I shot some more 338LM today, and among other powders I tested some more Retumbo.
I have become a bit more accustomed to the Savage 110BA's idiosyncracies... what is purported to be a "state of the art" stock is not honestly to my liking, it's too "AR-ish" to suit me.
But it does work, when you get used to it.
My preference is for the center of gravity on the rifle to remain as close to the bore-line as possible. With the AR type pistol grip stock, I find that the heavy rifle (it weighs about 20 pounds scoped and prepped) wants to toggle left to right, seeming top heavy, in my opinion.
This top heaviness, combined with a Harris "S" bi-pod, (which allows the rifle to rotate clockwise and counter-clockwise in the bi-pod saddle) makes it feel unstable when shooting off the bi-pod and rear bag. The rifle seemed to want to topple left or right.
I installed a bi-pod locking lever, which replaces the knurled screw that comes on the Harris S, and situated that lever to really tighten
the bi-pod down. This way it doesn't swivel at all... without the pod lock, you can't really get the knurled knob tight enough to stop the rotating of the rifle.
So I would highly recommend the pod lock lever if you're using a Harris S model bi-pod.
You will also want the Harris model with the notched legs, instead of the legs that you have to tighten the knurled knob down to hold them where you want them. This rifle is too heavy for you be able to count on those legs not collapsing in, to some degree, either on recoil or as you're preparing for the shot.
I think the non-swiveling (not the S model) bi-pod with the notched legs might be the best option for the rifle.
We know that for every action there is an equal and opposite reaction. For the action of a 300 grain bullet speeding down a 9 twist .338 inch bore at 2700 fps, the reaction is for that bullet, *to some measurable degree
* to turn the rifle in the direction of the twist. If you don't have the rifle stabilized against rotating (as is the case with the S bi-pod), you're going to get poor accuracy and a wandering POI. Ask me how I know... I found this out through trial and error, never having had a rifle that wanted to do this sort of thing.
But lock that bi-pod TIGHT against letting the rifle rotate and accuracy is greatly improved, and POI stays where it should.
Here is a target I shot today at 105 yards, using the OCW of 89.3 grains of Retumbo, Lapua cases, CCI 250's, at 3.690" total OAL. Cold clean bore and four follow up shots...
The CCB shot was around 2680 fps, while the next four shots were all within 5 fps of 2700 fps. This load is going to work.
Cold clean bore shot to right, other four shots in the oblong hole in box.
The Retumbo, like all the other Hodgdon extreme rated powders I've worked with, really wants maximum load density. I think the coating they use to make the powder more temperature stable also makes the charge harder to light than with conventional powders--so you need a large enough charge to make sure it can't pour forward, away from the primer flash, perhaps making ignition inconsistent.
The next higher node with this powder and bullet combo is at 92 grains, but I had flat primers and ejector swipes at that level. At 89.3, all seems well and good.