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

7828 is all i shoot

I like RL22 and most recently have been having exceptional accuracy with H1000. Burns very clean too. I also have had good luck with RL19 and 140 NBT's. I've not noticed any temp. problems with RL powders but don't shoot/hunt much when it's hot either.

It's my thought that IMR 7828 was developed especially for the 7RM. Anyone out there no for sure?

JB can tell us for sure I'd bet but that's the rumor I'd always heard as well.

Dober

My experience with 7828...

I had to back off a load that was developed in sud 60 degree temps by a full grain when temps reached over 80 degrees. Loads were for a .300 Weatherby using 180gr Partitions.

My accuracy loads for a couple of 7RMs have been with 7828.

I had always heard that IMR7828 was Winchester's choice for the .264 Mangleum. It's one of the VERY few times a canister powder was used for a factory load.

On so-called temperature insensitive powders, there are so many "yes but" and "only if" and "except when" disclaimers attached to them that I treat such advertising claims as essentially meaningless.

aj300mag-do you recall what the speed was of the load and how many grains of 7828 you were running? Also, was it from the same lot?

I'd bet that the 60 degree load was running on the edge and the xtra 20 put it over. Maybe...?

Thx
Dober

I pulled a factory 140 power point a few years ago, it looks like they switched to some sort of ball powder that looked a lot like 780

I'd heard that, but have never dissected a factory round of .264. That's why I used the past tense.

Sorry for the temporary thread derail.

Not a 7mm. but have loaded RL-22 in the .300 Win. A perfect match with 180's most of the time. I have chronographed RL-22 from the mid ninety degress to 23 degrees and it lost right at 2 feet per second per degree of temperature reduction. I have found that different lots can vary, sometimes quite a bit. Though I don't get the high velocities that can be attained with RL-22, I have found that the Hodgdon Extremes seem to be much more consistant. Maybe, if using RL-22, buy a 5 pound jug and develope a summer and winter load ?
FWIW,
Jim

Mark IIRC when I originally worked up the load in cool weather I had backed off a load that had a stiff bolt by 1/2 grain. That load (I settled on) was one grain below the max load listed in the Nosler manual. Once the temps here reached 80 degrees that load brought back the stiff bolt on opening and the primer pockets were taking a pounding. Velocity was in the 3150fps range.

All loads were with the same lot number.

I've also had excellent results using IMR4831 in the 7mmRM.

Thx AJ-this is just me and not trying to rebuke or anything but if the bolts a bit stiff in cold weather then it's a safe bet that as it warms up it's definately gonna be hot.

Reducing it by 1/2 grain to me would mean something in a small case like a 223 or 17 Rem but in a big jug like the 300 Wby it's not gonna be enough. I'd say something along the lines of 1-2 grains was more along the lines of what was needed but that's just a swag.

Thx for the nice discussion.

Dober

I've done lots of handloading for 7mm's - mostly 7RM and 7WSM's. Were it me, I'd concentrate on H4831 with 140/150 gr pills and Magnum for 160's. H 4831 will work with the 160's, in fact has shot some of the smallest groups, but Magnum will get almost as small of groups but give 75-100 ft/sec more velocity. 72.0 gr Magnum in my current 24" 7WSM under a 160 Partition gets 3050 with sub MOA groups. 63.5 of H4831 under the same bullet nets 2950 and sub MOA.

I've had really good luck with IMR 7828 and Re 22 as well - but acheive the same thing with H4831 and Magnum so have switched to them and don't worry about temps.

Jack O'Connor wrote that in one of his books.

I know they're using canister 780 in at least one factory load these days.

I pulled a Winchester Supreme .270 Win 140gr Accubond (because they shot so dang good in my rifle). There was a ball powder in it that weighed 57.5gr. Hodgdon data listed 58gr as max with a 140gr Swift, so I bought a pound of 780 and worked up a load with Accubonds. Sure enough, when I got to 57.5gr, it clocked the exact same speed as the Winchester Supreme factory loads, so it appears to be canister powder in that load at least.

Thanks Mark. Your feedback is always greatly appreciated! I know you fall into the BTDT category...

Once again, the reason I prefer the term temperature resistant because there is no truly temperature-proof powder--yet.

The powders that have done best in my own tests have all essentially chronographed the same at zero and 70 Fahrenheit. Not many powders do that, but some do, notably all the Hodgdon Extremes I've tested, plus Ramshot TAC and Big Game.

But even all those powders tend to increase in velocity at temperatures over 70. The increase isn't as much as with standard powders, often only half as much. But apparently no powder company so far has figured out how to produce powders that are velocity (and hence pressure) stable in temmperatures over 70.

Some powders aren't quite as temp-stable as those I just listed bit better than average. In that class I'd put Reloder 15, plus Ramshot Hunter and Magnum.

The claims for temp-resistance aren't BS, as some have suggested, but there are limitations to the technology powder manufacturers now have. Plus, sometimes other variables will affect even the most temp-resistant powders. A ballistic lab tech (who has done a lot more temp-testing than I have) once explained that stressing a powder doesn't help its temp-resistance.

By this he meant using it for less than ideal purposes What he calls ideal is a load that fills the case and produces about all the velocity a certain case and bullet weight are capable of, at safe pressures. The example he gave of a stressed powder is Varget and a 140-grain bullet in the .260 Remington. While accuracy might be good, the powder charge won't fill the case or produce top velocities--and Varget won't be nearly as temp-resistant as it would be with a lighter bullet, or H4350 would be with a 140.

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.

I've had that same experience with RL 22 in a .30-06 Imp. Scared the Schitt outta me. Haven't used '22 since.

IIRC, the Sierra Manual ran some tests on temp sensitivity. They ran a couple of different IMR powders.

It ran 2 fps/deg F. So, a 100 deg diff is 200 fps and a 50 deg diff is 100 fps. I can see 200 fps throwing things off a bit at a fair distance.