Tightneck 6-284 question

[wildcat]

Hey guys, I am having a 6-284 built and I want a tightnecked chamber. Can you guys give me any suggestions on the diameter I should use. I was thinking .268 or .270. Please, I need help, and I know many of you have experience with this chambering.

Thanks
Wildcat

 

[winmagman]

Wildcat
You planning on neck turning or not? If your not neck turning you might want to stay at .276-.278, if your going to turn .268 or .270 would be fine since you can turn off however much brass you need to fit the chamber(to a point).

The 6.5-284 Lapua brass I've got has .014-.015 neck thickness, necking down will probably thicken it up a little bit so you would be at a min. .273 with no room for expansion to release the bullet, bad juju.

Hope that helps some
Chris

 

[uncleB]

If you are having a new reamer made go with a .272 if you are using Lapua or Norma brass. if you go with a .268 you gain nothing but spend your time neck turning instead of shooting.
UB

 

[Fiftydriver]

I would agree with UncleB on this one. If you use quality brass like the Lapua hulls, and are designing the reamer for your project, I would not recommend doing a tight necked chamber. That being one that required you to cut 2 to 3 thou off the thickness of the neck.

Now taking a very light truing cut just to even up the necks is one thing but this can generally be done by only taking 1/2 thou off the neck thickness.

If you have never turned necks before I would highly recommend you go with a chamber design so you do not HAVE to turn your necks. Again, get some dummy rounds loaded up and take some neck diameters and go from there.

One thing many do not realize with a really tight necked chamber in a round such as the 6-284 is that you really have to watch neck hardness from fire hardening. They can split very easily once the case necks get a few firings on them even if they are not oversized.

This is simply from the thinness of the neck getting brittle and cracking. If you anneal your cases every 3-4 firings this is really not a concern but again, another step.

Long ago I had my first true long rang rifle build in 6-284. This was long before I got into building rifles professionally and the smith I was using recommended a VERY tight BR style neck in my chamber. It was cut to only 0.265" in diameter which ment alot of neck turning since there was no such thing as facotry 6.5mm-284 brass then. I was using the old 284 WIn cases and still do to be honest!

The rifle is a dream to shoot, a legit 1/5 moa rifle at 500 yards and in good conditions and if I am up to it, a 1/2 moa rifle at 1000 yards.

Still, since I have started building rifles, I have build alot of 6-284s and I designed my reamer to require no neck turning using Lapua cases and they will also match this accuracy level and case neck life is dramatically longer without annealing.

If your used to turning necks then have at it if you want to but its alot more work then most realize until they get into it and in my opinion, the advantages of a tight neck chamber are over rated inmost cases with the quality of todays brass such as Lapua and Norma hulls.

Good shooting!

Kirby Allen(50)

 

[wildcat]

Fifty and Uncle B, thanks for the info. I neck turn my 6.5x284, and I like doing it, so I don't mind neck turning. I am leaning towards the .272 neck diameter suggested by Uncle B. I will be using Lupa Brass, so will it be worth it to have a tightneck 6-284. I want to get the most accuracy out of this rifle as possible. I do lots of prep work to my brass such as cleaning flash holes, uniforming primer pockets, checking for runout, sorting by weight, ect. So, I really don't mind neck turning. Will neck turning the 6-284 give me an edge in the accuracy department, and is the .272 neck diameter the way to go.

Thanks
Wildcat