Need to make a core seating die.

[just bill]

As I continue to recover my Swaging dies and jacket dies for my .308, it appears I don't have a core seating die. I need to find out the ins and outs of the die body. I can either drill and polish/lap the the hole through the die body or bore which could be challenging due to the small diameter of the hole. Where I fall short the correct way to lap and what diameter to start lapping. My guess would be work up to a "Q" drill bit then start lapping. Any advice would be greatly appreciated since ALL web research died in the computer crash.
Thanks, Bill

[garandsrus]

You want the core seating die hole to be .307 to .3075. Each die will enlarge the bullet by a small amount, ending with the pointing die at .308.

A Q drill is way too big at .332.

[just bill]

You want the core seating die hole to be .307 to .3075. Each die will enlarge the bullet by a small amount, ending with the pointing die at .308.

A Q drill is way too big at .332.

Thanks, misread the drill chart. I need the lapping procedure. I had some kind of instructions using wooden dowel and finishing forceps, however it’s lost in the world wide Webb.

[garandsrus]

You would probably be just fine reaming the hole for the core seat die, assuming you can get the correct reamer size. To lap/polish the die, I use a split brass rod with sandpaper and oil. I stop at 400 or 600 grit.

I Found this: https://www.maritool.com/Cutting-Tools-Reamers-HSS-Chucking/c78_262_263/p4522/.3075%22-HSS-Reamer/product_info.html

[just bill]

You would probably be just fine reaming the hole for the core seat die, assuming you can get the correct reamer size. To lap/polish the die, I use a split brass rod with sandpaper and oil. I stop at 400 or 600 grit.

I Found this: https://www.maritool.com/Cutting-Tools-Reamers-HSS-Chucking/c78_262_263/p4522/.3075%22-HSS-Reamer/product_info.html

Thanks

[Rabie]

I found that with my 308 dies, the point forming die is about 0.001" smaller than bullet as you habe springback from copper. The easiest way with the least amount of effort is to build yoir die drill a small hole straight and through. The get the die hardened. Once hardened get someone to EDM Wirecut the die for you. They can keep to tolerances of 0.0004". And it leaves very little that needs to be lapped.

[chuck curry]

That is way to big for a Coe. The core has tob smaller than the jacket to go inside it. You are talking jacket diameter not core diameter.

[chuck curry]

Thanks, misread the drill chart. I need the lapping procedure. I had some kind of instructions using wooden dowel and finishing forceps, however it’s lost in the world wide Webb.

You want the core seating hole to be .307 to 307.5. The core needs to be much smaller than this to fit inside the jacket. The core seating die for my Corbin press is .243. .307 to 307.5 would be the bullet diameter after core seating.

[deltaenterprizes]

Reamers are readily available and priced right on eBay!
I just picked up 2 reamers for about $15 delivered to make a replacement part for a core mold.
Don’t forget to check metric sizes, some are between fraction, letter and decimal sizes.
The one that I needed is 5.6 mm.