Explain Headspace Please

[butterman]

Could someone explain headspace, Do I Understand it to be the room that the cartridge has to slop around in your chamber , and when you fire the firing pin might move your case foreward till it touches the shoulder ,or belt on a magnum .   If this is true then if you set your reloading dies up to just touch the shoulder ,with candle smoke , then is there no headspace??  So when you reload for semi-auto rifles like say the Rem. 742 in 30-06, you have to shrink the brass back to factory size ,So do you not get vary many reloadings with the brass before it stretches to much and the cartridge breaks into, so is it worth while to reload for this gun ??

[quickdtoo]

Maybe these will help.

Tim

http://www.recguns.com/Sources/VIIF1.html

http://www.fulton-armory.com/headspace.htm

http://www.rifleshootermag.com/gunsmithing/headspace_0612/

http://www.surplusrifle.com/shooting/headspace/index.asp

[Catfish]

Head space is measured differently on rimmed case than on rimless cases. With rimmed cases you head space on the rim of the case. With rimless case like your 06 you head space off the frount of the shoulder. The reason you need to set the shoulder back with your 742 Rem is because in semi auto`s your case will get more strech than in a bolt action where the action stays closed throughout the whole fireing, where your action is starting to open while the bullet is still in the barrel.

[Questor]

The reason for full-length sizing cartridges for an auto is for reliable feeding. There are three separate issues related to your question:

1) If the headspace is excessive in your gun, then case stretch can be excessive and that can lead to "case head separations" in which the brass fails during firing and hot gasses create a dangerous condition to you. This possibility is one reason we wear shooting glasses. For a 30-06 headspace is just the metal-to-metal distance between the bolt face and the shoulder in the chamber. If the distance is out of spec by being too long, the case will stretch during firing.  Related to this is case length. It is important that the length of each case be within acceptable tolerances.  If you are not getting case head separations, and the cases are not increasing in length considerably after each firing, then headspace problems are not an issue in your gun.  In any case, look up these topics in a good reloading manual to see what the trouble signs look like so you can prevent problems.

2) Reliable feeding in a bolt action or single shot is a more direct process than the feeding in an auto. In an auto the cartridge wobbles as it's being pushed into the chamber. For top reliability full-length sizing is recommended. Just neck-sizing may work fine in your gun. There's only one way to find out, and that is to conduct a reliability test for neck-sized cartridges.

3) Reloading for a rifle is only economical if you shoot a lot. Unless of course, you've already got reloading equipment. In that case, just buying a set of dies and a shellholder is all the new equipment you need. It'll pay for itelf within a few boxes of ammo, even if you only get three or four reloadings out of each case.

[butterman]

For case stretching some people said take a stiff wire and bend it at the end , then stick it in the case and   "  Feel  "  for a grove on the side of the case toward the bottom ,  I have tryed this and could never  FEEL  anything , is it supose to be  " odvious "  or am I just not getting stretch??

[Questor]

You're probably not getting stretch. The bent paperclip test usually goes hand in hand with an obvious lighter ring just above the case head.

[PaulS]

Headspace is the dimmension of the chamber between the bolt and the point in the chambering that holds the case from going any further forward.
In a chambering for a rimmed cartridge it is the distance from the back of the breach or face of the bolt to the step in the chamber that the cartridge rim fits.
In a chambering for a rimless cartridge it is the distance from the rear of the breach or face of the bolt and the median of the shoulder of the chamber.
In a chambering for a belted case it can be one of two measurments. The first one fits all but the original H & H magnums. Itis identical to the rimless chambering headspace because all modern belted magnums headspace on the shoulder and not the belt.
The second is for the H & H magnums and is the dimension from the rear of the breach or the face of the bolt and the step in the chamber that supports the belt.
There is always some tollerance in the dimension and that is why once fired brass fits the chamber better. Neck-sizing eliminates the stretching that is caused when the case is fired and fills the chamber. In severe cases this stretching will sause the case head and body to pull apart when the case expands to fit the walls after the firing pin drives it forward and the pressure then pushes the back of the case back to the bolt or rear of the breach. Case head separation can be reduced even in long chambers by firing a fire-forming charge the first time. Following the first fire-forming, neck sizing the case will eliminate shortening the case dimensions and the subsequent stretching upon firing. Case head separation is thereby prevented. As long as pressures are maintained within the yield strength of the brass and the chamber there is no reason that the cases should grow beyond the limits of the chamber and need any full-length sizing. For the life of the cartridges trimming and neck sizing are all that will be needed in the way of making them fit the chamber and trimming will be virtually non-existant.

[iiranger]

Could someone explain headspace, Do I Understand it to be the room that the cartridge has to slop around in your chamber , and when you fire the firing pin might move your case foreward till it touches the shoulder ,or belt on a magnum .   If this is true then if you set your reloading dies up to just touch the shoulder ,with candle smoke , then is there no headspace??  So when you reload for semi-auto rifles like say the Rem. 742 in 30-06, you have to shrink the brass back to factory size ,So do you not get vary many reloadings with the brass before it stretches to much and the cartridge breaks into, so is it worth while to reload for this gun ??

I had to do this for some administrators. they didn't think I could. i did. they hated me more...

#1). guns go bang? Right?
#2). Guns go bang when the firing pin strikes the primer? Right?
#3). The properties that support the primer against the blow are "headspace."
     the rest is details. Obviously, the rimmed cartridge be it .30/30 or .38 Special stop on the rim. Belted cartridges originally stopped on the belt. The real freaks, .45 ACP and .30 Carbine, among others, stop on the mouth of the case. And the shouldered rimless stop on the shoulder...
On the down side, if the distance is much too large, the firing pin cannot reach the primer. NO BANG!  In between, DANGER, if the firing pin sets the round off and the neck grips the chamber, but the base has to stretch back too far and comes apart, then you have gases loose in the gun at 1 or 2 or more times the temperature of a cutting torch. If you are lucky, you are dead. If not, you wear dark glasses while they rebuild your face.luck