How much is it? Does a case expansion of 0.004 inches indicate a sloppy or oversize chamber, does 0.008 inches near the neck?? Just how much case expansion and case shortening would indicate a so called sloppy chamber?

Jimmy,

The answer to your question is not as simple as it appears on the surface. Standard chamber and cartridge specs are published by the Sporting Arms And Manufacturers Institute (SAAMI) in the United States. The drawings supplied by SAAMI each include dimensions for a “maximum cartridge†and a “minimum chamberâ€. All tolerances for the minimum chamber are in the “plus†direction, and as you might guess; all tolerances for the maximum cartridge are in the “minus†direction. This ensures that the cartridges ALWAYS fit in the chamber. The amount of clearance between a maximum cartridge and a minimum chamber is not exactly the same for all cartridges, but it is typically about .001†at the base of the case, .0015†at the shoulder and somewhere between .002†and .003†at the neck. This is a very nice fit. Using the 30-06 Springfield as an example the diameter tolerances for the chamber are +.002†and are -.008†for the cartridge. If you are unfortunate enough to have a combination at the limits of the allowed tolerances you have over .010†of clearance! And all of this is within SAAMI tolerance! If your chamber was cut poorly and is oversize then it can get pretty ugly fast. That’s why it is common practice for benchrest competitors to select the most uniform brand of brass available and then lay in a good supply. Then they have a chamber reamer ground based on the measured dimensions of their brass. Getting back to your question, based on the above numbers you could see a little over .010†expansion and still be in spec! Brass ALWAYS runs at the small end of spec. The chamber is up to the reamer and the person cutting the chamber. Sorry for being so long winded, I tend to run on about things that interest me!

It just so happens that I have a 30-06 that I am picking apart now! With WW brass, federal LR primers 57 grains of IMR4350 and bulk 165 grain corloc bullets the fired cases are shorter than the length I trimmed them to. I trimmed to 2.490, loaded them, shot them and the lenght miked out at 2.485. Then I checked width. An unfired store bought WW 165 grain power point loaded cartridge width measures .436 under the shoulder and .465 right above the base. The fired cases width measured .442 under the shoulder and .467 right above the base. My cases are expanding .006 and shrinking in lenght. I guess at below 0.10 expansion the chamber is in spec?

quote:

I guess at below 0.10 expansion the chamber is in spec

NO! 0.010 maybe. My chambers seem to run about .4671 or so. The brass I use goes ~.4665/.4668 when new. This is for 30-06 and 308 brass and in , 7-08, 25-06, ect their various forms.
A benchrest shooter likely will concider any more space in his chamber then needed to allow a cartridge to fit as excessive. A hunting rifle needes some space to allow easy chambering. A military rifle will have a larger chamber yet.

I Miss-typed! the expansion is 0.006 inches...so I guess in spec..what worries me is that the cases are shorter is this a problem?

quote:

Originally posted by Jimmy P Coaltrain:
I Miss-typed! the expansion is 0.006 inches...so I guess in spec..what worries me is that the cases are shorter is this a problem?

Nope! Full size your brass and you will likely find it is longer then it was before you 1st loaded it.
The sizeing process squeezes the walls back into spec and the displaced brass squirts up and lenghtens the cases. Normal occurance and nothing to worry about.

quote:

Originally posted by Jimmy P Coaltrain:
I Miss-typed! the expansion is 0.006 inches...so I guess in spec..what worries me is that the cases are shorter is this a problem?

The case getting shorter is normal. Few people bother to check it after firing so they never see this. When you resize the case gets longer again as Joe says.