Gryphon - the .358 Norma is quite a straight sided case to start with & already has a short neck & good shoulder angle. Improving it probalb won't give 6gr. difference and that might give 0 to 50fps increase in speed. I don't think there would be anything close to 100fps improvement if improving it in standard form (I don't think there is a registered .358 Norma Ackley Improved Magnum ctg.) but anything is possible becasue anyone can have the reamer made & then cut a chamber with it. Like Gatsby said, the .358 Ackley Magnum is virtually identical, ballistically and load for load to the .358 Norma.

The ctg.s that give big improvements after improving were originally slightly underloaded and had quite tapered cases. After improving, they were loaded up to the capability of the ctg. in strong actions and showed wonderful improvements. Examples would be the .250 Savage and .257 Roberts. Others would be the wonderful improvements found between factory .35 Whelen and what the Whelen Improved round provides. More, are the .348 Winchester and the Improved versions along with a .375/06IMP compared to a standard .375/06. When you increase the shoulder .020" and increase the body length by 1/10", along with an increase in head to .470", you end up with an 80 gr. capacity case. In .35, that would be the Brown Whelen, which duplicated or came close to duplicating the .35 Norma Mag. Th is surely shows that for efficiency, Ackley was right - the Norma case is about at the top for efficiency. This doesn't mean you can't increase the speed, though. If you are willing to put a large enough case behind it and burn the powder with attendent bore and throat errosion, you can. Why, you can even get a 110gr. capacity case in .308 calibre now. The .50 BMG case will give a .30 even higher speeds. There might be an upper limit, though - with the 20mm case.

The .358 STW is like gatsby says - way to much powder for that bore size, with normal weight bullets, at least.

The .358 Norma will do close to 2,900fps (maybe over) with a 250gr. and top handloads with today's powders. It's been 35 years since I owned one & my memory's a bit foggy.

I can't see there being a need for more than that, but then, each to his own - my needs are not the same as someone elses - that's what's special about living in a free country. You can have whatever you want or can dream up. Remington did - HA! I have 3 or 4 I dreamed up that no one else seems to want -

HA!). such is life