Home Forums Reloading Big Game Rifles w760/h414 how temp sensitive is it ?

w760 shoots any bullet from 120 to 150 grains faster in my 7mm-08 than any thing else i have tried . Have tried it against h and imr 4350, varget and rl19. I have checked loads worked up in the hot summer again on 70 degree days and was losing around 80 fps .which i know is no big deal but was wondering if it will continue to loose velocity as the weather turns colder ? I havent noticed a change in poi , but i dont spend much time on the range once i begin hunting .

I can't answer your question except to say that I've probably killed more caribou with 760/414 than anything else. I tend to work up in warm weather: 50s, and hunt in weather 40-80� colder. That has always worked for me.

Most of my load work up has been done in my local summer heat at 100 plus degrees in temperatue. They've worked just in it tnear freezing to 70 drgree temps depending where I'm hunting in Arizona.
Paul B.

I have used w760but it is in my opinion very temp sensitive, so much so that I no longer use it. I live in Canada and loads worked up in summer ie 85 degrees farenheight show significantly less pressure and groups open up at the temperatures we hunt at. ie -15F. This could be compensated for by adding two or three grains for cold weather and retesting but if those shells were used in hot weather they would be way over pressure.

Thanks for that info.
I use a lot of H-414 and am interested in your findings.

First time I used W760 I got things backwards. I worked up a load in January instead of closer to the summer. Things worked out great for a February javelina hunt, but when I shot the load at the range in June, I blew a primer. That was the first time this had happened to me (and it hasn't happened since), so I vowed to not use the powder again. Going back through my notes though, nothing so far gives a better combination of accuracy and velocity in my 7x57 with bullets over 145 grains. So, next time I load heavier bullets I'm going to give it a try again. Like others, I'll load in whether as warm as I'll likely hunt, then see what happenes to my accuracy once temps get cooler.

I have chronographed tests with loads worked up in the Australian heat then chronographed them in several rifles in the Rockies at about 20 degrees and found very little difference and no change in POI for any of the loads tested.

Because others have found variance, I would conclude that there could possibly be a lot to lot variance in performance. Whether it is enough of concern is something you need to evaluate yourself as the hunting conditions, temperatures and altitudes can only be influenced by the user.

JW

I used 760 in a 17Rem years ago. Worked up the load with 25gr Bergers in March when temps were 30 degrees. Then, in June in So.Dakota with temps in the 80-90's, the Bergers were vaporizing and primers were blowing out! Went back to IMR4320 and didn't have any problems.

With all that said, I still use 760 in my 22-250 but only in the winter for 'yotes.

WN

The temperature stability of 760/414 may be cartridge dependent. I believe Denton Bramwell has shown Varget to be affected this way.

A lab tech at one of the major pressure laboratories told me the same thing about Varget. His comment, however, was that when it was "stressed" it lost some of it's temp-resistance. The example he used was Varget loaded to top pressures in the .260 Remington with 140-grain bullets, a place where something slower would work.

One of the points he made was that how much TIME it takes to reach peak pressure has a real effect on temp-sensitivity. He really likes to find a powder that reaches optimimum (not necessarily maximum) pressures just about the time the charge fills the case 100% or a little more. This not only produces a pressure curve that doesn't rise too steeply, but more uniform velocities.

That said, some powders are more temp-sensitive than others, even when used with the "correct" case and bullet.

There have been enough varying opinions that the chrono information is welcome to me. I have 2 rifles that really like 414. The consistency has been the only real question for me.

I've used H414 for at least twenty years in a number of cartridges. I suspect the temperature sensitivity aspect may have been exaggerated but there is (or was) more lot-to-lot variation than with other powders. Book velocity and my chronographed data sometimes showed wide discrepancies. However, I've yet to find a more accurate powder for use in the .22-250 and the Swift. The last such loads I chronographed two or three years ago were pretty much in agreement with book figures.

An interesting side point here is, I tested loads using H-414, then substituted 760(same powder weight/same bullet/same primer in 7x57's), and there was a significant difference in accuracy. So, I concluded that different lots of either H-414 and 760 "may" deliver different accuracy. I test accuracy when changing lots of either powder.

A couple of decades ago I shot some 400 bullets with 760 in a .416 Howell. Cartridges from the same box averaged 2410fps at 80 degrees and 2310fps at 45 degrees.

Walt

I have always found H414 just a touch slower than 740. I was shocked to find out that it was the same powder.

It maybe like Winchester 296 and Winchester 295(H110), one just a tad off from the the other.

No, they are the same powder, as are H110 and 296. You probably just had different lots.

Since Hodgdon bought the rights to the Winchester powders they have been publishing identical data for 414/760 and 110/296.

Let me qualify this a little.
When I chronographed 7 or 8 rifles in varying calibers between the 2 countries with commensurate varying conditions, the total valiance of all cartridges was something less than 120fps. Many loads were within 10-20fps which is normal shot to shot varieance.

Coming from a relatively hot climate compared to the US, I was not qualified to comment on the variance you people have reported so my own records are exactly that.

JW

Now that you mention it, I did have the same problem substituting 296 for H-110 in a 22 Hornet. Same powder weight, same bullet seated the same way and same primers, I got great accuracy with the H-110, and bad accuracy with the 296.

Edit to add: Great accuracy mentioned above was 3 shots at 100 yards into groups measuring 1/2" to 3/4", while bad accuracy was 1 1/2" to 2" at 100.