Why is 35 Whelen pressure at 58k and 338-06 at 65k ??

I am assuming its because the whelen is an old wildcat and older rifles may be chambered for it ??

But then again it was legitimized in 1987 which is not that old but the 338-06 has
been around a long time too in wildcat form.

You got it right - older cartridge and a larger, more conservative company (Remington) made the 35 a "legit" cartridge while a smaller, less conservative company (A-Square) did the 338.

You know anybody loading the 180 gr barnes tipped TSX in 35 whelen.

Trying to figure out how much I can push it.
Double tap has a load with that bullet at 3000 fps but no telling what barrel length.
I am sure I could moly it and or AI the chamber and get there oe beyond.

Loaddata has a load for the old coated 180 gr X bullet running at 3095.

For now looking for flat shooting 358 load good out to 400 yards that makes a big hole which is what I am after
for this particular load. Will get to the heavy loads later.

Also weighing the 35 Whelen against the 338-06 loaded with a 185 gr tipped TSX. Its slightly flatter shooting out to 400 but not by much.
Maybe 2-3" at 400yds.

This will be mostly a large hog slammer.

It is because Remington chambered it in thier 7400 auto loader and 7600 pump. Same fate fell on the 280 Express. Which is now the 280 Remington. I have a US Model 1917 (95 years old) and the rifle was built 30 years ago before Remington made it standard. My loads are up there at 60,000psi and I could go farther except the case runs out of space. I should have had it chambered for the Brown Whelen Improved. My current load is 59gr of 4895 Russian and a 200 gr Hornaday Spire Point. Case is made from Remington 3006 brass. I am running a standard Remington LRP, 2700fps 22fps extreme spread (22 inch barrel). Five rounds at my 125 yard range prints a .625 to .750 group consistently My other load is 58grs of the same powder and a Hornaday 250 round nose everything else is the same 2400fps and 12fps extreme spread. Groups as good as the lighter round and it hits like a Howitzer!
Best regards,
Grit