T_the_Tinkerer
Hammer Time Executive member
As the title states, this is the combined temperature stability tests. This thread discusses the second test in detail..see the previous test for detailed discussion on the first test.
Description of test:
I used three general temperature windows to test: one at ambient temperature, one at a very cold and the last at very hot. These would simulate hunting in the spring/fall, the winter, and the summer, the first round that's sitting the chamber and the follow up shots one would take.
Procedures:
I used a freezer gel pack which sat in the freezer all night with (3) of each unique cartridge nestled inside, folded up. The temperature dropped well below zero while in the freezer. This went into a plastic cooler with ice.
I used a pair of battery powered muscle warmers wrapped in Aluminum foil and insulated in a cotton cloth for the hot test. This was kept in an insulated lunch bag, and left on the entire test.
Temperature was taken continuously with a 3-way temperature probe (-4°F~536°F); a temp gun was used on the cold cartridges when the temperature was outside of the probe's range.
Bullet used was the 75gr ELD-M, 223 Remington LC brass, Fed 205M primers, and no crimp. Powders and charges are shown in the images. Each charge was about 0.2gr below book max for SAAMI 223 Remington (55,000psi) as per Hodgdon and Vihtavuori online reloading tools.
I shot a single fouling shot at room temp before I began a [cold -> ambient -> hot] shot string with the same powder. (3) shots were taken of each temperature type. Between strings I let the barrel cool with the aid of alcohol infused wipes. Temperature was taken for each temp type just before loading them. Rounds were fired as quickly as possible once they were loaded in the chamber. Temperatures and velocities were recorded, and graphed with an online tool. Hurray for technology...too bad it took me a while to find that would plot the data I needed without trying to get my credit card info.
Discussion
If I had to do this test over I would omit the crimp (as I did for the second test). This test verified to me that some powders respond pressure-wise more severely than others; all three ambient temp velocities should be more or less the same in the above test. Perhaps AR Comp would have been a bit more stable if it lacked a crimp here...? The dotted line represents what AR Comp's curve would look like if I had a more granular means of testing the temperature response.
>>>Redid test w/ AR Comp & LT-32<<<
Cartridge details: 60gr HH, LC brass, BR-4, 25.2gr AR Comp or 23.8gr LT-32, no crimp (this is important, as AR Comp is far more neck tension sensitive than other powders I've tested, and it is known that LT-32 is as well).
AR Comp (test #2)
Cold: 2.5°F, avg velocity 3237fps
Cold to Ambient change: -30fps, -0.87% change
Ambient: 71°F, avg velocity 3207fps
Ambient to Hot change: 28fps, 0.73% change
Hot: 154°F, avg velocity 3235fps
Notes: much more bowl shaped curve than before, as the crimp increased pressure which increased cold pressure. Pressure and velocity should actually drop the most by about 115° or so, before going back up where you see it at here. Overall, very good regardless of cold or hot, but still not as good as we saw with Benchmark. I figured if I can actually get BM up to pressure it would show more sensitivity than last time.
LT-32
Cold: 3°F, avg velocity 3127fps
Cold to Ambient change: 83fps, 2.65% change
Ambient: 72°F, avg velocity 3210fps
Ambient to Hot change: 94fps, 2.99% change
Hot: 156°F, avg velocity 3306fps
Notes: definitely not as stable as the older T-32 it was based off of. While it was said to be more stable than N133, this is not the case anymore; many of the old BR guys likely have huge stashes of the old N133 before VV made steps to improve temp stability. Other than the low ES at all temps, the velocity swings too much for my tastes. Also to note, was that even though the cold temp velocity was the lowest, it had pressure signs!
Discussion
As you can see, behavior here was typical for what is expected with smokeless powder. This time I will list each powder individually, their total ES and within temp brackets, as well as provide any relevant commentary.
A2460
-8°F ~ 77°F: 118fps
77°F ~ 164°F: 149fps
avg: 1.55fps per degree
Comments:
like A2230, this powders has been shifted to production in multiple countries and this has not been stable in regards to temperature response in the last decade or two. Production is now here in Florida by St. Mark's. Also like A2230, temperature response has suffered and is what you would expect of a stereotypic spherical powder, as well as it's SD. It may perform better in larger capacity cartridges, though.
A2520
-8°F ~ 77°F: 110fps
77°F ~ 164°F: 228fps
avg: 1.97fps per degree
Comments:
Well, what can I say. HUGE spreads. In this powders defense, there were no pressure signs at all it had low SD in the cold. As Western stated in their FAQ, generally within a given style of powder, the slower varieties are more temperature sensitive than the faster ones. A2230 only had a spread of 162fps across nearly the same temperature range.
