Neck clearance

[dmg264]

I have 6x47 in the works started doing some brass prep. The question is what kind of neck clearance do most of you run for this cartridge. This gun is going to be used for some local matches and possibly for F class. I was thinking about .002" clearance. Is this enough?

 

[Steve Blair]

I run .003 in my 6mm Remingtons and 6BRs. .002 will work but you should monitor neck thickness.

 

[camac]

For this question you will get a lot of different answers and all comes down to personal preference.
A good bit of advice I received once was "unless you know exactly what you want - pick the middle ground of what everyone is advising you to do"
As Steve said 0.002 is OK but does not give you much room to move. I would consider this on the low end. You will have to minimum turn or at least check all cases to remove the slightest of "bumps". Some fantastic shooting has been done with this level of neck clearance but with particular attention to detail. Some would say you might see a negative effect on accuracy at this level (probably due to a "lumpy neck" somewhere). 0.003-0.005 is "common ground" on 6.5mm cartridges but there are plenty of 0.002's around.

 

[stenger]

i run .002 in my 6.5.284 and plan on running .002 in my new 6mm 284. my thoughts is that if its to tight then just take more off until it shoots.

 

[dmg264]

I'm using .002" on my 6BR with no problems. If folks are using .002" on the 6.5-284's then I should be alright. Thanks for the replies.

David

 

[TonyR]

If you are working with tight clearence, it might be worth checking the diameters of the bullets you are using, particularly if you use bullets from different manufacturers. I have found close to .0007 inches differences between the diameters of the 7mm 162 A-Max, Berger 180VLD and 177 Cauterucios. I am set up for a 0.310 loaded neck in an 0.313 chamber neck so this didn't cause me any problems but I'm not sure what might have happened if I started out with necks turned for 0.002 instead of 0.003 inches clearance.

 

[Steve Blair]

My .284 reamer is similar, Tony. I had PT&G grind a .313 neck by .220 throat, 1°-30' leade. It is set for .310 loaded necks.

What initial throat dimension do you use?

 

[TonyR]

Hi Steve.
My reamer is made from the 284 Shehane print on the 7mm Cartridge Guide.
http://www.6mmbr.com/7mm284.html#284win
I found that the 180 Berger VLDs were too far into the neck with a new barrel, even jammed 0.015 inches, so I have an extra 0.020 inches put in by my gunsmith. Solves all of my problems. The 0.310 loaded neck with 0.003 clearance is extremely accurate but, as I said above, I had loaded a bunch of Cauterucios for a match that ended up with about 0.0015 in a couple of cases and it was too late to do anything about it so I shot them and they did great. I measure the diameters on bullets now because that lot was all over the place. Worked fine at 600 yards but I wouldn't have wanted to shoot them at 1000. Same lot of bullets sorted by diameter, bearing surface, and weight have been some of the most accurate I have ever put through the guns. I am just a lot more careful now.

 

[Steve Blair]

Tony,
My reamer is intended for a Brux 29" in a Borden TG action, Eliseo tube gun chassis and Highpower. I was hoping to get a little more barrel life by allowing for throat erosion. The barreled action arrived today from Borden and I will certainly consider your experience. Thanks.

 

[TonyR]

Steve.
You should be fine for high power. I shoot F-Class and pay a lot more attention to vertical than most of the LR prone guys I know. I have a Brux barrel and it shoots very well. It is a 31 inch .276/.284 1:8.5 twist and I have found it necessary to use Cauterucios/Sierras or thick jacket Bergers if I shoot it at the 2900+ node. Good luck with your project.