Why are my 338 bullets .337?

[Roblonsberry]

I’m stepping up to bushing dies for the first time. While doing some measuring on my components I was surprised to find that certain bullets weren’t .338 in diameter. Hornady and Berger were both .337 wide while all my Lapua were .338.
What gives?
I figure since my Lapua brass seems like it’s .0145 to .0150 a .365 bushing would do? I am using Mititoyo calipers. Don’t have a ball mic yet.

 

[ShootnFool8]

Believe that is the most common bushing being used. But, again one will tell you to measure your neck with a round in it. Minus 2 thousandths. That gives you your bushing size. I use a 365 bushing.

 

[Mike Casselton]

Make sure to wipe the jaws on your caliper and zero them.
You can easily be off a couple thousands due to dust and dirt particles.

Wipe, then zero.

I never use mine without wiping them.

Let us know if that changes your measurements.

Lastly, where on the bullet are you measuring?

 

[Roblonsberry]

You were right. I cleaned them off now they’re all .3380 -.3385
Thank you