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/

Six of the models tested were binoculars, and the other two were monoculars. The Leupold monocular was included for reference, because many shooters have a 1,000-yard rangefinder similar to the RX-1000. The Vectronix Terrapin model was included as the control for ranging performance, because it is known to be an extremely accurate rangefinder (spoiler alert: it is). Cal provides a very detailed side-by-side spec comparison for these models in one of his posts.

Ranging Test Results

Each model was used to range 500+ times in a variety of scenarios from 25 to over 30,000 yards. The tests showed these models had similar performance at close and mid-range targets, but at 600 yards their performance started to diverge … so that is where most of the testing was focused.

The chart below summarizes the ranging performance found on the test targets in ideal conditions, which was from a sturdy tripod, at sunset, with 10+ mile visibility. The exact target shape and surroundings varied, but the targets were all approximately 2 MOA wide, highly reflective, and perpendicular to the rangefinder. Specifics on target dimensions, view from the ranging position, and target surroundings are given in the detailed ranging performance results post.

Vectronix is the leader of the rangefinder world, and that was proved once again in these tests. The new Leica Geovid HD-B wasn’t far behind them, with accurate ranging beyond 1 mile. The Zeiss Victory RF also had surgical precision off a tripod, although it had a reduced range compared to the Vectronix and Leica. The Bushnell Fusion 1 Mile also proved to be able to range targets out to their claimed max range of 1,760 yards.

PrecisionRifleBlog.com also tested the ranging performance of each model in bright lighting conditions, and offhand as well. The data from those tests also contained a few surprises. To determine how accurate each model really was, Cal Zant carefully analyzed the results from each model when aimed at precisely positioned, “known distance” targets. To see how those tests turned out, or learn more details about specific models, GO TO full results.

Optical Test Results

For the optics tests, Cal’s goal was to find an objective, data-driven approach to testing optical performance. What he came up with was placing eye exam charts from 600 to 1,400 yards with different size letters, and then recording what two different people could accurately read with each model. The data for each unit was summed into a single score so they could be ranked relative to how much detail the testers could make out. More specifics are provided regarding how the test was conducted and how scores were calculated in the optical performance results post. Here are the results from Cal’s data-driven approach:

The Leica Geovid HD-B edged out the other models for the top spot, with its completely new, Perger-Porro prism design. The original Leica Geovid HD, and Zeiss Victory RF also showed great optical clarity.

The Rest of the Story

Cal’s full series of posts is very informative. He’s done tons of analysis on the data, and summarizes it in several charts that provide a lot of insight. Cal is also in the process of publishing detailed reviews on each model, including notes he and the other testers compiled for each unit. They used them all — a lot, so they have a unique perspective on what’s good or bad about each. Find out more at the link below:

CLICK HERE to Read Full Article with More Info