Help with my math

[kyreloader]

I recently bought a .284 Win prefit with a 0.312 chamber. I am doing math to figure how much a need to turn off the necks of my new Lapua brass.

I was planning on overall loaded neck diameter of .308 or .309 to give 3-4 thous clearance(any preferences on amount of clearance works best?). Therefore, 0.309-0.284=0.025/2=0.0125 thickness per side? So if I turn to 0.0125 or 0.012 I should be good to go?

Thanks for advice on neck clearance and checking my math!!

 

[expiper]

Dear KY,,,,your math is fine,,,,and,,,,.003-.004 is good clearance,,,,Roger

 

[22BRGUY]

Dear KY,,,,your math is fine,,,,and,,,,.003-.004 is good clearance,,,,Roger

Same as I got also.

 

[kyreloader]

Follow up question?

I have the ability to turn the cases as 6.5mm before I neck up to .284 or after I neck up to .284. What is the consensus of the forum, turn to thickness before or after I neck up?

Thanks again.

 

[Steve Blair]

Expand neck, then turn.

 

[P1ZombieKiller]

Follow up question?

I have the ability to turn the cases as 6.5mm before I neck up to .284 or after I neck up to .284. What is the consensus of the forum, turn to thickness before or after I neck up?

Thanks again.

This answers the "do I size up and turn, or turn them size up question"..... In your case, you are only oing up .020 and not .060, but the results are the same.


http://forum.accurateshooter.com/index.php?topic=3833425.0

 

[Kodiak99317]

I have a .312 chambered 284 as well and I turned my brass to .0126. The loaded rounds after turning measure .310. If you want .309 loaded rounds, you should turn to .0122
My theory is that there is .0004 of an air gap from the bullet to inside neck wall since .0126*2+.284 s/b .3092 but they all measure .310 loaded with 180g VLD Berger

 

[Keith Glasscock]

Might be a good idea to measure the pressure ring diameter of your bullets. They can vary a little and throw your calculations off. Another option is to seat a bullet in the first one you turn and give her a check.

As a safety measure, I use a sizing bushing matching the diameter of the chamber (or .001" smaller) as a final check of loaded rounds. If the bushing goes with ease, you're good.

 

[kyreloader]

Follow up question?

I have the ability to turn the cases as 6.5mm before I neck up to .284 or after I neck up to .284. What is the consensus of the forum, turn to thickness before or after I neck up?

Thanks again.

This answers the "do I size up and turn, or turn them size up question"..... In your case, you are only oing up .020 and not .060, but the results are the same.
http://forum.accurateshooter.com/index.php?topic=3833425.0

From that thread, neck up to .284 then turn.

Thanks.

 

[kyreloader]

Expand neck, then turn.

Thanks Steve.