N133
-4°F ~ 78°F: 48fps
77°F ~ 165°F: 61fps
avg: 0.64fps per degree
Comments:
SD is best at ambient temperatures, but is still better in the extreme heat than the cold. Better than the last two, even at its worst. Has a copper fouling eliminator...but so does X-terminator. I guess this is typical temperature response for a non-Extreme extruded powder. Apparently it's changes are very predictable and benchrest shooters can account for it like clockwork.
N135
-4°F ~79°F: 35fps
79°F ~ 166°F: 74fps
avg: 0.64fps per degree
Comments:
Less heat stable and more cold stable than its little sister, N133, but larger SDs. Both get excellent velocities with proper bullet weights.
N140
-2°F ~ 80°F: 52fps
80°F ~ 165°F: 77fps
avg: 0.77fps per degree
Comments:
Not personally a fan of this powder as it pressures out early (in the 223 at least). Higher temp response than either of its faster siblings. It is said to be very accurate, but I'll never know as N135 gives me 0.25MOA accuracy and more velocity. Good SDs, outside of the very cold.
Benchmark
-8°F ~ 76°F: -8fps
76°F ~ 162°F: 12fps
avg: <0.1fps per degree
Comments:
Stupid, silly stable. Paradoxical temperature response. I tested Benchmark before and I know that its velocity continues to drop slightly even until around 116°F, before starting to rise again. IMR4166 and AR Comp (both double based) also exhibit similar behavior. Very tight SD regardless of temp. You could load this powder near the very top just before any pressure signs and never encounter any serious signs in the field—regarless of the conditions. Too bad the velocity plateaus shortly after you reach compression
----
Ways to improve this test
1) get a hold of a other single skin warmer and keep an additional batch of ammo around 110°F, as well as a second cooler...one with regular ice only to keep around 30°F and one with dry ice to keep around -15°F. Five data points per powder.
2) do it in a humidity controlled environment. The cold bullets get instantly covered in a layer of frost in the Florida humidity and the bolt is had to close. Not sure how it affects the results of the test.
3) get another gun so I can test another class of powders. I don't have many left in the 223, 308, 6.8spc and 6.5 grendel range.
Description of test:
I used three general temperature windows to test: one at ambient temperature, one at a very cold and the last at very hot. These would simulate hunting in the spring/fall, the winter, and the summer, the first round that's sitting the chamber and the follow up shots one would take.
Procedures:
I used a freezer gel pack which sat in the freezer all night with (3) of each unique cartridge nestled inside, folded up. The temperature dropped well below zero while in the freezer. This went into a plastic cooler with ice.
I used a pair of battery powered muscle warmers wrapped in Aluminum foil and insulated in a cotton cloth for the hot test. This was kept in an insulated lunch bag, and left on the entire test.
Temperature was taken continuously with a 3-way temperature probe (-4°F~536°F); a temp gun was used on the cold cartridges when the temperature was outside of the probe's range.
Bullet used was the 75gr ELD-M, 223 Remington LC brass, Fed 205M primers, and no crimp. Powders and charges are shown in the images. Each charge was about 0.2gr below book max for SAAMI 223 Remington (55,000psi) as per Hodgdon and Vihtavuori online reloading tools.
I shot a single fouling shot at room temp before I began a [cold -> ambient -> hot] shot string with the same powder. (3) shots were taken of each temperature type. Between strings I let the barrel cool with the aid of alcohol infused wipes. Temperature was taken for each temp type just before loading them. Rounds were fired as quickly as possible once they were loaded in the chamber. Temperatures and velocities were recorded, and graphed with an online tool. Hurray for technology...too bad it took me a while to find that would plot the data I needed without trying to get my credit card info.
Discussion
If I had to do this test over I would omit the crimp (as I did for the second test). This test verified to me that some powders respond pressure-wise more severely than others; all three ambient temp velocities should be more or less the same in the above test. Perhaps AR Comp would have been a bit more stable if it lacked a crimp here...? The dotted line represents what AR Comp's curve would look like if I had a more granular means of testing the temperature response.
>>>Redid test w/ AR Comp & LT-32<<<
Cartridge details: 60gr HH, LC brass, BR-4, 25.2gr AR Comp or 23.8gr LT-32, no crimp (this is important, as AR Comp is far more neck tension sensitive than other powders I've tested, and it is known that LT-32 is as well).
