Throat measurements

[RonS]

What is the normal or SAMMI spec throat measurement for a 6-6.5x47 Lapua. Mine measures approximately 0.200". When seating a Berger 105gr. VLD touching the lands my longest COAL is about 2.679", the Berger manual COAL should be 2.800". The base of my 105, 107 and 108gr bullets are below the body/shoulder junction when seating them with 0.010" of jump, which produce excessive pressure. When I seat these bluest to 2.800" , the boat tail is in the should/neck junction and definitely will not chamber. So I am going to load Nosler 80gr SP and Hornady 87gr V-max bullets seated with about 0.050" jump using RL17 and IMR4350 and CCI 450's in hopes I have no more pressure issues.

 

[fguffey]

I would determine the two diameters of the barrel at the beginning of the rifling. I would then determine the distance from the bolt face to the beginning of the rifling. For me it is a matter of drilling the flash hole/primer pocket of a fired case then neck size.

After neck sizing for all the bullet hold I can get I remove the bolt, chamber the test case and then use a cleaning rod through the primer pocket to push the bullet out until it contacts the rifling.

I know, different bullets, different contacts. Getting past that, the beginning of the rifling does not change and the diameter stays the same. Yes, I understand, after firing a few thousand rounds there are changes.

F. Guffey

 

['Freak]

Smells like the reamer used to cut the not a standardized chambering of your barrel was of a design intended more so for those wanting to shoot much shorter, lighter projectiles.

 

[RonS]

I would determine the two diameters of the barrel at the beginning of the rifling. I would then determine the distance from the bolt face to the beginning of the rifling. For me it is a matter of drilling the flash hole/primer pocket of a fired case then neck size.

After neck sizing for all the bullet hold I can get I remove the bolt, chamber the test case and then use a cleaning rod through the primer pocket to push the bullet out until it contacts the rifling.

I know, different bullets, different contacts. Getting past that, the beginning of the rifling does not change and the diameter stays the same. Yes, I understand, after firing a few thousand rounds there are changes.

F. Guffey

I used a Hornady modified case to determine my findings.....

Smells like the reamer used to cut the not a standardized chambering of your barrel was of a design intended more so for those wanting to shoot much shorter, lighter projectiles.

I'm beginning to think this barrel was designed as a varmint rig but the barrel is one inch at the muzzle and 30" long. By the way did I mention that I bought this barrel used?

 

['Freak]

If the twist rate is capable of stabilizing the longer heavier stuff, have your ‘smith lengthen the distance to the leade so that with the longest of any bullets you intend to be shooting seated out to contact the lands, doing so would also leave the full length of the bullet’s bearing surface parked forward of the neck/shoulder junction.

 

[Torge]

RonS,
I have shot this for several years with tactical and BR rifles. Since it's a wildcat you won't be able to find any official specs. I think the 2.8" spec in the Berger manual is a maximum length. I have over 900 rounds through the barrel on my tactical gun and have chase the lands with a uni-throater and the COAL (base case to tip) is now 2.732" with VLD's jumped .010". At the 2013 NW MT 1000 yard BR Championships at Deep Creek that gun won the light gun with a COAL of 2.681" jumped .012".
The free bore is .104". Don't worry about the base of the bullet. The biggest problem with this is that the pressure band at the base of the shank needs to be seated in the sized portion of the neck. If you seat that pressure band deeper you will feel the resistance drop when seating as tho the bullet is falling into the case. The pressure band expands the neck enough to cause reduced tension or grip on the bullet if seated to deep. I have had a lot of target Hybrids and some VLD's that didn't have a pressure band and have never had a Lapua with one in 6mm. The VLD hunting bullets that most of us use have pressure bands that are .0003"to .0005" larger than the shank diameter.
If your bullets have a pressure band size you necks as far down as possible. Maybe get a die that sizes to the neck shoulder junction. This neck is long enough but if you use a Wilson neck die you won't size much more than half the neck and it will cost you accuracy. My Whidden bushing die can size almost all the neck and works well.
You could consider using a uni-throater.
David

 

[RonS]

Hey guys, thanks for the advice but I think if this barrel will stabilize bullets between 80 and 90 grains I'll leave it alone for now and maybe focus on a 6.5x47 Lapua for beyond 600 yards. In the 6x47 L pressure was off the chain using 105gr and heavier bullets with recoil greater then my 308 running 175's. But I am going to let my gunsmith look at it and make a recommendation