If you are using the RCBS tool, don't use the mandrel they give you to hold the case on. Use a Seating die to hold the case.
Not every Berdan primed case is easily reloadable, for several reasons. The first is you have to have the right Berdan primers. Berdan primers are made in a bewildering aray of diameters, heights, strengths and hardnesses. Right now there are two different .217" Berdan primers made by Murom in Russia and easily available from TulAmmo, one intended for 7.62x39 class cartridges, which is shorter, harder, and has less explosive strength:
http://www.dagammo.com/shop/index.php?main_page=product_info&cPath=7&products_id=46
The other is taller, seems to be softer, but has much more explosive strength:
http://www.dagammo.com/shop/index.php?main_page=product_info&cPath=7&products_id=47
The second primer is the one PMC imported some dozen years ago under their label, and has worked great for me in .217" primer pockets.
There are a lot of different sizes of primer pockets. Most .303 is .250", although all the FN .303 I've seen is .217", and some South African from the early 1980's was .217". Of 7.62x54R, all of it has .254" pockets, except for early Bulgarian and all Albanian, which are .217". The Czech 7.62x45 I have has pockets that are about .197".
The other big problem with some Berdan brass is that sometimes they have heavily staked primer pockets, and they may have a sealant that has much in common with epoxy resin. The worst I've come across is the South African .303 from the 1980's.
Berdan primers are typically more gentle than Boxer, but I once got sky high pressures with 8x57, using the same load that was moderate with Boxer brass.