YO! Wampum,
Took a bit of digging to find my records.......... Here's what I did year's ago most probably when or before your favorite thing was a 'binky".
Intended use: Knocking the heads off of fools hens (Ruff Grouse to youn's guys)
270 Win
W-W cases
Most probably CCI Primers (mag or nonmag???)
Sierra 90 grain HP.
Orginal Douglas Barrel:
10 grains of Unique 2 shots 1556/1606 FPS MV
New Lilja Barrel:
7.6 grains of Unique 1200 FPS MV.
I'm thinking your ESs will be humongous unless you buffer the empty space with something. The only things I can think of that you shouldn't use are tomato paste or honey.
Now here's the story that goes with.
I kept a handful of these "squib" loads just for the fools hens that make a very good meal and are all over the place.
Back in the Navy days we used to get 5 days off in a row every 5 weeks. That time was spent up in the middle fork country around Shovel and Yellow Jacket creeks chasing the elk. After several years, I was stationed here for 4 hunting seasons

, and no elk and plenty of fools hens I came up with the squib load.
During those years I never saw an elk, except once. That once weaned me from squib loads. I now carry a flipper. Yep a sling shot for Ruff Grouse, try that back there

),
On one hunt after about 3 days of hiking and glassing I come to a little clearing covered by something like Mtn. Laural (??) . On my side of the claring was a couple of fools hens. I stood still for a long moment to ensure that it was only grouse and me in the local.
I eased out the regular round and eased in the squib load. Not as easy as one would thing with that Mauser action.
I held over the grouse's head the appropriate amount. The squib load went off at who knows what velocity but I did see the bird's head splatter in the scope.
At that same moment with the spent case in my hand, the grouse flopping around like a chicken with it's head chopped off I see about a half dozen tanasses busting through the trees on the other side of the clearing. That is the only time in 4 seasons I saw elk.
No more squib loads!!!!