Neck turning; take me to school

[pyroducksx3]

It turns out I have to turn the necks on my norma brass because I need some clearance in the chamber. My loaded rounds are .313 and I need to get them down to .309. Whats the best way and tools to accomplish this. I have an RCBS trimmer pro and know they have an adapter for that but just not sure what the best method is. Thanks.

[royinidaho]

Neck turning is always a fun topic.

Two approaches are available.

Outside neck turning and inside neck reaming.

For a hunting rifle and simplicity I prefer reaming. For benchrest/target application I use neck turning.

Tool recommendations would be: Sinclair for turning and L E Wilson for reaming.

BTW, I only do either when absolutely forced to. As in your case.

[pyroducksx3]

This s a "hunting" rifle but it is a semi custom. Im not against either method, the inside neck reaming will get me there? I only need to do this one cartidge , a 7 rem mag, so I dont think I will need the whole sinclair kit, that should bring the cost down right? If I choose to go that route (Outside) Thank you

[royinidaho]

Snoop around that is, google on neck turner.

The are all more or less the same. Prices vary all over the place.

Here is Hornady's offering: Neck Turning Tool

Regardless of which provider you choose, only a 7mm mandrel will be needed.

Neck turning will give you more control neck tension. Reaming will result in consistent neck tension but will not ensure that the precise amount of material that you need to be removed will be removed.

With turning care needs to be taken to ensure a "donut" is not formed a the base of the neck. Care must be taken to ensure that you stop exactly at the shoulder. If you stop before the shoulder the ridge left will transfer to a ring on the inside when the case is fired.

When the shoulder is cut into the shoulder is greatly weakened.

After/or before turning, trim all cases to the desired length and chamfer inside and outside of case mouth.

Warning!!! Don't take too much off. It can't be replaced. I know that for a fact.

[Bullet bumper]

Inside neck reaming has limitations in as much as you only have one size in each tool and that is the reamer . So if you buy the wrong reamer or the case necks change in thickness due to a different batch , then you don't have the right size.
Outside neck turning is way more flexible as you can adjust your cut for any case neck thickness .
You can cut down on the shoulder with just a slight skim that just marks the shoulder it will not weaken the case . I have done it thousands of times or more with no problem .
A dedicated Sinclair neck turner works good and I like it better than those adaptors that go in case trimmers .
If the gun is used for hunting then some clearance in the neck is required as it only takes a small bit of rubbish like an unburnt granule of powder to jam the round and stop it chambering.
If you have to neck turn then I would consider partial neck sizing using a bushing or collet die and then body sizing with a body die. This separates the two jobs so full length sizing will not be required . Avoid expander ball sizing dies as they just screw up the turned neck.
Most 7 mm Rem mag chambers have approx. a .317 neck so are you sure that the .313 neck diameter round does not fit because of the neck and not some other part of the case .
What is the neck dimention in the custom chamber ? It might be marked on the barrel .

[pyroducksx3]

Its a custom chamber, and its .314

[pyroducksx3]

Sinclair 1500 neck turning tool on order