case seperation

[kyhareraiser]

 i had a case to seperate as i was shooting my 15" 308 win t/c.. i reload and i was using 41 grain of h4895,,,165 grain nosler BT ,,winchester ,standard rifle primers   WLR.  i double check my powder charge weight b4 puttig the bullet in.  j a fluke i figured so i shot 3 more ,they dd'nt sepeate ,however there was a marking arround the cases. what do yo reckon' could have gone wrong.. about the only thing i did diffrent was ,i went from cci primers to the wincester. the primers show no signs of pressure .

[trotterlg]

Probably more from how many times they were reloaded than how hot the load is.  In the Contenders and other break open rifles, the action allows the case to streach more than a bolt gun does because the barrel springs forward some when fired.  You can bend a little hook in a paper clip and stick it down the neck of a fired cartridge, drag it up the wall down by the base, if you feel a little catch down there, it is the case thinning from the inside from streaching, and you are getting close to a seperation.  Larry

[gunnut69]

It may be something as simple as your sizer and chamber being at opposite ends of their respective tolerance ranges. A maximum chamber and a minimum sizer will over work the brass and even though every thing is in spec there will be failures.. To work brass less try partial sizing the fired cases. Run a fired case into the sizer until the contender just closes and then a tiny bit more on the sizer(contenders don't like long cases). This will give cases the least amount of sizing possible and work the brass the very least.. I've never checked contender cases but if they flex then one would expect the caseheads to be badly out of line with the case centerline.. Has anyone ever checked?

[Val]

I don't know how long you've had that rifle or how much you've shot it but, it could be an excessive head space issue. Consider getting the head space checked.

[Mosinman]

Case separation has more to do with repeated use than load quantities.  Every time a case is resized or run through the die, it stretches and there is a thinning of the wall of the case.  Sometimes the dies will leave a "separation line" around them, sometimes not, but they are still being thinned as they are used and resized.

My reloadable mosin brass is good for about 3 cycles before I have to do case trimming, etc. but should be checked after every firing for length.  If the press is leaving a "thinning ring" around the case, they need to be examined to see if there is simply a mark around the case, or a "dimple" where the brass is separating.

Remember that a bullet is nothing more than a controlled explosion inside a mechanical chamber designed to push the results out the barrel, and when it occurs in the wrong place, all kinds of bad stuff can happen.  Reloaders need to be aware of their "use count" for brass, and not assume that it is safe just because it's still shiny.  The bigger the caliber, the more violent the results of case failures, so keep your brain in while you reload calibers like .300 Win Mag, etc.   You can get into some powder loads that will take the top of your head off if you have a mechanical failure.

[gunnut69]

Rimmed and beltd cases such as the 7.65 Russian and 300 WinMag head space on a rim or belt but they have shoulders. When the round is fired brass stretches to fill the chamber. This stretching moves brass from just in front of the solid portion of the case, at the head or belt, and creates a thinned area there. If flexing action were the problem why do perfectly good bolt guns have identical problems. This is easily solved at the reloading bench. Just adjust the sizer to size no more than needed to allow the case to chamber. Since the case will now be headspacing on the shoulder and not the rim/belt the stretch will be nearly gone. All brass fails but usually with any sane load it is from metal fatigue. The brass at firing expands and seals the chamber, then springs backa tiny bit to allow extraction. Eventually the brass work hardens and cracks. Most often this ovvurs at the neck of the case and even this can be combatted by annealing the neck area..

[SHOOTALL]

Before reloading those or any cases that have been reloaded its easy to check . Get a piece of wire , bind one end so maybe 3/16 inch sticks out to the side and cut it so there is a point on it . Slide it in the case and go up and down inside to feel a groove forming . If you feel one trash the case . I had to do this with a 30-30 and 7BR cases