Trim length for 300 BO

TexasHaag

Sergeant of the Hide

Full Member

Minuteman

Jul 3, 2022

101

39

Killeen Texas

Mar 24, 2023

#1

• Mar 24, 2023

• #1

Greetings
Here is my question about trimming brass, I'll use 300 BO for example, but it applies to most cases.
SAAMI says 1.368 - .020 ok that gives a trim length of 1.348. I'm seeing lots or references to 1.363 that is only - .005.
what's the deal... can anyone explain?

texashaag

 

spife7980

Luchador

Full Member

Minuteman

Feb 10, 2017

13,849

17,051

Central TX

Mar 24, 2023

#2

• Mar 24, 2023

• #2

1.368 minus .020 is 1.348. Anything in between those two max and min numbers would be in spec range.

Most recommendations are to go to the middle which would be 1.358.

 

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B y r o n

Private

Full Member

Minuteman

Nov 8, 2004

1,107

760

Western Kentucky

Mar 24, 2023

#3

• Mar 24, 2023

• #3

If you are seeing case length figures from SAAMI that list 1.368 -.020 it means that the maximum case length is 1.368 but if .020 less that is acceptable. SAAMI does not list trim lengths which is really an arbitrary number. For rifle cases .010 below maximum length is normally listed.

 

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Hoser

Ninja

Full Member

Minuteman

Apr 12, 2005

1,967

1,403

East Africa

Mar 24, 2023

#4

• Mar 24, 2023

• #4

I have been trimming my 300 Whisper/Blackout to 1.355 for about 15 years now.

This means it will fit in all the different flavors of the 300 chamber.

 

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