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P Flados · December 18, 2019, 11:36 PM

Ok, here is a summary of the 350L diameter stuff based on what I had previously posted elsewhere.

The 350L SAAMI spec allows 0.354 to 0.357 bullets and the bore is to be between 0.355 and 0.357.

The guns and factory ammo are being made very close to 0.355.

The choice to make the guns and ammo at the bottom of the allowed tolerance ranges is not typical and is a big part of the confusion.

The chamber neck in combination with the thickness of Winchester brass made it such that very few people could get reloads to chamber with 0.357 bullets. The first run of Starline brass was thinner and some found that 0.357 worked with Starline brass.

Others have been having good luck sizing down 0.357 and 0.358 jacketed bullets. Most are sizing to 0.356 (0.355 is not a standard Lee push through size).

The made for 350L bullets are generally very close to 0.355.

Note that the SAAMI spec for the 357 magnum allows bullet diameters from 0.355 to 0.358. Therefore, the state (Iowa) that specified at least 0.357 minimum diameter (instead of 35 cal), was not paying attention to the fine print when they wrote their rules. They wanted to allow the 357 magnum, but did not realize that an ammo maker can ship "in spec" 357 magnum ammo as small as 0.355. I think Winchester used this argument to get them to accept the 350L. Iowa has publicly stated that they are going to ignore tolerances and actual measured diameters and allow using the 350L because of what is on the side of the ammo box (0.357).

December 18, 2019, 11:36 PM	#100
P Flados Senior Member Join Date: January 8, 2017 Location: Wilmington NC Posts: 243	Ok, here is a summary of the 350L diameter stuff based on what I had previously posted elsewhere. The 350L SAAMI spec allows 0.354 to 0.357 bullets and the bore is to be between 0.355 and 0.357. The guns and factory ammo are being made very close to 0.355. The choice to make the guns and ammo at the bottom of the allowed tolerance ranges is not typical and is a big part of the confusion. The chamber neck in combination with the thickness of Winchester brass made it such that very few people could get reloads to chamber with 0.357 bullets. The first run of Starline brass was thinner and some found that 0.357 worked with Starline brass. Others have been having good luck sizing down 0.357 and 0.358 jacketed bullets. Most are sizing to 0.356 (0.355 is not a standard Lee push through size). The made for 350L bullets are generally very close to 0.355. Note that the SAAMI spec for the 357 magnum allows bullet diameters from 0.355 to 0.358. Therefore, the state (Iowa) that specified at least 0.357 minimum diameter (instead of 35 cal), was not paying attention to the fine print when they wrote their rules. They wanted to allow the 357 magnum, but did not realize that an ammo maker can ship "in spec" 357 magnum ammo as small as 0.355. I think Winchester used this argument to get them to accept the 350L. Iowa has publicly stated that they are going to ignore tolerances and actual measured diameters and allow using the 350L because of what is on the side of the ammo box (0.357). Last edited by P Flados; December 21, 2019 at 12:52 AM.