Stop with worrying about getting it to chamber!It almost chambers in a S&W m19.
What little difference in size shouldn't make much of a pressure difference, but I don't know either.
Bullet diameter is the least of the worries. Sounds like he is running live ammo through the sizing die. If that’s the case, the bullets were swaged down at the same time.Stop with worrying about getting it to chamber!
As Txtaxman says and Gmac emphasizes, this is a very bad idea.
The SW 38 bullet is .361; the 38 special is .357 => the SW 38 is 4 thousandths larger => you're going to get some really high pressure when the gases try to push that bullet through a 38 Special/357 barrel.
I ran one rd through the die. It left a bulge the thickness of the shell holder. It will chamber with a little push. The factory loads actually go in better. Might have to pick and choose chambers.