Ran into a unique mold
Ideal # 269386 designed for the 256 Newton
which surprisingly was a 6.5 mm bullet on a necked down 30-06 case
Working up loads to about 1950 FPS with H380
results after range day

I did not know a mold existed for the Newton. I know a guy who loves the caliber and has an extremely nice hunting rifle for it he breaks out to hunt the occasional Pronghorn. IIRC, his was made in 1916. He has very few bullets left and he is always on the hunt for more "NOS" cartridges. I'll pass along this mold # and see if he has it.

I know the Newtons had pretty strange "segmented parabolic rifling". Rather unique.

-DallanC

so the Newton isnt a 6.5/06??? as we know it???

It is, but not literally.
The .256 Newton and 6.5-06 are very similar 6.5mm cartridges based on the .30-06 case, offering nearly identical ballistic performance, though they are not directly interchangeable. The .256 Newton (introduced 1913) features a sharper 23-degree shoulder, more body taper, and a shorter case than the 6.5-06. The 6.5-06 is a popular "wildcat" (no standardized factory load for many years).
The .256 Newton is essentially an early, proprietary version of the 6.5-06 wildcat. The 6.5-06 is more common today, particularly in custom builds using modern powders, but both function as high-velocity, medium-game cartridges.
cited from AI Overview
I am applying it's design for a Grendel, not an "06
my concern is keeping my bullet from leading the barrel and consistant POI

I'm not constrained to OAL of AR mags as I shoot the Grendel in a contender and an encore, 16 and 24 inch barrels respectively
Modern bullet designs use a much different ogive and allow a projectile to protrude much deeper into the bore.
The cast bullet I'm working with is shorter and stubbier and engages the rifling when seated out any further.

gemihur wrote:

my concern is keeping my bullet from leading the barrel and consistant POI

After reading a few posts in The Nut in relation to bullet lubing and leading…give consideration to powder coating your bullets. Also choose the hardness of your bullet carefully. I’m surprised these bullets aren’t gas checked.

I use an alloy of 6/2/92 (92% Pb lead, 6% Sb antimony, 2% Sn tin) this is about 16 BHN hard (maybe a bit soft for hi power loads), otherwise Lyman #2 is 90% Pb lead, 5% Sb antimony, 5% Sn tin at around 25 BHN…a bit harder. Maybe using pure Linotype (Linotype metal typically consists of 84% lead, 4% tin, and 12% antimony, producing a high Brinell Hardness (BHN) of approximately 22), a little softer than Lyman #2. Whichever way, you should be able to produce a very good and capable cast bullet.