BillK,
What cases are you using? You said you are not using Bertram's. If you are using original cases, they would take the 5.5 MM (.217") Berdan primer, which are in very short supply (unless you have some "squirreled away"). If the cases are formed from American donor cases or "modern" 9.3x72R cases pocketed for Boxer primers, you can use pretty much any large rifle primer you like (I'm guessing you will reduce the charge and work back up to it, as per normal). Some older combination guns (especially drillings) give problems firing modern boxer primers because the firing pins strike the harder primer cup at an angle. My friend and mentor Gene Enterkin kept a stash of what he called "round head primers"(actually older round headed large pistol primers) use loading for rifles giving this problem. The theory was the firing pin would strike the primer closer to "straight on" to the rounded surface, in addition to the cup being "softer". You won't know whether you will need to resort to these primers or even modify the rifle, unless you have misfires or hangfires with it.
Mike
