Temperature Sensitivity of 8 Powders for .223 High Power Service Rifle

[urbanrifleman]

All powers are temp sensitive exactly the same amount.

It's been tested... none of this will make any difference.

At least that is what they told me in the other forum....

And AR Comp sucks... don't buy it.

 

[urbanrifleman]

Wait. Several of the powders show velocities declining with increase temp - what does that mean?

That is what AR COMP does. But basically the response is flat... the change is tiny.

 

[Ned Ludd]

QuickLOAD is worthless for predicting temperature sensitivity (or more specifically predicting the slope of the temperature/velocity relationship for the powder.) It appears to assume that all powders are temperature sensitive.

I went back and assessed the function of QuickLOAD in predicting temperature sensitivity with my data. First I adjusted the Ba (burning rate factor) value so that it was calibrated with the data I had for powder, bullet, case volume, temperature and velocity. I then had QuickLOAD calculate velocity predictions for the three temperatures at a given powder charge. The data are below. QuickLOAD assumes that the slope is positive for all four powders I checked regardless of whether the slope is positive, negative or flat.

View attachment 1272658View attachment 1272665

Unfortunately, a number of QuickLoad outputs/responses are perfectly linear, even though we know in the real world they are not. Your data provides a couple excellent examples of this in showing how the QL predictions of velocity versus temperature are linear, whereas your actual data show the velocity versus temperature response in fact, is not linear across a fairly wide temperature range. Not surprisingly, the same thing seems to be true in my hands regarding pressure as a function of charge weight, particularly as you approach or slightly exceed predicted MAX pressure. I have always found that the closer a calibration/test load is to the final load, the better the QL prediction will be. In other words, it's like a tangent line for a curve, the shorter the interval, the closer the response on the curve will behave as being close to linear. My gut feeling is that the computations and the number of variables for internal ballistics are so complex, there is a limit to what a simple computer program like QL can do, and so certain outputs are treated as being linear, when in reality they are not.

 

[BillC79]

I am following up on an issue previously raised and discussed with Ned Ludd. What is the effect of a warm (or hot) barrel chamber on the powder temperature and combustion? Also, I want to further address the question: Does any of this temperature-sensitivity and standard deviation measurement have any bearing on where your bullet hits down range (assuming perfect shooting technique and wind-reading ability?)

I performed additional tests trying to simulate shooting the second 10-round string of cartridges at 66°F in a rapid-fire sequence where cartridges are in the hot chamber for 5 seconds before being fired. I also simulated a slow-firing sequence where cartridges are in the chamber for shots 11 through 20 for 30 seconds each. I measure barrel chamber temperature with a digital oven thermometer with long stainless steel probe inserted into the chamber against the chamber wall.

Responses of a temperature sensitive powder (CFE 223) and less sensitive powder (AR-Comp) were compared. Unfortunately, the runs for each powder were about 15°F different, so I had to go through a normalization process to compare results. Finally, I plugged the muzzle velocity spread into a ballistic program based on means and standard deviation for each powder and shooting sequence and estimated the variation in impact point at 300 and 600 yards for both powders.

Interim Conclusion: Powders do get heated during rapid- and slow-fire sequences at chamber temperatures between 108°F and 142°F and result in significant changes in velocity. Degree of powder sensitivity to chamber-induced temperature change does significantly affect magnitude of velocity change. Resulting velocity variation does significantly affect impact spread of bullets at 300 yards and 600 yards and your point score and number of X’s at the end of the day.

The newest data panels follow. I have updated the methods section on the website review, but not the results and conclusions section (yet).

Thanks for looking and for ongoing comment and suggestions.

 

[RegionRat]

Agree with your conclusions Bill.

Soaking a round in a hot chamber is an effect one must understand and account for as a competitive shooter or varmint hunter.

Each game is a little different in terms of the tempo and if the shooter has a chance to adjust. When I started using CFE223 for prairie dog loads, I got into the habit of updating the dope as the morning and temperatures changed. I don't use it for Service Rifle, but it is manageable for PD work as long as you have a Kestrel or equivalent.

As I said earlier, I used to produce weapon systems that were often airborne. That means they may get cold soaked anywhere from -40 to -70 C and then go into action.

As time went on and we had radar tracking the rounds, I could watch the velocity and elevation changes as the guns warmed up, and then if there was a pause and that round that was parked in the chamber got much hotter than the others, it stuck out. It was very easy to observe with the FLIR once we had enough resolution and speed.

The better temperature compensated powders minimized this, and the other ones were obviously worse.

The good news in all this, is we have new powders that are going to keep the REACH folks and the shooters happy for a while. Appreciate you sharing your work. Well done.

 

[BillC79]

New vs Old Vihtavuori N140

The new N140 appears to be less temperature sensitive below 68°F (20°C) than the old. New N140 produces slightly higher velocity than the old at the same case charge with a 77 grain bullet. Both the new and the old N140 are very temperature sensitive above 68°F. With a case powder charge of 24.3 grains, both the old and the new N140 at 129°F (54°C) produce overpressure signs on primers (primers flattened and partially extruded from the primer pocket).






Note added: I am also posting this in a separate thread on this forum since I was unable to find any data online about new vs old N140.

 

[RegionRat]

Bill, I'm still running RL-15 and Varget, but many club mates started playing with N140 during supply gaps. Your work mirrors their experience with the old and new powders.

Good thing rapids are only 10 shots at 300...

Great post and thanks for sharing your work.

