Does anybody know what the tap/thread size is? I have the guage but apparently they don't make a modified case for the 280AI. Does anybody know the tap size they use so I can make my own modified case?

5/16x36

Another option is to send Hornady a case and they'll machine it for you. Cost is nominal. If you neck size only, you can send them a once fired case for even greater accuracy.

They do this oddball size on purpose for force you to buy their cases. Good luck finding a 5/16-36.

They're available from the big tool supply houses. I got mine years ago from MLCS and I've seen others post their availability at other places as well. They aren't unique.

Here is one for under $8 shipped.

http://cgi.ebay.com/ws/eBayISAPI.dl...temid=300421295852&ff4=263602_263622

Took about 15 seconds to find.

i just bought one.

The trick is how to get a straight drill and tapped hole in the case. I drilled many of the differnt cases crooked for a while till I came up with a plan. I don`t own a mini lathe so it was consuming me to find a way that I could do it myself without bugging someone. I have a neck turning tool from Sinclair that came with v-block handles (these can be bought separately) that I clamp to the case and drop it through the table on my portable drill press. It has to be held with channel locks to keep it in place. Its crude at best but is the best option I have found so far. I can get great results with no discernable runout.

WTH, I did too.

Anyone doing this, will no doubt, gain much appreciation for the toughness of the brass case. Especially Lapua.

Nice low tech solution Tim.

What size drill bit did u use?
757

9/32" is specified.
Some say 19/64"
Some say letter M

Any of the above would work fine for this application.

I ordered the tap and correct drill bit together. I`m pretty sure 9/32" is the right one. The original bit has dulled some and I am using an alternate and the size was not exact, and worked just fine. I used mic to measure the drill bit shaft to compare.

Wow- you dulled a drill making holes in brass cases?? Time to upgrade your drills!

Nice solution though- I am spoiled as i put them in the 3-jaw and drill away. I have drilled dozens for the stuck case remover but it is usually 1/4-20 or 1/4-28- still tough to rip through.

What is the process for opening up the necks to accept the bullet and does the case need to be sized or in its original fired shape?

You can use FL or new brass if you have an expander such as one used pryor to neck turning. If not a once fired case would be a prime candidate. You would just deprime only with no sizing to the neck.

I just tried this and it is a PITA to try and keep the brass stationary without bending the brass....Think I'll see what Hornady charges to make one from a fired case.

Hornady charges $14 and requires you to pay postage both ways (you must send self addressed stamped envelope for the return).