Neck Diameter

[Twud]

How can I measure the inside neck diameter of my 22-250. Is there a tool that is made for this purpose. Starting with some new brass and bushing dies.

 

[tightneck]

A cerrosafe cast is probably the best way. A fired case will give a pretty accurate guess though. The neck of the case will usually spring back about .001 after being fired, so the chamber is about .001 larger than what you measure.

 

[Forum Boss]

If you mean measuring the actual inner diameter of the gap through which the bullet passes in your cases, that changes before and after sizing. If you are trying to gauge how much neck tension there is on the round, measure the neck after sizing, then use a ball micrometer to measure the neck wall thickness.

If, for example, the neck OD is .267" after sizing, and the neck-wall thickness is .014", then the interior diameter,after sizing) is .267-,2 times .014) or .239. That means there is .004" tension on a .243" diameter bullet.

Check our bulletin. RCBS has a new Ball Mic that is under $45 from Cabelas.com

 

[anyrange]

I use gauge pins. I have one chamber with a .245 neck and a .246 gage pin fits into it. Gage pins work great for measuring inside of cases also.