 

[BillC79]

The final temperature velocity graph follows with analysis for 4 newer powders to consider in comparison to Varget. IMR 4166 and AR-Comp were the best performers to consider as substitutes if you shoot at temperatures above 70°F. The temperature sensitivity of Lovex S062 was more closely comparable to that of N140 or CFE 223 than to Varget. I’m moving to working up accuracy loads for IMR 4166 and AR-Comp and will update the online review at:

Temperature Sensitivity of Powders for .223 High Power Service Rifle

Thank you to all who commented on the data and suggested improvements in the study.

 

[LVLAaron]

AR Comp still smokes them all in the practical shooting range of say 50 F to 110 F. Lowest spreads too.

AR-Comp is by far the best powder you can (could?) get. It provides almost unreal velocity, incredibly low SD, and everything I've shot it in... I get benchrest sized groups, even from an AR.

 

[urbanrifleman]

AR-Comp is by far the best powder you can (could?) get. It provides almost unreal velocity, incredibly low SD, and everything I've shot it in... I get benchrest sized groups, even from an AR.

Shhh... Ar comp sucks.

 

[urbanrifleman]

New vs Old Vihtavuori N140

The new N140 appears to be less temperature sensitive below 68°F (20°C) than the old. New N140 produces slightly higher velocity than the old at the same case charge with a 77 grain bullet. Both the new and the old N140 are very temperature sensitive above 68°F. With a case powder charge of 24.3 grains, both the old and the new N140 at 129°F (54°C) produce overpressure signs on primers (primers flattened and partially extruded from the primer pocket).

View attachment 1273960


View attachment 1273961

Note added: I am also posting this in a separate thread on this forum since I was unable to find any data online about new vs old N140.

Wow that's awful. How disappointing.

 

[LVLAaron]

Shhh... Ar comp sucks.

I'm generally pretty quiet about it to keep other people from buying it up. Shame on me.

 

[Laurie]

My N140 is the "old" formula purchased in 2020 (manufactured in 2017). The new "improved" N140 has a label that states "Decoppering agent and Temperature stable" in the UK according to Laurie Holland in Target Shooter Magazine. Link to article below:

HANDLOADING BENCH BY LAURIE HOLLAND

REACH OUT! – EU COMPLIANT POWDERS Part 1 Thinking of a name for this piece, the 1960s mega-hit for American boy-band The Four Tops popped up in my head. Bad news as Reach Out! [I’ll be there] is one of those tunes you can’t shake off for days. Still, it’s an appropriate bit of plagiarism…

www.targetshooter.co.uk

I found a bottle of the new N140 in stock and will test it against the old.

I've identified 27 'REACH' compliant grades as H4895/VarGet alternatives that are on paper anyway available to us in the UK. Three have unfortunately just dropped out as RUAG Ammotec UK has stopped importing the Norma range less than three years after reintroducing it. I managed to test most of the 16 extruded grades in the list last year in a 223 Rem F rifle using Lapua brass and the 77gn SMK alongside the two benchmark grades H4895 and VarGet. Of these, three aren't sold in the US - Reload Swiss RS40/50/52.

Writing up the issues and results of this stage has just started and will appear in sections in targetshooter.co.uk over the next few months.

A few initial comments. As usual burning rate charts and QuickLOAD show Viht powders as slower burning / producing lower pressures than usually applies in actual load combinations. Likewise, Lovex S-series single-based extrudeds, but in reverse - ie shown as faster burning / producing higher MVs than turns out in testing. S062 (SW 'Precision') appears to be rather slower burning than VarGet - in the 223/77 at any rate. Viht N140, N540, and surprisingly N550 gave outstanding results although 550 is rather heavily compressed in this application and were excellent VarGet replacements. Note too this was 10-year old N550, not the recently reformulated version. (N140/540 were newly purchased.) As various posts have noted, AR-Comp is a superb powder in this application, rather faster burning than either H4895 or VarGet though. IMR-4166 Enduron turned out to be a very 'odd' powder in the 223. First, although there is plenty of published data for its use in larger case-capacity numbers such as 308 Win, nobody, and I'll repeat, nobody publishes lab-tested pressure measured data for the 222/223 and similar small cartridges other than Hodgdon itself, and that with a very low maximum for 223/77 well down on the apparently comparable H4895. I loaded it up to my H4895 top charge weight in 10 X 4-round, then six X 5-round steps getting lower MVs than QuickLOAD predicted and hitting compressed status at a lower weight than with H4895. The top couple of charges that took it to my H4895 weight produced rather lower MVs than the ADI/Hodgdon grade, but also unlike the Hodgdon grade started to show pressure signs. The rifle chamber is minimum SAAMI case with a freebore between Wylde and the PT&G ISSF, likely somewhere a bit over 100 thou' allowing 2.400" COAL with the 77gn SMK and more room for powders like N550 and 4166.

 

[RegionRat]

As many have heard, Gordon of GRT fame has recently passed away.

In addition the the tragedy this creates for his wife and loved ones, it is also a loss for the shooting internal ballistics community. We can only hope that his family and loved ones are well cared for, and that his work can carry on.

Along with testing work from folks like Bill and Laurie, there is still more work to be done to characterize and understand these powders and model their temperature sensitivities.

Thanks for sharing your thoughts, @BillC79 , and @Laurie , good luck with the rest of the work.

 

[Laurie]

As many have heard, Gordon of GRT fame has recently passed away.

I hadn't heard that. A loss indeed.