Chamber Neck Length?

[Lonewolf74]

So I got one of those Sinclair neck length guages, it's basically a plug that you seat into a case with the neck trimmed short. Then you load it into the rifle and it will get pushed back giving you the neck length of your chamber.

I did it on my rem 700 300 wm that was trued and the chamber recut. What I got was 2.671. The book max case length is 2.620 and trim to length is 2.610. So my chamber neck length is .051 longer than book max length.

My question is does this seem excessively long and should I try to get my case neck length up to 2.650 or something like that?

 

[can1010]

quick design has that length at 2.644. if your plug isn't the exact same dia. as your neck you will get a false reading

 

[Mikecr]

I'm thinking the inserted measuring neck/plug would not be centered so well as to enter beveling of chamber end(as loose ammo usually isn't), and would contact at beginning of actual chamber end. You can try it 4 or 5 times and if any readings are shorter, then your that much closer to nailing exact chamber end.
If you don't mind try that & let us know.

It does not surprise me that YOUR chamber is considerably different than published. Hence the utility of this tool. Sinclair:
This measurement will tell you how much excess case length your chamber may have over published trim lengths in reloading handbooks.
The differences between published trim lengths and the actual length of your chamber can be quite significant. You could be over trimming your cases by .030 inch or more.

 

[AZShooter]

It is quite common to encounter chamber ends that are long. In fact every factory chamber I have measured were well past the max SAMMI OACL. No need to ever trim for the life of some cartridges as the case would wear out before the neck would impinge on the end of the chamber.

IIRC I first read about this on Varmint Al's website in the late 1990s. He was an engineer and has written some interesting stuff. His information is still relevant today. Regarding chamber length, quote: "I usually find that the factory recommendations for case length leave a 0.050 inch to 0.070 inch gap between the end of the case and the actual length of the chamber."

Varmint Al's reloading pages http://www.varmintal.com/arelo.htm#Chamber_Length

He has a section on the mini lathe. Within it he included how to machine your own chamber plugs. I made my own on my lathe saving time and money. Thanks again Al.

http://www.varmintal.com/alath.htm#Chamber_Length_Gauge