I have 338-378 Norma brass that's been loaded 5 times with no lose pockets. I full length resize and load 285 grn bullets on the high end. I think the brass gets a bad wrap with those that have not used it a lot or possibly really push it. I can't ask for much more tan 6 loads although we will see how any more I get. As for accuracy, the Shilen tube I use sends it. Hard to beat this cartridge all around. Nobody has really made significant improvements in the wildcats.
The Norma brass is SOFT. IF you load it to standard book loads it will last fine. If you match factory specs, you will loose primer pockets much more quickly. And I assure you I have burned up many thousand rounds of Norma 338-378 Wby brass as we used to shoot the 338 Kahn exclusively for our long range shooting which is simply a 338-378 Wby with a 35 degree conventional shoulder instead of the double radiused shoulder.
We were shooting my Heavy V-Block rifles, one with 32" barrel length, the other with 34" barrel length. My rifle had the shortest barrel and it would get 3050 fps with the 300 gr SMK with a long OAL of 4.100" used as a single shot.
My brothers rifle with the longer barrel and same OAL would push 3100 fps easy enough but thats about it. At this level we were seeing 5-6 firings per case and generally the last couple were on very loose primers.
By comparision, my 338 Allen Xpress will hit 3000 fps with a 30" barrel length with the same bullet and I have NEVER loosened a primer pocket on the 338 Lapua parent case with any of my wildcat loads. That includes up to and well over 10 firings per case.
Last I checked the Wby boxed brass was running around $450 shipped to the customer per 100 brass. The Norma brass was running around $320 with shipping per 100. So you pay this much and get 5-6 firings at best per case.
You can order 100 338 Lapua brass for around $275 per 100 and get +10 firings per case with same level of performance and AT LEAST as good if not better case to case consistancy, there is no real decision here, plus you do not have the worthless belt to worry about.
When I was designing all of my Allen Xpress and Allen Magnum wildcats I started with the Wby case and necked it down to 7mm and modified it to 30, 338 and 375 cal and was not impressed with the results. Then I switched to the 338 Lapua and could not have been happier. Matched the performance of the much larger Wby case but did so with less powder and in a much shorter OAL which made them much more practical for a wider range of receivers to be use in.
In the end, the 338-378 wby case, no matter if its made by Norma or sold under the Wby name is not a strong case compared to what else is out there. And anyone that has used it alot and pushed it to top pressures knows this to be true.
No flame intended toward you, just the simple fact of life, its not very strong brass compared to others out there and vastly over priced for what you get in the end. A case that large in capacity should add 100 fps over what even the 338 Lapua Improved should be able to produce and it does not even come close to that. Barely matches the Lapua Improved and my AX.