I’ve been working up a load for 6.5 Creed. I’m using Ramshot Big Game. When I first shot it, it was very consistent. I started low, going up .2 grains. It did exactly what I would expect, and ended up about 2800 fps.

So I loaded up some more. 10 with 41.0 grains, 10 with 41.5, and 10 with 42.0.

I shot the first 20 last week and it was very consistent. The 41.0 grains had a speed difference of 38 fps between lowest and highest. The 41.5 had a difference of 51 fps between lowest and highest (but 7 of those were within 10 fps of each other).

Today I shot the 42.0 grain loads and they were 200-300 fps slower! With a bigger swing (just under 100 fps between lowest and highest) WTF? It was colder today, but only by about 20 degrees. Last week was upper 80s, and this morning was upper 60s.

Do you think the temperature could be the cause? Or possibly I’m getting too close to max load? From one website, I’m .6 under max, and from manufacturer I think I was something like 1.3 under max.

Any thoughts?

Ramshot is allegedly temperature sensitive, but not to the extent you're seeing.

https://ramshot.com/faq/#:~:te...hunting%20conditions.

Most of our powders are not insensitive, and will show some effect at hot and cold temperatures.

However, we test at -40F and +125F and the deviation in most cases are ca 3% to 5% at these extreme levels. Therefore most shooters do not notice much difference under normal practical hunting conditions.