Case Length NEWB question

[toliver]

Let me start by saying I have been creeping around the forum for awhile and have quite enjoyed the info and humor though not participating. I have one of the 1990's Winchester Mod 70 heavy stainless in .308. Shoots federal 168 smk's factory ammo like crazy good. I was prepping some cases last night as I have a bunch of Bergers I'd like to try out. Most of the brass was measuring 2.010 with a few odd balls in their +/- .003 or so. Manual I looked at said trim length 2.005. I did that so they would all be the same, thats fine, but got to thinking as my ocd kicked in. Just how long a case could my rifle use before I needed to trim. Seems the longer it is the better as long as its within spec to the chamber? Well I used a sinclair chamber length tool, the one you cut a case back and insert into the mouth, chamber, then measure. My result was 2.039 consistently. So are these normal measurements as far as a chamber may be concerned? Will brass eventually stretch that far before failing? Don't really know why it bugged me but it just seemed like a long way? I suspect its to keep people from loading cases that are to long and having big problems, I sort of wish my brass was longer if that is my chamber dimension? Or should I just forget about it and keep doing what I'm doing as long as it shoots good.

Thanks Folks

 

[FearNoWind]

The SAMMI specs I assume you're referring to for your case length are commonly accepted industry standards. Companies that commercially manufacture and market rifles will typically chamber them a little longer and wider in the neck region to accept a wide range of ammunition. A custom made rifle will usually be chambered with a custom made reamer and the tolerances will be much closer.
If you have a rifle that shoots good as it is you're better off to leave it alone, feed it what it likes, and enjoy using it.

 

[Outlaw6.0]

^^^ I agree.


When prepping a new batch of brass, I tipically measure all of my pieces & trim the to the shortest (usable) length. If memory serves me correct, .003-.005 longer than the books "trim-to" length. The extra neck length has never hurt me, even in some of my $$$$ customs.

I do this mostly because my rifles tend to run on (or over) overbore, I'll take all the neck length I can get. The .308 is so forgiving, the extra .003 will make no difference over standard trim-to length.

t

 

[Dosh]

Toliver, if crazy good is good enough, stick with it.

 

[MagnumManiac]

You are correct in thinking that there is a built-in safety margin in your chamber, it is usually set around .035"-.040" longer than the trim-to length, as you discovered.
ALL chamber reamers have about the same amount, whether custom, match or standard.
I have only ever run into trouble once, in my 25-06, cases were .050" longer than MAX CASE LENGTH, fired ONE cartridge, gas and smoke came out of the bolt raceways and the bolt was locked SOLID, eventually got the action open, no primer to be found! The case had a very swollen head and where the case mouth was pinched was quite discernible.
I do have this case on my loading bench as a reminder to ALWAYS check my SIZED cases for length, I have a photo of it, but can't post pics from my tablet for some reason.

Good shooting to you.

Cheers.
gun)

 

[Edd]

Let me start by saying I have been creeping around the forum for awhile and have quite enjoyed the info and humor though not participating. I have one of the 1990's Winchester Mod 70 heavy stainless in .308. Shoots federal 168 smk's factory ammo like crazy good. I was prepping some cases last night as I have a bunch of Bergers I'd like to try out. Most of the brass was measuring 2.010 with a few odd balls in their +/- .003 or so. Manual I looked at said trim length 2.005. I did that so they would all be the same, thats fine, but got to thinking as my ocd kicked in. Just how long a case could my rifle use before I needed to trim. Seems the longer it is the better as long as its within spec to the chamber? Well I used a sinclair chamber length tool, the one you cut a case back and insert into the mouth, chamber, then measure. My result was 2.039 consistently. So are these normal measurements as far as a chamber may be concerned? Will brass eventually stretch that far before failing? Don't really know why it bugged me but it just seemed like a long way? I suspect its to keep people from loading cases that are to long and having big problems, I sort of wish my brass was longer if that is my chamber dimension? Or should I just forget about it and keep doing what I'm doing as long as it shoots good.

Thanks Folks

All of your measurements are normal. The SAAMI minimum for a case is 1.995" and the maximum is 2.015". The SAAMI minimum for the chamber is 2.025" and the maximum is 2.040".

Based on these numbers, a difference in the case and the chamber length anywhere between .045" and .010" would be within the specs.