6BR Freebore?

[James EPS]

What freebore are most guys using or wished they had in their 6BR or improved versions shooting,

105 Berger VLD
105 Berger Hybrid
105 Amax
107 Sierra
etc....

I know most of the 6 cal bullets are 1.200 -1.250 with the Hybrid being prob the longest of all.
Also what neck would be a no turn with the new blue box lapua brass.

Thanks for the info
James
E.P.S Bullets

 

[bugman]

My Kiff reamer is spec'ed at .104 FB, and I have never had a problem with this FB for 103 to 108 grain bullets in a standard 6 BR. I have no experience with the berger 105 hybrid. It is the bearing surface that matters, and not the gross length of the bullet.

Also, after the first couple hundered rounds, the just touch is usually out 3 or 4 more thou. than the "new" chamber calculaltion.

My experience agrees with the previous poster that the blue box neck thickness says that a "no-turn" 6BR would be .2700 to .2705.

Jack

 

[jdfletch]

James,

6BR and the "improved" cartridges will have different freebore values because of the neck length variations. As for the 6BR and the 105 class bullets, I have a Kiff reamer with 0.104" freebore which fits all the bullets mentioned pretty well. However, if I were to do it again (and I will!) I would get a 0.094" freebore as it would set the VLD and Hybrid about perfect in the case neck and it will allow you to chase the lands for much of the barrel life. The AMAX and Sierra will be back a little at first, but after a few hundred rounds through the barrel they'll be about perfect as well.

Remember that the freebore value is related to the bullet length to ogive, not bullet OAL...

Doug

 

[James EPS]

Guys, thanks for the info on this subject. I was thinking pretty much along the lines as you guys. I have been shooting mostly my 30BR in score matches this year because I started making my own 118gr bullets on Detsch carbide dies with better than expected results. So now my focus is on 6mm bullets. Dave and I are in the final stages of development of a 105 class high BC boat tail bullet for the 6BR type cartridges. And of course I need to produce a bullet that I can sell to the masses. So I am researching the freebore information so I can finalize my bullet dimension and get the dies finished.

Thanks again ill keep you all posted,
James E.P.S Bullets

 

[johara1]

If you use the 105H or the BIB 108 you will need a .120 free bore in the BR. This will keep the heel of the boat tail above the shoulder neck area. If not you will get erratic neck tension. Chasing the lands is kind of beating a dead horse by the time you think you need to move the bullet into the lands the accuracy has dropped off and is no longer useful in the long range game....... jim

 

[James EPS]

.120 for the br what about the BRX maybe .110?

 

[expiper]

ESP ...(James/tinman)...the BRX and DRX and Dasher and most all of the "Improved" BR's have shorter neck lenght....so with a shorter neck you have less useable neck to work with(listen to Doug/jdfletch in an earlier post),,,thus the bullet (bearing surface)must be seated less (shallower) in the neck to avoid the neck/shoulder junction (donut area)....and that means the freebore length must be more to allow the bullet to be seated further out,,,,Roger
PS,,Everyone,,,,correct me if im not sayin it rite,,thank you

 

[johara1]

Don't know about the BRX. but the Dasher I run this year a.155 FB. for the 115 DTAC. and the 105H. I have a new reamer with a .135 FB. to try this year...... jim

 

[Rtheurer]

ESP

I concur with Doug as we us the same reamer. Its a .104 FB on the regular ole BR chamber. With the 108, 105 AMAX, and 107 SMK its about prefect. But with 105gr VLD's and the hybrids its a little long. I have been shooting the VLD's pretty much Exclusively so now I wish I would have gone to a .095 ish freebore.
Maybe Ill send it back PTG and have it set back and if I need to throat out the chamber I can always do that latter with a throating tool.

Its awful hard to put metal back after you cut it off it turns out...

 

[dreever]

Myself I go against the mainstream and have used a .060 freebore reamer for 105 VLD's in a 6BR Norma for years with no problems. I still get the velocity needed and can chase the lands for a long time.

Danny

 

[WayneShaw]

Danny has it right. For a regular BR, you can get away with as little as .040" and still not have the bullet in past the neck/shoulder. This give you the ability to use many bullets, plus gives good load density. And plenty of room to chase the lands.

BRX and Dasher has less neck, so you need to be more specific with bullet/throat match.

 

[James EPS]

Lots of good info. I have a question, do any of the improved versions retain the longer neck the standard 6br lapua has? And is it possible to just run a regular 6br reamer .100 deeper?


Thanks
James

 

[Phil]

The BRDX comes close.......

If i remember correctly it moves the neck shoulder junction forward .039".

 

[jkohler]

The neck on the BRDX is .039 tho shorter than the 6BR. I'm thinking the shoulder is .070 longer than a 6BR

 

[James EPS]

Appreciate all the info thanks