New 6.5 CM Build Advise

Feb 13, 2017
Carrizo Springs, TX

About to get a 6.5 CM built. Need to decide on either .170” or .199” freebore reamer. I will be shooting the 140 eld m and 143 eld x.

Tons of folks run the sammi .199” and have excellent results with these two bullets and this is all I have ever had in the past with factory rifles. I know that masterpiece uses a .170” freebore reamer to chamber their barrels for the 140 eld m and am curious as to what the advantages and disadvantages to these two reamers would be. I will be using a stiller tac 30 with M5 DBM and AI mags.

Advice would be appreciated!
Feb 4, 2014
Most recent everyday sniper podcast touched on this subject. Personally I’d run the SAMI reamer, with the shorter free bore on the other reamer, as I understand it, will help with those bullets like the hybrid that still need to be somewhat close to the lands but not seated so long they don’t fit in a mag.
Likes: Dutch260
Feb 13, 2017
Carrizo Springs, TX
Here is something I learned yesterday. A buddy of mine had a creed built by gap last year that I did load development for. For brass, He broke in and sped up the new proof barrel with 200 rounds of factory 143 eld x. It shot 1/2 minute with factory ammo and 1/4 minute with the load I developed. I asked gap which reamer thaey used to chamber that barrel and it was a .152” freebore. MPA uses a .170” freebore for their rifles set up to shoot hornady as I noted in my first post. So, my question is: What is the advantage to running a sammi reamer with excessive freebore?
Sep 6, 2006
Southern California
There will be no performance advantage one way or the other. It’s just about magazine fit, and either will work there too. If you think you’ll be running longer nose VLD bullets at some point, go with the shorter freebore.
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