Never loaded those calibers, but I have found RWS Hornet brass has smaller than normal flash holes..and it has proven to be the most accurate brass for this caliber so far.

I do have extended reloading experience with the 6ppc and a shortened 22 ppc so I can tell you that the flash holes are deliberate and a smaller decapping pin is required, smaller than the standard small rifle pin from say the 223 Rem dies.  Sinclair does sell everything you need for the ppc cases including the 220 Russian which is the parent case and one used by most shooters to form their brass.  I started reloading for rifles around 1960 and I learned more about precision reloading techniques shooting the 6ppc in competition then I learned in 40 years prior reloading.  When you have a rifle that will shoot consistently groups of 5 shots into one ragged hole flaws in your loading techniques as well as your shooting techniques show up very soon!  That is what amazes me about the cast benchrest shooting on this site is how accurate these single shots are with cast bullets!  Tom

I loved shooting B/R and learning to fine tune equipment and re-loading.  I just copied what the winners were doing. Other people had already done the hard work and costly constant barrel replacements extensive fine tuning,(including flash hole size) so once there , the next challenge was to become a good  wind reader . This is just as satisfying as you have total control as to your placement standing especially at longer range once you are competitive in loading