6br Freebore

[Dale264]

I know most reamers are 0.094-0.104" but I'm putting together a 6BR that will mostly shoots 70tnts, some 105s and less occasionally 55gr NBTs. Would a 0.060" freebore be acceptable for this? Preferred Barrel Blanks said they can get me any freebore I like so I'd prefer to get this thing set up right off the bat.

My last experience with a 0.098" FB had 105s at 2.375 and the 70s were a little longer than I hoped (2.240") but roughly 0.155" of bearing surface was in the case.

What are your thoughts on shorter freebore for shooting midweight bullets with the occasional 105?

Thanks!

 

[HTSmith]

What are your thoughts on shorter freebore for shooting midweight bullets with the occasional 105?

Good plan IMHO. I have had two .060's and was able to keep the heel of Berger 105 VLD's and 105 Hybrids just out of the neck/shoulder junction.

 

[rwj]

A short free bore combined with a 105 grain bullet will likely result in the bullet either being jammed into the lands or deeply seated with its pressure ring being located in/below the case neck/shoulder junction. It may work out fine. If it doesn’t, you won’t have much flexibility for tuning.

 

[Poor Shot 65]

I use different reamers to shoot different weight bullets. A zero freebore reamer to shoot 68gr and a .060" freebore reamer to shoot 80gr bullets.

 

[hammerjack]

A .060 reamer will work fine. Chamber length comes into play also on the reamer adding to freebore.

 

[Idaho-Lefty]

" I prefer to, get this thing right",...
For ME anymore, and to do the "Job",.. RIGHT,.. I pick a couple of, Bullets "close" to the SAME weight / Length and get THE right Twist for them, then use, the proper Freebore to, make an ACCURATE, Rifle !
Pick the "Job" you want the Rifle / Bullet, to "do" and,.. build for,.. IT !
Slow Twist, SHORT Freebore with the Lighter, FASTER Bullets to STABILZE in your barrel ! GOOD to, shoot Varmints and "Accurate", short range, Targets !
Build another Rifle for, the LONGER,.. Ranges ! Life's too short, to screw around with, a half asszzed, Rifle !
Sorry, don't mean to be Blunt but,. that's the ,.. TRUTH

 

[Idaho-Lefty]

I use different reamers to shoot different weight bullets. A zero freebore reamer to shoot 68gr and a .060" freebore reamer to shoot 80gr bullets.

YUP,.. Bingo !

 

[Idaho-Lefty]

A short free bore combined with a 105 grain bullet will likely result in the bullet either being jammed into the lands or deeply seated with its pressure ring being located in/below the case neck/shoulder junction. It may work out fine. If it doesn’t, you won’t have much flexibility for tuning.

YUP,. Bingo !

 

[jackieschmidt]

For most long range bullets built on 1.150 jackets, such as the Barts 103’s, the standard seems to be around a .105 freebore.
I tried something on a whim. I used my regular .269 neck .060 freebore reamer to try my own 103 grn bullets.
This is what the bullet looks like in the neck when being jumped around .015. At a flat 2900 FPS with 30.9 grns of N-150, it shoots pretty darned good.

 

[hammerjack]

Yep a 70 TNT and 55 NBT will fit in there too. That was the OP question.

 

[johara1]

For most long range bullets built on 1.150 jackets, such as the Barts 103’s, the standard seems to be around a .105 freebore.
I tried something on a whim. I used my regular .269 neck .060 freebore reamer to try my own 103 grn bullets.
This is what the bullet looks like in the neck when View attachment 1221787being jumped around .015. At a flat 2900 FPS with 30.9 grns of N-150, it shoots pretty darned good.

It would never work with a 103 Spencer... You can not seat the heel of a bullet deeper than the Sized part of the neck.... jim

 

[AckleymanII]

55-70g bullets love ZERO to .020 freebore.

start at the start

don't just "make do"

Plan for success

 

[johara1]

yes, it is not one size fits all. You a .100 freebore and lengthen it to .120 with a 105 class bullet, you have to relearn it because it changes everything. I saw a .012 change in free bore drive you crazy..... jim

 

[urbanrifleman]

For most long range bullets built on 1.150 jackets, such as the Barts 103’s, the standard seems to be around a .105 freebore.
I tried something on a whim. I used my regular .269 neck .060 freebore reamer to try my own 103 grn bullets.
This is what the bullet looks like in the neck when View attachment 1221787being jumped around .015. At a flat 2900 FPS with 30.9 grns of N-150, it shoots pretty darned good.

That is what I found with the 108 Bergers. They shoot fine jumped 30 thou in my 50 FB barrels. The prototype 6BRa barrel that I received for testing was 50 FB and it shoot the 108 Bergers the best.

 

[johara1]

Jumping them .030 and a .050 free bore, those have to really back in the case, what kind of velocity are you getting?..... jim

 

[VA_XTC_Shooter]

I am currently shooting 0.094" freebore with 70s to 105 berger VLDs and it shoots lights out. I am about to order a reamer for my new barrel and was planning to replicate the 0.094"

It seems the 0.104" is the off the shelf freebore for the 6BR, why? As many have shown above, its unnecessary for the 6BR 105s. Why extend freebore when not needed?

Some reference chasing or not chasing the lands. Would the difference in freebore then provide a different barrel life?

I am just trying to wrap my head around this discussion, not trying to talk down to others' opinions.

 

[Tokay444]

A lot of people want to find a farther, less sensitive to lead migration jump node, without pushing the base to bearing junction past the neck to shoulder junction, so we keep the cartridge length the same, and extend the freebore.

 

[VA_XTC_Shooter]

A lot of people want to find a farther, less sensitive to lead migration jump node, without pushing the base to bearing junction past the neck to shoulder junction, so we keep the cartridge length the same, and extend the freebore.

So not just having base to bearing above the neck to shoulder junction with a 0.094" isn't enough to find a node? Is the assumption there isn't enough room to seat bullet further to find the node without hitting lands?

 

[Tokay444]

Berger 105 Hybrids seems to have a node between .065-.095 jump which is almost completely insensitive to lead migration.

 

[Tokay444]

Probably not what a benchrest shooter wants, but for someone who needs to load 200-400 rounds and travel to a match and shoot them all in a weekend, it’s right up their alley.