Proper freebore for the 88gr Berger MEF or 87gr V-Max

[dkopriva]

I am chambering a 6BR to shoot the 88 grain Berger MEF or the Hornady 87 grain V-Max for long range varminting. I am looking for some advice on freebore lenght. This is my first 6BR and was initially going to go with .070 but thought I better do some checking before ordering a reamer.

Daryl K.

 

[flatlander]

Daryl - I just found your post - otherwise, I'd have posted this sooner. I've just started doing some shooting with both of Hornady's 87s - BTHP & V-Max - in a 28" Krieger 8-twist chambered for 6BR Ubl,Dasher with a .274" neck). The Ubl reamer drawing shows .1583" leade if I'm reading it correctly. All the 105/107s I've loaded for these chambers wind up with the boattail/bearing surface junction of the bullet about .050" above the shoulder/neck junction. This chamber allows both the 87s to be seated quite a bit farther out, yet still have good neck support, even if they're seated into the lands. While this gives max. case capacity, I think you could get good results with far less freebore - like the .070" you mentioned - as long as you don't intend to load 105/107s. I think I've still got the reamer print in an Excel format in my e-mail program if you'd like to have a look at it yourself.
Regards,
Dennis

 

[Forum Boss]

With a standard 6BR case, the .070 freebore will still keep the bottom of the bearing surface away from the neck-shoulder junction, with the Berger and Lapua 105s and the SMK 107s. The Amax 105s are a different story. We have Lapua 105s seated about .015" into the lands in a chamber with .073" freebore and the bottom of the bearing surface is .055" from the Neck-shoulder junction. But if you want to jump your bullets away from the lands, then you are getting closer to the NSJ than desireable. Therefore, we think a freebore in the .080-.090 range is more versatile, particularly if you want mostly to shoot the 105s/107s.

The Berger 95 VLD, with its very short bearing surface, will work with a freebore as short as .040.

 

[dkopriva]

Flatlander

Good to here from you last time we met I think was corn harvest.
Thanks for the info. I am running a 10 twist barrel so I won't be shooting any of the heavy long 105's and up. I settled with .060 leade on a Kiff reamer. Does anybody know if the 10 twist will work on that 95 grain berger the moderator mentioned. I have ordered some 80 grain Fowlers for shots out to 500 yds or so; maybe the 95 grain bergers would get me out to 800 or so. It's hard to hit those dogs out there but it is fun to try.

Daryl