading. I have been shooting reloads in the Texas heat all my reloading life of about 50 years. All I can say is it is no big deal.
If you are so obsessed with that last 50 fps of velocity that you blow yourself up that is part of the cost of your obsession.