For God's sake people, read the O.P. slowly before you post. Yes, he is talking about cast bullets, yes he is pushing the bullets, not the cartridges through the chambers.
...The cylinder might be tight to prevent "bullet creep" from a heavy recoil dislodging bullets...
Yeah...if S&W just decided that they would ignore SAMMI specs for a .357 chamber or just want to have the guy blow up his gun...
Original Poster, you may want to visit here: http://castboolits.gunloads.com/
, you are more likely to get better advice that what you have been getting here.