Questions on 6BR blue box

[JHardy]

I am out of my cardboard box 6BR brass. I understand that the blue box has a different neck diam. and length as well. I want to properly spec a new reamer from JGS. In that regard, what is the neck thickness of the blue box and what is the OAL of the brass.

Thanks in advance,
Jim Hardy

 

[mr45man]

I would suggest getting a barrel's life worth of brass first,
then spec your reamer .
John H.

 

[Terry]

Once you have fired the brass, turned necks, and trimmed to length, what is the difference?

 

[JHardy]

I appreciate your response Terry. But, it can make a lot of difference. Forgetting the thickness of the brass for a moment in light of the fact that you are neck turning, there is a big issue remaining. If blue box is shorter than cardboard box 6BR Lapua brass, and you also trim your cases, and you have cut your chamber with a standard 6BR Norma reamer ground for the cardboard box brass, your risk the chance of a carbon ring. The ring may not only make chambering difficult, but also cause an upward and inconsistent spike in your velocity. Dave Kiff has addressed these very problems on this board. Your waterline vertical is shot at 600 and 1000 and your groups and scores will suffer, i.e., your competition package is not as good as it could be if you did your homework.

If you want to shoot a no turn chamber, or neck turned brass or a chamber cut for about .002 clearance allowing your to shoot no turn or neck turn to no more than .004 clearance, you need to know the thickness of the necks before your start.

John is correct about obtaining as much of the new brass as you can before you spec your reamer. I was just asking for info to see if it ran parallel with what I already have. There is as much to the spec of a custom reamer as there is to a custom size die. If you blow the reamer issue, you blow the custom die because the total package does not fit the base, shoulder and bump of your brass. I have a great 6BR reamer and custom die for the old brass. It is no longer "custom" for the blue box brass.

Thanks again for your point of view Terry as I have always found this to be an interesting subject. But, I am still looking for the dims on the blue box.

Jim Hardy

 

[brshtr]

Jim,

I bought some blue box Lapua 6mm BR Norma brass last fall. I measured the necks on 10 cases, five from each of two boxes, measuring each neck in four places. Of the 40 measurements, the thinnest was .0124" and the thickest was . 0134. Most were in the range of .0124 - .0129".

I also measured 10 cases from each box for length. One box ranged from 1.555 - 1.558". The other ranged from 1.554 - 1.557".

Hope this helps.

Dave Rabin

 

[johara1]

Jim, if you are going to leave it a 6BR. and if you plan to turn necks is an other question. i have a lot here that is running 1.555 in length and the neck is .011 thick. Flash holes are all over the place in diameter and some primer pockets are really loose. You have to learn to dance with these new ones.
If you are planning a Dasher i can help you on that one……. jim