Actually.I made theassumption that the T/C was a break actionsingle shot,and that was the reasoning.
I think I saw an ad showing the Icon as a bolt gun.In that case,if its a front locking lug action,spring is not likely.
The Whelen does not have much shoulder,and it is a fairly shallow angle.
I assume you are carefully setting your sizing die for about .002 head clearance.
What sort of extractor setup does it have?I ask because the .012 or so thick brass at the shoulder just is not very strong.If the extractor is a snap over the rim type,closing the bolt may be setting the shoulder back.You could check that with a before/after check cycling ammo without shooting.
You have rejected improved versions.They would provide a better shoulder,but I'll respect your choice.
The small,shallow shoulders on the H+H cartridges inspired the belt,for exactly the ignition problems you describe.A good anvil!
Back in the Milsurp Sporter heyday,Norma had a deal going to rent the Norma mag reamers to smiths.Selling ammo and brass was the plan.I think maybe,back then,Schultz and Larson was the only factory chambered rifle.
Springfields,P-17 and P-14 Enfields,M-70's,etc were converted
Without arguing whether it was a good idea,older bro had a .358 Win fwt pre-64 M-70 converted to .358 Norma.(Remember,in 1964 a pre-64 was the common rack M-70,and .358 Win,great cartridge it was,was an orphan.Bro was making trips to Canada for moose,)
It was quite a rifle.