Powder Temp Stability: IMR Enduron vs. Hodgdon Extreme
PrecisionRifleBlog.com (PRB) recently published results from a field test PRB conducted to quantify the temperature stability of the popular Hodgdon H4350 and Varget powders and compare those to IMR’s new Enduron line of powders, specifically IMR 4166 and 4451.
Hodgdon Extreme Series powders have attracted quite a fan base, with over 90% of the top shooters in the Precision Rifle Series choosing to run one of those powders. IMR recently released a new line of powders “with Enduron Technology” — which is also marketed to have “extreme temperature stability”. Sounds familiar! These new powders should compete directly with the Hodgdon Extreme Series, which gives shooters more temp-stable powder options to consider.
CLICK HERE to Read Full Powder Temperature Stability Test on Precision RifleBlog.com.
The top shooters in the PRS and veteran long-range shooters in other disciplines have learned to value a temperature-stable powder. That’s because a change in temperature can affect the trajectory or “flight path” of the bullet in two well-known ways:
1. Assuming all other environmental conditions remain the same, an increase in air temperature will cause a flatter trajectory due to a lower air density (easier for the bullet to cut through the air).
2. The same increase in temperature also causes the nitrocellulose-based powder inside the cartridge to burn at a higher rate, producing approximately four times the Point of Impact (POI) shift than just air temperature alone. (SEE: Temperature Effects On Zero on KestrelMeters.com.)
“The initial heat condition of your powder will affect the burn rate,” Bryan Litz explained at a recent Applied Ballistics Seminar. That means swings in ambient outside temperature can affect your internal ballistics, which will directly affect your muzzle velocity, which will change your bullet’s trajectory. Some powders are more affected by changes in temperature than others. So if your goal is first-shot hits and you may shoot in a variety of conditions — you should care about temperature stable powders.
The folks at PrecisionRifleBlog.com meticulously loaded 6.5×47 Lapua ammo with each powder using some of the best equipment available. This included the top-of-the-line Prometheus Gen II Powder Scale, which is capable of loading to the nearest kernel of powder. This ensured the powder charges were identical for each round of ammo. PRB’s testers explain the full set of equipment and steps in their loading process in the Full Test Report.
Once they had a couple dozen rounds loaded with each powder, they went and shot them with each powder at 25° F, 65° F, and 140° F. The muzzle velocity of each shot was recorded using both a LabRadar Doppler Radar and a MagnetoSpeed Chronograph. The LabRadar is a new type of device that allows you to measure muzzle velocity within at least +/- 0.1% of the reading.
Here are the results from the PRB Powder Temp Stability Tests:
You can see Hodgdon H4350 had the least variance in muzzle velocity, with just 25 fps over the 115° swing in temperature! That is very, very low. Hodgdon Varget was the second least temperature sensitive powder in this test, with 46 fps of variance in muzzle velocity between temperatures of 25° F and 140° F. IMR 4166 performed very similar to Varget, and proved to be fairly insensitive to large swings in temperature. IMR 4451 had the largest swing in muzzle velocity of the powders tested, but keep in mind just 68 fps over 115° F swing is still a good performance.
Most powders aren’t specially formulated to be temperature stable. So they would likely show much larger swings than what these four top-performing powders showed.
PRB’s test team also noticed other interesting trends in the data. For example, variation in velocity does NOT appear to be linear across the full range of temperatures. By that, they mean the change per degree from 20° to 65° might be smaller or larger than the change per degree from 65° to 140°.
PRB’s testers talk about those things, provide a few other insightful views of the data, and discuss tools that can help you manage temp/muzzle velocity in the field in their full post. You can find that here: http://precisionrifleblog.com/2016/06/19/powder-temp-stability-hodgdon-extreme-vs-imr-enduron/
Similar Posts:
- Powder Temp Stability — IMR Enduron vs. H4350 and Varget
- Smarter Shooter: Keep Your Ammo Cool on Hot Summer Days
- Effects of Heat on Powder Performance
- Beat the Heat: Keep Your Ammo Cool in Summer
- Don’t Roast Your Ammo — Watch Temps in Hot Summer Months
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Tags: 6.5x47 Lapua, Cal Zant, Enduron, H4350, IMR 4166, IMR 4451, PRB, Precision Rifle Blog, PrecisionRifleBlog.com, Prometheus, Temperature Stability, Varget
Did you test the powder at 100 F. I have shot matches at 100 F not 140.
Since you said what I have belived that the velocity variations are not linear
with temp, the change in velocity per 1 degree temp are not accurate.
Tibosresrex on Sniper 101 has been preaching that powder performance does not change in a liner fashion for over a decade.
I do not care about impact. I do care about barrel tuning, so will stick to 4350.
I really would like to see the data for all temps. Then I could adjust the data to simulate where I’m shooting and the season. This would be a worthwhile consideration and would allow one to make a powder selection based on the best performing powder at various ambient temp.
Additionally one could consider the impact on chamber temp when shooting a string at those temps.
What Jim Miller said …
I wouldn’t call 68 fps non-temp sensitive. Your not going to see numbers much higher from any powder.
Beside the POI change, why is this so important? And even then lets say 260 rem 2850 and 2925 fps at 600 meters it makes for a .8 moa change on my setup witch is about 4.8 inch. that is over a string of fire … not from shot to shot btw.. And I should change the load that perform for me because of that? My argument is that is more marketing than anything else. If you are not convinced of what I say there is a well known video of demonstration 800 yard F-class on YT often on this site too, where the shooter makes changes withing is shooting string of multiple clicks up and down…. temps sensitive powder?