I just run a stock mag, but mostly single feed as it's my 11 yo's squirrel rifle.
50 gr vmax don't fit in the mag if loaded to kiss lands.
Had to find my old notes, but I've got the magbox at 2.307 and 50 Vmax kissing at 2.273, 75 Amax kissing at 2.438. 50's feed fine from the box, 75's not a chance.