AR Comp (test #2)
Cold: 2.5°F, avg velocity 3237fps
Cold to Ambient change: -30fps, -0.87% change
Ambient: 71°F, avg velocity 3207fps
Ambient to Hot change: 28fps, 0.73% change
Hot: 154°F, avg velocity 3235fps
Notes: much more bowl shaped curve than before, as the crimp increased pressure which increased cold pressure. Pressure and velocity should actually drop the most by about 115° or so, before going back up where you see it at here. Overall, very good regardless of cold or hot, but still not as good as we saw with Benchmark. I figured if I can actually get BM up to pressure it would show more sensitivity than last time.
LT-32
Cold: 3°F, avg velocity 3127fps
Cold to Ambient change: 83fps, 2.65% change
Ambient: 72°F, avg velocity 3210fps
Ambient to Hot change: 94fps, 2.99% change
Hot: 156°F, avg velocity 3306fps
Notes: definitely not as stable as the older T-32 it was based off of. While it was said to be more stable than N133, this is not the case anymore; many of the old BR guys likely have huge stashes of the old N133 before VV made steps to improve temp stability. Other than the low ES at all temps, the velocity swings too much for my tastes. Also to note, was that even though the cold temp velocity was the lowest, it had pressure signs!
Discussion
As you can see, behavior here was typical for what is expected with smokeless powder. This time I will list each powder individually, their total ES and within temp brackets, as well as provide any relevant commentary.
A2460
-8°F ~ 77°F: 118fps
77°F ~ 164°F: 149fps
avg: 1.55fps per degree
Comments:
like A2230, this powders has been shifted to production in multiple countries and this has not been stable in regards to temperature response in the last decade or two. Production is now here in Florida by St. Mark's. Also like A2230, temperature response has suffered and is what you would expect of a stereotypic spherical powder, as well as it's SD. It may perform better in larger capacity cartridges, though.
A2520
-8°F ~ 77°F: 110fps
77°F ~ 164°F: 228fps
avg: 1.97fps per degree
Comments:
Well, what can I say. HUGE spreads. In this powders defense, there were no pressure signs at all it had low SD in the cold. As Western stated in their FAQ, generally within a given style of powder, the slower varieties are more temperature sensitive than the faster ones. A2230 only had a spread of 162fps across nearly the same temperature range.
N133
-4°F ~ 78°F: 48fps
77°F ~ 165°F: 61fps
avg: 0.64fps per degree
Comments:
SD is best at ambient temperatures, but is still better in the extreme heat than the cold. Better than the last two, even at its worst. Has a copper fouling eliminator...but so does X-terminator. I guess this is typical temperature response for a non-Extreme extruded powder. Apparently it's changes are very predictable and benchrest shooters can account for it like clockwork.
N135
-4°F ~79°F: 35fps
79°F ~ 166°F: 74fps
avg: 0.64fps per degree
Comments:
Less heat stable and more cold stable than its little sister, N133, but larger SDs. Both get excellent velocities with proper bullet weights.
N140
-2°F ~ 80°F: 52fps
80°F ~ 165°F: 77fps
avg: 0.77fps per degree
Comments:
Not personally a fan of this powder as it pressures out early (in the 223 at least). Higher temp response than either of its faster siblings. It is said to be very accurate, but I'll never know as N135 gives me 0.25MOA accuracy and more velocity. Good SDs, outside of the very cold.
Benchmark
-8°F ~ 76°F: -8fps
76°F ~ 162°F: 12fps
avg: <0.1fps per degree
Comments:
Stupid, silly stable. Paradoxical temperature response. I tested Benchmark before and I know that its velocity continues to drop slightly even until around 116°F, before starting to rise again. IMR4166 and AR Comp (both double based) also exhibit similar behavior. Very tight SD regardless of temp. You could load this powder near the very top just before any pressure signs and never encounter any serious signs in the field—regarless of the conditions. Too bad the velocity plateaus shortly after you reach compression
----
Ways to improve this test
1) get a hold of a other single skin warmer and keep an additional batch of ammo around 110°F, as well as a second cooler...one with regular ice only to keep around 30°F and one with dry ice to keep around -15°F. Five data points per powder.
2) do it in a humidity controlled environment. The cold bullets get instantly covered in a layer of frost in the Florida humidity and the bolt is had to close. Not sure how it affects the results of the test.
3) get another gun so I can test another class of powders. I don't have many left in the 223, 308, 6.8spc and 6.5 grendel range.
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