Overall case length

[azhank]

.308 Win Lapua brass on its 5th round of firing. The brass has not been trimmed, but has been neck turned. I know that the max length is 2.015. Currently, my 100 cases are ranging from 2.000-2.009.

Is it normal for this brass not to lengthen?

Should I trim them all down to 2.000 for uniformity?

Is there anything wrong with the idea of have this short (2.000) length?

 

[azhank]

Re: Overall case length

I have been only neck sizing since fire forming them.

 

[azhank]

Re: Overall case length

hmmm. I have been doing some reading and came across a trim length of 2.005, but not a minimum length.

 

[Fuzzball]

Re: Overall case length

There is no "over all case length"; there is a case length and there is a cartridge over-all length, expressed as either OAL or COAL; both mean the same thing. You won't see a "minimum case length" anywhere because there isn't any such specification. What we see in most manuals as a "trim-to length" is simply an arbitrary 10 thou less than the max case length.

 

[azhank]

Re: Overall case length

Do you see a problem with me trimming all my cases to the shortest length of 2.000?

 

[Greg Langelius *]

Re: Overall case length

No, but case length is one factor in generating neck tension, so keep such things in mind.

Also, excess case length can cause a case to jam into the throat and cause severe pressure spikes.

Greg

 

[jagged77]

Re: Overall case length

Often times neck only sizing won't grow the cases too much - FL or body sizing however tends to squeeze the body back a bit and the case grows a bit taller.

You are better off trying to get a case OAL measurement for your chamber - you can make a poor man's gauge or go and buy one. Failing that just trim the ones that need it to a known safe length (2.005") and keep them there letting the others catch up.

My Rem 700 SPS tactical (factory barrel) measures 2.030" - therefore I can let my case grow to 2.020" if I want.

 

[bowm0051]

Re: Overall case length

You should be ok going to .020" under max length. If you look at the instructions of a RCBS X-Die, that is what they want you to trim to.

 

[Fuzzball]

Re: Overall case length

"You should be ok going to .020" under max length. If you look at the instructions of a RCBS X-Die, that is what they want you to trim to."

Yeah. And that amuses me! Few of us ever trim 20 thou off our cases before tossing 'em, meaning that the costly X-die is a gimmick with no valid application!

 

[bowm0051]

Re: Overall case length

That is exactly what I thought when I read it too. Does it really even need to do anything if you are already .030" from trim length? Not sure how many times I would need to fire .223 to get that about of growth.

 

[RotARy15]

Re: Overall case length

Do-it-yourself chamber gauge.

Slowly chamber it, remove and measure.

Repeat 3 times to be sure. This will give you the absolute maximum case length. Trim to at least .010 short of this measurement.

To make it, simply cut the neck of a sized or gently sized case in half. Clean up the case and the ring.(You can use case prep tools for this) Seat a bullet in the case deep enough to keep it off the lands and place the brass ring over the bullet. Remember: Size the case before cutting.

I did this with a case that I neck sized using a Lee Collet die. This helped because it allowed me to squeeze the neck down just enough to be able to partially seat a bullet by hand. This sizing method is the same one used to make a do-it-yourself COAL gauge.

ETA: Just so you don't question your measurement, my chamber measured out to 2.035. I would trim to 2.025. Notice the word <span style="text-decoration: underline">would</span>. I have yet to actually grow to this length. Your chamber length may vary.

Don't over think the uniformity thing. Unless you are shooting benchrest, .010 difference won't be noticeable.

 

[FLIGHT762]

Re: Overall case length

Interesting thing to do is actually measure your chamber's length. I used a Sinclair chamber length gauge on my two 308 Win. bolt L/R guns.

It was interesting to see that the chamber length on my Remington Custom Shop 40 XBKS is 2.845" and my custom Palma chamber is 2.840".

So much for worrying to obsessing over trimming to well under the 2.815" SAAMI max.

 

[boltgunluvr]

Re: Overall case length

One will usually see it listed as "maximum trim length" which refers to the shortest recommended case length after trimming....it can get a little confusing to newbies.