Nomercy448

Factory ammo for the Legend uses .355” bullets because they have the luxury of doing so - and they’re making the brass. The Winchester spec for the chamber does not allow standard neck thicknesses when using a minimum chamber dimension coupled with their max spec’d bullet dimension. So instead of making brass to fit the appropriate bullet dia, they just made the bullets smaller.

However, the bore - that which dictates the actual peak pressure - is spec’d the same as every .357 magnum or maximum ever built. Same groove and bore dimensions. So you’re not really “increasing” pressure by using a .357” bullet, but rather are “decreasing” what it really should be running by using an undersized bullet when running .355-.356”.

Ultimately, we smash bullets a lot harder every day in other cartridges than we’re talking about in the Legend. Do your load work up, watch for signs, same as everything else.

Also of considerable note - the 180grn Speer HotCor has a considerably shorter bearing surface than any of the .357” revolver bullets which could be used in the Legend. I put more powder under a 180 Hotcor with lower pressure, running 150-200fps FASTER, than I can get under a 158 XTP-FP. I can dump a grain and a half more H110 in a B&D case under the 180 and not even see craters than the lighter load under the 158, which produces craters with primer flow (total top hats!) and sticky extraction. So it ain’t all just about diameter and mass - the shank design and profile play a huge part in establishment of the pressure curve.