6 mm BR need help

E

Evelio

Member
I just finished chambering a heavy varmint 8 twist barrel in 6 BR Norma. My reamer is a .271 neck with .045 free bore. Using Lapua brass, BR4 primers, and 30 grains of Varget with Sierra 107, and Hornady 105 bullets, I am getting 100 yds. groups from .200 to .300. At 200 yds, out of 10 shots 5 will go in a 1/2" group and the other 5 will open up the group to 1" to 1 1/2" really not acceptable.
The bullets are seated with about .010" jam, overall lenght 2.330" which puts almost half the bullet in the case. I am thinking that it will perform better with the bullet sticking out a lot more. I would like to run a throating reamer back in and make the free bore longer, but would like some experts opinions before I do anything.
Thank you.
Evelio.
 
How much have you played with your load? With your shorter freebore, you have what amounts to a slightly smaller case. How did you arrive at your load, including powder charge and seating depth? What are the neck diameters of your largest loaded rounds?
 
Evelio...your gettin ther....practice=practice is all you need....rember your FB is a little on the short side for the "big" (105 class) bullets....and they are purdy far down in the case neck all ready when jamed....if the COAL gets (with 107 SMK) near 2.300 you are gona touch the donut with the shank/base of the bullet....stay at least .010" above that....you can try jumping them seated at 2.310...and see how it goes ....the 105 Hornadays seat wayyy deeper than the Sierra's and are not very well suited with your short FB....I would stick with the SMK's and maby try Rx-15 !!??.....If you do lengthen the FB...go VERY carefull and SLOW...a throater will cut just the land out of the bore and they are thin as broomstraws...if you dont watch out you will be half way down the bbl....take a measurement when you start and carefully go in about .050...then maby a lil more to .080 which will give you around a .120 FB...which is good for the bigger bulets....let us know how it goes...Roger
 
I think that Dave Kiff may make a setup with a spiral throating reamer, something that goes in the chamber body area, and two stop collars. You spin the throater backwards to find the existing throat, set the front collar and then insert feeler gauges between it and the second equal to the desired increase in length, set the second collar, and then loosen the first, slide it back to the second and secure it.
 
Roger & Boyd
Thanks for the reply, PTG is out of 6mm throaters, and they said at least 8 weeks to get one. Brownell's had one in stock, and be here Monday, I already pulled the barrel off, and it is in the machine all dialed in, I will ream another .070" to .075" which will give me between .115 to .120 free bore. I should be able to shoot it again next Tuesday.
Evelio.
 
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