Shoulder / Neck Junction Radius

[pdog]

I am working on a 6.5 mm wildcat and have most of the details worked out but am not sure about the radius at the shoulder neck junction. I have seen radius on existing cartridges from .060 to .125. Any advice or reasoning as to what radius would be best?

Thanks in advance for your input. pdog

 

[dkhunt14]

Are you sure you don't mean angle? Matt

 

[CatShooter]

I am working on a 6.5 mm wildcat and have most of the details worked out but am not sure about the radius at the shoulder neck junction. I have seen radius on existing cartridges from .060 to .125. Any advice or reasoning as to what radius would be best?

Thanks in advance for your input. pdog

Older cartridges (30-06) have 0.10 - 0.125 r as a shoulder/nec junction and 0.050 to 0.10 r as a shoulder/body junction.

Newer cartridges (284) have 0.05 - 0.10 r as a shoulder/neck junction and 0.030 to 0.060 r as a shoulder/body junction.

Keep in mind that these radius' are set with the ability to be practical to mass produce in mind - if you are making your own specs and blowing your own cases, then you can use very small radius', down to sharp enough to shave with... the less the radius, the less the case growth when sizing.

 

[dkhunt14]

Whenever I ordered a reamer I was never asked about a radius. All they wanted to know was the Diameter at the .200 line which is very important. The amount of freebore which is also important. Matt

 

[johara1]

I think i would call PT&G and talk to the guy that makes reamers ………. jim

 

[expiper]

OP,,,I like that radius to be .060"....it prevents brass flow (sorta like a 40 degree shoulder),,,,Roger

 

[Changeling]

OP,,,I like that radius to be .060"....it prevents brass flow (sorta like a 40 degree shoulder),,,,Roger

If .060 at the neck/shoulder junction prevents brass flow, does that mean there is NO chance of a doughnut with that case design measurement in your opinion? Just a question.

 

[BoydAllen]

The smaller radius will help to prevent brass "flow" (not really what happens) but it will not prevent doughnuts. Gene Beggs' two calibers, that are based on the .220 Russian have .060 radaii for that reason. The stock .220 Russian radius is .120. Smaller radaii are not a new idea. It is just that specifying them is often overlooked. If you look at the drawing of the 6mmBR Norma on this page, http://www.accurateshooter.com/cartridge-guides/6mmbr/ you will see that the radius is called out. Other reamer drawings that I have seen have not included that dimension.

 

[pdog]

Thanks everyone for your help. I am leaning toward .030 radius on the body shoulder junction and .060 radius on the neck shoulder junction. Basically copying the 6br radius.
pdog