Lebel brass can be made from .348 Winchester brass using a special forming die. Some folks use their full length sizing die to form .348 brass but it also tends to crack dies at some point. Grafs and Sons, Buffalo Arms both sell Lebel brass for around #35.00 a hundred. I have used it quite a bit and it has held up well, Joe
.348 works well for forming 8x50R Lebel, but it is becoming difficult to find and I wonder if it is not being dicontinued. At least Midway was showing it as "seasonal" at one time. Haven't looked recently.
Graf and Sons carries new made boxer primed Lebel brass. I have used it with great success and have had little trouble ( a couple of split necks after firing it in my French 1917 RSC). I too have used .348 Winchester in the past, but as long as new stuff is available, I won't use .348 again.