I have used cast in mine and have had good results, though some people report poor accuracy using cast in the 348.Throat fit is important with cast and I'd suggest using a Lee FCD to assist in fitting the bullet to the throat.
The 348 has a fairly long neck, which means with designs weighing less than about 240 gr or so you should be able to contain the lube grooves and the GC in the neck. Some people advise not to load cast pills where the rear of the bullet projects below the neck line. The reasoning is that the rear of the pills may be bumped up on ignition, then it's squeezed through the neck affecting accuracy. Before I read this I had already tried quite a few high speed loads using 270 gr cast GC in my Browning. These bullets do protrude into the powder space but accuracy was fine.
The prospect of a cast GC bullet losing its GC is a possibility, but it really depends on the calibre and type of GC. Some cast bullets have what I would consider to be undersized GC shanks. The 458 designs are one of the worst offenders. I've never had an issue with 348 cast pills using crimp on GC's made by Hornady. The other point worth making is that there are a few GC now made from aluminum and if not made to the correct dimensions, these may slip off easier than old school crimp on copper GC's.
