xshare: Lapua is known for its quality ammunition and their loadings should be commensurate with other current european loadings such as S&B and possibly, Norma - these later two are known for loading ammunition to its original specifications. If the recoil on your ammo is noticeably less than with other ammo it may have been loaded for the American market, which is both 'old gun' and 'liability' crazy regarding hot (hotter than US ammo) in older rifles.
You mentioned chambering difficulties or trouble loading from the magazine. You also said 'round nose-flat point ammo' - just how large is the flat point compared to normal ball ammo??? If you stand a loaded mil-spec ball next to a loaded Lapua rnfp, is the oal the same? If it is the bullet may be loaded too far out to properly feed in your 48A. Remember that the 48/48A is an intermediate length action and the oal of a 57mm case may be the maximum length cartridge that action can handle (sort of like the 30-06 in mil-surp Mauser actions where you could only load 3 into the mag due to the oal of the 06 vs the oal of the 8mm.
My 48A just loves the S&B ammo, both ball and spce (soft point cutted edge - looks like a bit of a swc in jacketed soft point configuration) and just about any other 8mm ball. The Lapua may be a bit long for your 48A.
This is something I will have to try and experiment with. I started reloading the 8mm for my Swedish 98. I find that if I load 200 gn Nosler soft points so that they just touch the rifling, the oal is the same or longer than that of a loaded Winchester 180 gn soft point. I haven't tried any of these loads in my 48A but I should to see if they are still within specs to strip them from the magazine.
It may be the flat nose configuration that is hanging you up or it may be the cartridge oal. I would try some S&B - it is loaded to original factory specs and it is quality ammo. HTH. Mikey.