From a very good source reamer specs. Throat .357 bore .355, your not gonna shove a .358 bullet down it.
Winchesters press release says it uses .357 bullets and when you look at the Winchester loads for the cartridges there are several bullets that look much more like .357 bullets than they do .355 9mm bullets.
I looked SAAMI, hasn't put up the drawings yet.
As long as the chamber doesn't preclude, if the bore is set up for .357 it will likely shoot .358's. Its a pretty common practice to shoot .358 bullets through 357max contender barrels. I have shot a bunch of Hornday 358 SSP and 200ftx bullets out of my .357 barreled TC carbine with good accuracy and no signs of excessive pressures.
On an interesting note one of Winchesters loads is a 150g plastic tipped bullet, I love get those as a component.
edited to add, The ammo boxes say the bullets are .357
Last edited by noKnees; 01/23/19.
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