.308 fired brass dimensions

[rocknut]

So I just pulled some of my nice clean Lake City Match brass out of the tumbler after fire forming them to my new Savage rifle. I got out my trusty Lyman case gauge and dropped a few in just for grins. The cases drop in all the way but maybe an 1/8 of an inch. Most will even go nearly all the way with a little finger pressure! These cases have not been sized in any way. My last .308 rifle would leave pretty much the whole neck length outside the gauge which makes sense. I neck size for the most part and that is all the cases usaully need. Is this just a sign that the chamber was cut with a tighter neck diameter? I checked standard reamer prints, they call for a .3435 neck. A match chamber would be .3415. My brass is measuring .344 after firing. This is a Shilen chambered barrel. Anybody else run into this situation?

 

[bigedp51]

Case gauges are made to measure from the shoulder of the case to the base or cartridge case headspace length. If you turn the gauge upside down the fired case neck should enter the gauge meaning the neck isn't hampering the fired case from entering the gauge.

The fired case doesn't enter the case gauge all the way because of body diameter. Resize the case and it will "fall" into the gauge until the shoulder of the case contacts the shoulder of the gauge.

Bottom line your fired cases do not fit inside the gauge because some of the cases have a fat A$$.

 

[rocknut]

Thanks for your thoughts BigEd. Maybe I didn't make myself clear. These are fire formed cases. I only resize the necks for the next 4 or 5 cycles. Then I anneal and full size to bump the shoulder back if it needs it. I can't quite get the cases to enter the gauge from the bottom as you suggest. I can completely chamber several of these unsized cases with no resistance. I'm thinking that my new chamber is so tight, not only is the shoulder not moving forward at all, The neck is hardly expanding as well. I'm used to collet sizing the neck to get the case to drop the last 3/8 of an inch into the gauge. I can get these unsized cases to fit in my gauge with just a bit of finger pressure if even that.

 

[bigedp51]

A case gauge is used to measure full length resized cases, I do not have any Wilson cases gauges that a fired case will fit 100% of the time. Again your cases are not going to fit correctly because of body diameter.

Bottom line, it is not a fired case gauge, it is a full length resized gauge. As you said the case was fire formed to YOUR chamber and not a case gauge. If you just want to measure base to shoulder get a Hornady gauge.

Below a fired .223/5.56 case resting in the Wilson case gauge, to is too fat to drop in any further.

When you neck size the Hornady type gauge is the only way to measure cartridge headspace and shoulder bump.

 

[johnu]

I have a Tikka in .308 where the fired cases are essentially the same size as full-length sized ones - it's very accurate.

John

 

[Shynloco]

Might I suggest you try running those LC Cases through a Body Die or a Small Base .308 die. I recently did testing with a bunch (300+) of different Lake City Brass including LC National Match and LC Match from a number of years all the way back to 1966) during which I had to run some of the brass through one or the other die. BTW, the purpose of my testing was purely curiosity and to see if LC Match brass could keep up with my Lapua brass in a Benchrest .308. Though 1977 Match shot very close, even it didn't shoot as well as the Lapua brass in my particular rifle. But those dies I mentioned cured any of the ills in terms of body dimensions so they'd fit smoothly into either my Wilson Case Gauge or my rifle's tight chamber.

Alex

 

[rocknut]

Thanks for your thoughts Alex. I full length sized these cases after I annealed them. They fit my chamber very well thanks. I am using regular lake city stuff that I know has been thru a machine gun. I always check these very closely for concentricity or a bulge at the base after full sizing. If there is any that won't fit my case gauge easily or are out of concentricity when I spin them, I recycle them. I have run into some that simply would not full size properly, those get recycled too .I might have been able to save some of them with a small base die but, hey; I basically got them for free by exchanging range brass for those cases. The batch of Match cases I'm working with now are all quite straight. I thought they where a little on the stiff side when I resized them, even after annealing. I haven't weighed them, but my guess is they are heavy. They were made in 1966. They appear to be very well made.
To get back to my original post. There is nothing wrong with the brass. It just appears that it is not stretching or changing it's dimensions very much when I fire form it. I am speculating it's because of the relative tightness of this chamber & headspace vs. the one on my Mauser .308 with 3000 rounds thru it. The cases that come out of it will only travel into the case gauge to the length of the neck before stopping. I just resize the necks and I'm good till the bolt starts to get hard to close. I was just interested to see if someone else had experience a similar situation. Several other posters mentioned that they had cases that would drop into a case gauge without being sized. They also thought it had to do with the relative tightness of the chamber & headspace.