correct inside neck diameter

[rudyc]

Hello,

I am forming some 8x57rx360 cases from 9.3x72r brass.

When I finish the new brass the inside neck diameter is around 0.304-0.305.

The jacketed bullets I'd like to use are 0.318.

What should I be reaming the inside neck diameter to??

I am going to be ordering a reamer from Forester.

Thanks in advance,

rudyc

[stimpylu32]

rudyc

That will depend on the thickness of your case neck as to which reamer you need , your going to want to keep the neck thickness at around .007 .

What does your outside measure now ?

stimpy

[rudyc]

Inside mics 0.306, outside mics 0.335. The leaves nearly .030 difference, however when I try to measure the thickness of the brass at the neck I'm getting 0.011 - 0.012

rudyc

[stimpylu32]

rudyc

I take it that you have run these cases through a 8x57 FL sizer die , Do they chamber OK in the rifle ? If so I'd go with a stock .311 reamer to start , before spending the money for a custom ground one , that should take the wall down to around .009 thickness .

Also you may need a diffrent expander ball for your FL sizer , around .314 should work well .

stimpy

[Graybeard]

Generally speaking you want the ID to be about 0.002" to 0.003" less than bullet diameter for a tight hold on the bullet. In your case I DO NOT think reaming is the way to go. I suspect what you really need is a different size expander ball as Stimpy mentioned. You have to be correct in both ID and OD and I seriously doubt you have enough case wall thickness to ream for the needed ID and still have any brass left in the neck.

[rudyc]

Ran them through an 8x57r/360 FL die from C&H. After trimming to the correct length they chamber fine, that is, until I seat a bullet, then they won't chamber.

After using the .316 expander die and seating the bullet, the outside neck diameter is 0.346. Still won't chamber. I believe I can turn the outside of the neck about .002 - .003 per side and get the results I need.

[stimpylu32]

rudyc & GB

If you were to run the .311" reamer in while the case mouth is still at .306 that will take .0025" off the case wall on each side with out having to do the work of outside neck turning , as your using a Forster trimmer this can be done while you trimming to length , I do it all the time , works great .

With the bullet seated you should have an OD of around .340" and that should chamber for you ok .

stimpy