How do you know what length to trim to?

[headhunter]

I just got a 6x47 Lapua and am wondering what length to trim the brass?
New 6.5x47 Lapua brass is 2.847 after necked down. The fireformed brass that came with the rifle will go from 2.850 to 2.856.
Can anyone steer me in the right direction or is there a way to measure to tell the correct length?

Thanks in advance for the help.

 

[fdshuster]

Sinclair chamber length gauges, 2010-B catalog, page 37, item# G-243 or #G-243T at $6.95.

 

[artbosco]

I just got a 6x47 Lapua and am wondering what length to trim the brass?
New 6.5x47 Lapua brass is 2.847 after necked down. The fireformed brass that came with the rifle will go from 2.850 to 2.856.
Can anyone steer me in the right direction or is there a way to measure to tell the correct length?

Once you get the Sinclair Chamber Length Gauge and determine your true chamber length, use .010" for each increment.

For example, if the chamber length is 2.860" from the base to the end of the neck in the chamber, then the maximum case length would be 2.850" [a .010" safety zone] with a trim to length of 2.840" [another .010"]. Don't let the cases get over 2.850" and you'll be in good shape. Please note: This is only an example.

 

[headhunter]

Thanks for the help. I will order the gauge tonight.