Long throat 6mm br project

[JOHN708]

I’m thinking of doing n new 6mm br build utilizing a .150 to .200 free-bore vs a standard .105. In theory this should reduce pressure allowing .5-1 gr more powder which should get me to around 2880 to 2900+ fps with the 105-108 gr bullets while still giving me more useable neck than a 6BRX. I’m sure someone has tried this in the past on more than one occasion and I’m interested if it’s worth it. Comments?

 

[swd]

The BRX and Dasher have plenty of neck and if you really want a longer neck do a Norma Dasher, which is .050” longer than a Lapua case.

 

[urbanrifleman]

I’m thinking of doing n new 6mm br build utilizing a .150 to .200 free-bore vs a standard .105. In theory this should reduce pressure allowing .5-1 gr more powder which should get me to around 2880 to 2900+ fps with the 105-108 gr bullets while still giving me more useable neck than a 6BRX. I’m sure someone has tried this in the past on more than one occasion and I’m interested if it’s worth it. Comments?

My new 6bra reamer is 160 fb, same as the 6xc Tubb. Which I have determined is ideal for just about everything above an 80 grain Berger.

 

[JOHN708]

Thanks for all your replies.

John

 

[LRPV]

I had a BR barrel once that was .155 I believe. I could run 32 grains of Varget with 103's in that BR barrel and not see pressure signs. I could never get it to shoot very good and I don't remember what the velocity was but should have been 2900+ with that much powder.

 

[Rat Rifle]

I had a BR barrel once that was .155 I believe. I could run 32 grains of Varget with 103's in that BR barrel and not see pressure signs. I could never get it to shoot very good and I don't remember what the velocity was but should have been 2900+ with that much powder.

How many rounds can You get out of a barrel like that before You don’t have enough bullet in the case neck ??

 

[LRPV]

How many rounds can You get out of a barrel like that before You don’t have enough bullet in the case neck ??

I don’t know. I guess you could just keep increasing the jump.

 

[NorCalMikie]

Long throat? Can't load close to the lands and every round fired makes the throat longer.
You find a load the "works" close to the lands and before too long, the throat gets too long and your favorite load goes away.
Get the freebore you want starting out but expect to be replacing barrels because the throat is too long.
ZERO freebore and start with the lightest bullets you can get your hands on and go heavier as the throat wears, and it will. Probably sooner than you would like.
Been there, done that and got a short freebore barrel/chamber and sold the long freebore to someone that wanted to shoot heavies.

 

[urbanrifleman]

A 6br has a 300 thou neck. An increase of 50 to 60 thou is not very much.

 

[JOHN708]

Thanks for everyone’s responses. A long throat 6 Br will still have more neck than a BRX. The only reason one would do a long throat is to shoot 105-109 gr bullets which is what I usually use at 600 yds. The goal would be to split the velocity difference between 2800 and 3000 fps with a given load. At 600 yds this would equate to a 1/10 in difference per MPH in x wind deflection.

John

 

[swd]

Thanks for everyone’s responses. A long throat 6 Br will still have more neck than a BRX. The only reason one would do a long throat is to shoot 105-109 gr bullets which is what I usually use at 600 yds. The goal would be to split the velocity difference between 2800 and 3000 fps with a given load. At 600 yds this would equate to a 1/10 in difference per MPH in x wind deflection.

John

A 109 doesn’t even use all the neck in my .140FB BRX. You just don’t need more neck..

 

[urbanrifleman]

People aren't really doing their homework on freebore. And the donut does not form at the neck junction it is actually above it.