I hunted with factory loaded, pie-fold paper ammo from the 50's almost exclusively for 15-20 years. I may have had a misfire but I can't recall a single incident. I surely wouldn't have risked wasting a grouse flush if I had doubted the ammo.
By contrast, I found that roll-crimped stuff, no matter how pristine in appearance, was at high risk of duds. Perhaps some of the roll-crimped stuff that was still manufactured post-war would be more reliable...I suspect primer technology may have changed during the war effort. In any event, a simple rule of thumb to avoid roll crimps and embrace pie crimped shells has served me well.
