Chamber length and trimming

[lejuch]

Ordered and received Sinclair chamber length measuring tool.

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i have determined my 338 Lapua Magnum chamber is cut 2.760, while my Sierra Reloading Manual specifies this dimension should 2.724(I am assuming they are just reprinting SAAMI specs). Trim length specified in manual is 2.714 which would allow 0.010 space for case length. Given my chamber length is significantly longer at 2.760 leaving 0.046 space for case length, what ramifications should I expect to run into, if any? Shoulder length/head spacing is within spec, just overall case length in chamber is too long.

 

[rsmithsr]

this is a typical over length neck..its a safety feature.
I would trim to 2.745 and retrim anytime you hit 2.755.
I personally run much closer on target rifles.

 

[Mikecr]

Now that you know your chamber length, the manual information is useless, right?
It was always useless, right?
Desired trim length for me is at or within 10thou of chamber end. I wouldn't retrim until cases went well under 5thou of chamber end. But that never happens to me(I don't FL size). My cases shrink in OAL at first, and then grow very little, very slowly, until settled.

Excess chamber end clearance, like excess neck clearance, allows carbon to gain momentum rearward. This, affecting consistency of neck sealing and building of a carbon donut that acts to reduce clearance. It's hard to manage an ES of <10fps without controlling these clearances.

 

[243winxb]

2.7504" looks like the chamber length? Does leave a lot of room for case length growth. SAAMI is .026" from case mouth to chamber end. Clean like its a Weatherby.