Home Forums Hunting & Shooting Ask The Gunwriters Temperature Insensitve Powder for 7mm Remington Magnum

Well, time for some input here that contradicts what has been posted.

I shoot both rifles and shotguns competitively. From very recent experience (Sunday), I can say for certainty that H-4350 is not temperature insensitive as is claimed.

I shoot a 6.5 Creedmoor with 41.3 grains of H-4350. I've been using the same lot of powder since the warmer Summer months. Just last week I checked long range data by shooting. The data had not changed. Temperature was 57 degrees and was entered into Ballistic AE along with the other atmospheric data.

On Sunday we had our little local Precision Match. It was very cold all day with the temperature from 36 degrees to 41 degrees at the end of the match. When targets were engaged at 760 yards, impacts were .2 Mils low. I thought my zero was off, not the drop data, so I added .2 mils to my zero.

Had many chances to check the 100 yard zero as we shoot paper during the match. Well, it was now .2 mils too high. I moved it back to the original zero. As long range targets were engaged, everything was low. I can only attribute the change in drop data to the cold temperatures decreasing velocity.

Ballistic AE has a "temperature sensitivity" parameter in the rifle profile reloading set up page where a number can be input as a decrease/increase in velocity per degree of temperature change. I had never used this part of the program. I entered "3" as in 3 fps change per degree of temperature and the output matched my actual for Sunday's shoot at the colder temperature. The temperature at the time of load development was 55 degrees giving a velocity of 2785 fps. After the conditions on Sunday were input with the Sensitivity feature enabled, the program output that the velocity was now 2743 fps and gave proper data for drop.

With H-4350's reputation as very insensitive to temperature, I was very surprised to see this. I also now believe that ALL powders have to be sensitive to temperature changes.

rcamuglia,

I would contact Hodgdon and tell them your H4350 experience. Your lot of powder might be defective.

I've talked to a few powder manufacturers, and while they won't tell any journalist everything (for obvious reasons in a very competitive business), but they have admitted that lot-to-lot uniformity of any powder is difficult, mostly due to differences in atmospheric moisture.

My last test with H4350 was with a 7x57 and 140-grain bullets. I run my cold-change tests by chronographing on different days, one as close to 70 as possible and the other as close to zero as possible. The rifle and ammo are at the same temperature as the air (for the cold tests I leave them in an unheated garage overnight), and the same chronograph is used. I also run point-of-impact tests at the same time. At 70 degrees the load chronographed 2842 fps, at zero 2834, which is as little (or even less) variation than usually occurs between shot strings on the same day.

That test just confirmed a LOT of chronographing of H4350 loads I've done in varying conditions over the years. I certainly wouldn't expect the difference you encountered, which is why I suggest contacting Hodgdon.

Another great reason to buy powder by the 8# keg...

What if the 8# keg is defective? Then you're stuck with 7.9# of defective powder...