748 temperature sensitivity.

[garryc]

I understand extreme heat in some parts of the country. In my area mid 90's are considered blistering hot. Summer time comes in at high 80's to low 90's typically. So is that in the range that I need to worry about temperature sensitivity with 748?

The load has been 27 grains behind a 55 grain bullet in 223 with a standard primer or a Wolf 5.56. I hear that 26.5 gets around issues, What about 27 in your experience?

 

[rg1]

Just my experience with Win 748, 55 grain bullets, in .223 Rem in summertime temps. I worked up loads in the 27gr. plus range for mostly AR-15's but also for a bolt action Remington rifle. Most of my shooting occurs in the spring and fall or winter. Never had an issue until shooting one day in 95 degrees, ammo had been in ammo cans in a car but not extremely hot inside the car. Shot the 27 gr. plus in my bolt action and had very scary high pressure signs. I trust Win 748 with 55 gr. bullets at some recommended maximums at 26.4-26.5 grains. I don't trust higher load levels in extreme heat. Either ammo in a hot car, sitting in the sun, or a round left in a hot chamber long enough to soak up the heat. I've since tested 26.4 grains of Win 748 in AR's and bolt actions in hot temperatures and no issues. Not saying that Win 748 is the only powder that's sensitive to heat but it does have a reputation of being heat sensitive. Surprising but 26.4 is also my most accurate load.

 

[Ifishsum]

Only time I noticed was near max loads, a very hot day and the box had been in the sun for a while. Didn't even think of it until later, seeing very flattened/cratered primers. I don't think normal ambient temps are a whole lot to worry about unless you're pushing the max. Sitting in a hot car, direct sun or a hot chamber goes a lot further than normal IMO.

 

[Road_Clam]

W748 is my go to powder for versatility. My 308 loads and my AR15 shoot fantastic with W748. I do observe some "instability" but many people over rate it. Ive done all my chrono testing in both fall colder temps and summer warmth. A typical scenario is :

50F I will load 42.2 gr

80F I will load 41.8 gr.

Velocities both remain around 2540 fps. out of my 26" bbl with a 168 gr match bullet.