Interesting results. Hodgdon manual for 90grain bullet is 38.0 to 40.5. I started at 36.1 and went up in steps of 1% more powder (0.3 to 0.4 grains). Bullet is Nosler 90 BT seated at 0.023" off jam - length base to ogive of 2.390" using Hornady comparator
#1 H380 36.1 2894 fps
#2 " " 36.4 2905
#3 " " 36.8 2929
#4 " " 37.2 2964
#4 reached clear signs of pressure - flattened primer and bolt was sticky to open. I quit at that point. 37.2 is way below Hodgdon upper limit of 40.0. Is that because I am running my bullet seated longer than their factory standard?
I suppose I will load up a few more at steps going down from 36.1 to see what the results are and will call 36.8 max. I don't see much need to load it that hot though since 1,2 and 3 were all within 35 fps.
Thoughts?
where you were seeing pressure signs, try seating the bullet a little deeper, like a 1/4 turn only on the seating die...see what that tells you...
H 380 is slower than 4064, and I can run 40 grains of IMR 4064 ALL DAY and not see pressure signs with a 90 grain bullet, to include Ballistic Tip ( as I shoot a lot of those and 95 grainers also )
You didn't mention outside temps, but I don't think that is coming into play this time of the year, except maybe down on the southern border states still...
Even tho it is commonly said to use Larger Rifle Mag primers with H 380, I've gotten along fine for decades with regular large rifle primers.
H 380 has been able to shoot 90 grain bullets at 3150 fps, with no issues in the 5 or 6 243s in the gun cabinet. Ruger, Winchester Model 70, Remington 700, and Savage Model 10.
