Ghostrider,
A chamber cast shows the dimensions and shape of the chamber, not the cartridge. The cartridge dimensions must be smaller than the chamber, or it will not enter the chamber. The difference between dimensions is usually between .005" and .010". but in very old cartridges they may exceed .015". The shoulder on the cartridge was formed by a die and when (if) fired, it will become "fireformed" and conform more closely the chamber. The photo clearly shows there was a problem, with seating the bullet, which, in my opinion, is the likely cause of problems in chambering the cartridge. You can check/confirm this by smoking the bullet and neck/shoulder area with a lighter or candle or by coloring it with a "magic marker". Then when you attempt chamber it, areas of interference will be clearly shown by the smoke being rubbed off. This shows why I recommend loading your own ammo as you can control the equipment and procedures/workmanship and can correct any problems. If you can chamber the cartridges with moderate pressure of your thumb and fire it, the case will be fireformed to the chamber and reloaded with no problems. If it will not chamber at all, you should pull the bullet, resize the case after emptying the powder/removing the de-capping assy./lubing it, then properly reseating the bullet after replacing the powder.
Mike
