Is my Shilen 6BR throat too short?

[johnsopa]

I have a new Shilen barrel in 6BR for my Savage. While I don't have a Stony Point OAL gauge, I usually approximate my OAL by seating a few bullets super long in lightly neck sized brass and then closing the bolt,no primers or powder of course).

I am using 105gr A-MAX bullets in this barrel,8 twist)
have found that my max OAL is about 2.29".

I am wondering if Shilen short-throated this barrel.

This seems awfully short for this type of bullet, doesn't it?

I am a relative newbie to the 6BR and am having some frustration getting it to shoot well, so I'm examining all options.

Thanks.

 

[expiper]

With the A-max seated that deep you are touching the do-nut area by about .010" ....sounds like the throat is around .030...good for the lighter bullets and maby Sierra 107's ....did they tell u what the freebore is??? is it stamped on the bbl...let us know how close it is to .030...Roger

 

[Forum Boss]

My Quickload program says, assuming a bullet length of 1.229",you should measure yours--Hornady has changed the design a couple of times), then you have 0.309" of bearing surface,shank), in the neck.

6BR necks are nominally 0.312" counting the neck-shoulder radius, so you're right at the neck shoulder junction. That could be causing some issues. You'll probably have better accuracy if you have the throat extended .040 or so.

But measure your bullets and necks first to make sure how far down you really are. For the 105s I like to have at least 0.200 in the neck. They'll shoot fine with as much as about .275" in the neck. Much deeper than that and you reduce case capacity and start to run into the doughnut area.

FYI, with one caliber,0.243") of shank in the neck, your OAL would be 2.356", assuming the bullet length of 1.229".

 

[johnsopa]

Here's an update. I talked with Shilen. Randy, the reamer expert, said that the reamer for the no-turn neck,0.272") has freebore set to the SAAMI spec, which he said is .060" of freebore.

He said that if I want, I can send the barrel back with a few dummy rounds with the bullets seated where I want them and he will use a throater to extend the throat.

Would 0.060" freebore put my 105 gr bullet that far down?

 

[Forum Boss]

Here's an update. I talked with Shilen. Randy, the reamer expert, said that the reamer for the no-turn neck,0.272") has freebore set to the SAAMI spec, which he said is .060" of freebore.

He said that if I want, I can send the barrel back with a few dummy rounds with the bullets seated where I want them and he will use a throater to extend the throat.

Would 0.060" freebore put my 105 gr bullet that far down?

Yep. Normal Freebore for 100-107gr bullets is about 0.100".

That's why I suggested throat being pushed about 0.040".

 

[expiper]

Hi John...my .080 FB chamber loads the A-max at 2.340...yours loads at 2.290....050 shorter ...that is why I was "guessin" it to be around a .030 FB...it prolly will work with Sierra and Berger VLD's....not the new Berger 105 BT,which is one of the best!!!!)....Try a Sierra 107 and the Berger VLD 105 ...they are great bullets,at least they have did well for me) ...and you wont have to re-throat!! Just my .02 $$ ...Roger

PS...send me a e-mail ...I will share what I think can help..

 

[johnsopa]

Roger, does this mean that the bearing surface of the Sierra 107 is shorter and/or lower down than that of the A-MAX 105?

If so, I will try that first.

 

[expiper]

Yes ..the shank on a Sierra and a Berger 105 VLD is aprox. .040" shorter in relation to where the nose of the bullet engages the rifeling.......in other words it will move the shank up the case neck aprox. .040 ...just what will work for you!!!!....Roger
It is amazing how much info that is NOT on the internet..haahah.