Case length vs chamber length

[Headgear]

I just got some new Lapua brass and have a GAP built Surgeon, Mike Rock 308 custom. I also just got a Sinclair length gauge and want to set up my trim length for my chamber. The instructions with the gauge warns to maintain at least .024 less than the chamber length.

I am hand feeding, not through the magazine. For the best long range accuracy, how far back should I trim them?

 

[427Cobra]

Re: Case length vs chamber length

.010 is a good place to start, but it might take a while for the brass to grow that far if it already has rounds down the tube.

 

[ChadTRG42]

Re: Case length vs chamber length

I would not trim to less than 2.005". If it is new brass, don't worry about trimming it. If it gets longer than what your chamber will allow, note that length, and trim to .010" or .020" shorter than that length. Most 308's will allow for more than spec case length.

 

[Fuzzball]

Re: Case length vs chamber length

"The instructions with the gauge warns to maintain at least .024 less than the chamber length."

 

[427Cobra]

Re: Case length vs chamber length

That number must have come out of a Lawyers ass, Victor will come along soon and say he does .005 on his match BR guns

 

[Victor N TN]

Re: Case length vs chamber length

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 427Cobra</div><div class="ubbcode-body">That number must have come out of a Lawyers ass, Victor will come along soon and say he does .005 on his match BR guns </div></div>

Yes I trim to max -.005" on my bench guns. But for everything else I trim to max -.010" Max -.005" will get real tight if you have shot a few rounds and get carbon fouling. That's why I trim field gun ammo to max -.010"

But it's your rifle and your ammo. It's basically your choice and your decision.

 

[pawprint]

Re: Case length vs chamber length

Load some new brass, several sizes, as mentioned, you won't get true fireformed brass until at least two firings (neck size only). Mic everything, before and after, after several firings, you'll know "exactly" what your chamber is doing, your best trim-etc.

 

[blue_ridge]

Re: Case length vs chamber length

Say you've gone through several firngs with new brass and you have brass ranging from 2.012 - 2.020? Do you sort by length and trim only the longer cases?

 

[Victor N TN]

Re: Case length vs chamber length

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: paw print</div><div class="ubbcode-body">Load some new brass, several sizes, as mentioned, you won't get true fireformed brass until at least two firings (neck size only). Mic everything, before and after, after several firings, you'll know "exactly" what your chamber is doing, your best trim-etc. </div></div>

The reason I trim my rifle brass as long as I can is not for group accuracy. (At least not current groups.) It's to preserve the accuracy in my chambers throat. Excess trimming of the brass will cause the hot gasses under pressure to act like a cutting torch against your chamber where the end of the brass is located. The chamber throat is only exposed to these gasses a few nano-seconds. But over time it will do damage to the chamber throat.

At this point I would like to point out that if you are loading for more than one rifle of the same caliber, cutting the cartridge brass long MAY cause a problem in the second or third rifles. But no more so than setting the dies to one specific chamber. I have seperated my brass / ammo and labeled for each rifle.

Once again, to trim long or not, is your personal decision.