Is .355 interchangeable between 9mm and .380?

[fxvr5]

I doubt anyone that can actually read can mistake a reload for a store bought bullet. The 9mm wouldn't fit the .380 mag and vise versa.

380s fit in a 9mm magazine. They fit in mine.

 

[fxvr5]

I'm am loading and have shot 9Mm bullets ( currently 90 gr HP Sig great round) the bullets seats great @ .980 and I use 90 gr HP data.

Not many companies make strictly .356 bullets for the 380. Sierra and Hornady make .355 bullets for the 380 and 9mm. Speer's 380 bullets are marked .355. Only Remington and Winchester that I'm aware of make their 380 bullets at .356.

SAAMI specs for 380 bullets are 0.3565 - 0.006. So any bullet within .3505 and .3565 is within spec.

The 9mm and 380 Auto have the same barrel specs, which are 0.355" groove diameter. Interchanging bullets is no big deal.

 

[Maximum Headspace]

380s fit in a 9mm magazine. They fit in mine.

Not without a lot of slop they dont. Thete is quite a bit of space between the back of the magazine and the nose of the bullet. For me personally a pretty hard thing to over look. But plenty of YouTube videos of guys saying "tgey almost made a grave mistake " by loading a .380 in their 9mm.