Head space gauge

Reach

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New to reloading and was told by my friend i should get a head space gauge for the cases. Cant find them anywhere. I see them for others. I have a 7mm STW..TY...Pete.
 
Trying to figure out why your friend would suggest you need a headspace gauge to reload. In my opinion you don't need one.

You say you are new to reloading. I strongly suggest you buy a loading manual like Hornady or Nosler. These books have a chapter devoted to how to load ammo. There are many details that you must follow or you will have poor results or even endanger yourself.


When chambering a barrel there are usually two headspace gauges used. They are called go and no go. The idea is to get the depth of the chamber so that the go gauge fits but the no go doesn't fit. The difference in length between the two can vary but it is usually somewhere around .003" to .005".
I think your friend is perhaps thinking of the fit between the once fired brass and the chamber when you resize your brass?

You can tune the fit between the rifle's chamber and sized brass by regulating the depth of a full length sizing die. While an auto loader may require quite a bit of resizing, a bolt action can handle a tight fit. If you are a hunter you may want the brass to fit so that there is no resistance when you close the bolt. If you shoot targets you could fine tune the fit with a tiny bit of resistance when closing the bolt. Or you could even neck size and not do anything to the body. Eventually even neck sized brass must be partially full length sized or after several firings the bolt can be too difficult to close.

The way to partially full length size fired brass is to set up the full length die with a space between the shell holder and the end of the die. Size a fired piece of brass, wipe it off, then try closing the bolt on the case. Progressively lower the die until you get the fit you want. It is common to get to a point where the brass becomes more difficult to chamber. Eventually you will reach the setting that will allow you to close the bolt with minimal resistance or no resistance at all. It is up to you. If you insert a few feeler gauges into the space between the shell holder and the die you can duplicate space between the die and shell holder for the next sizing session. You could also tighten the setscrew on the die's tightening ring but in my experience the setscrew doesn't always keep the ring at the proper setting. Regardless of the method it is advisable to size one piece of brass and try it in the chamber. Then fine tune if necessary.

What you don't want to do is just screw the die down till it contacts the shell holder and size. You could be pushing the shoulder back too far which will over work the brass. During the sizing process some brass flows towards the neck increasing the case length. When this happens it will very slightly thin the area just in front of the web near the base. If over sizing is done for several firings the case could get dangerously thin in that area and eventually separate. There are signs that this is beginning to happen which is usually discussed in loading manuals. I KNOW about case head separation because I did it with my first rifle 30 yrs ago. ( I followed RCBS's instructions and adjusted the die to contact the shell holder).

Even partial full length sizing will cause some case lengthening. At some point you will have to trim the brass so it doesn't contact the end of the chamber and hinder bullet release which will spike pressures.

I hope this makes sense. There is much more to handloading. Read up, ask questions and if possible have a seasoned handloader at your range show you some techniques. Most of us had someone show us handloading techniques when we were just starting out.

Feel free to ask questions here. Many here are willing to help out a beginner.
 
AZshooter, he's asking about a case headspace guage, such as the RCBS Precision Mic to measure fired and full length sized cases' dimension from head to shoulder datum. Good thing to have for setting up a full length sizing die such that it sets fired case shoulders back only a couple thousandths.

You mention a bolt action can handle a tight fit of the loaded case in the chamber. I disagree. Tight fits that make the bolt bind a bit when they're closed hurts accuracy; especially in rifles whose bolt face ain't squared up with the chamber axis. There needs to be a tiny bit of clearance so the bolt will close to the same place with the same fit ant tension for each shot if accuracy is important.
 
Title said head space gauge.....

Bart,

As for firing rounds in a bolt action that are tight, I don't mean having to hammer the bolt closed but firm enough that it could prevent an auto loader from going into battery.

I understand what you are saying Bart. I have neck sized brass till it became a pain to close after several firings. I'd then bump the shoulder back for easier bolt closure but still a light firmness of resistance while closing the bolt. I never noticed a change in accuracy as the cases got tighter. It seems to me that a firm fitting case would be centered in chamber and cause the bolt to end up being square if there was slop in bolt. Never read any issues with neck sizing in Precision Shooting or on 6mmBR.com.
 
Title said head space gauge.....
But the OP's comment was: New to reloading and was told by my friend i should get a head space gauge for the cases. Which is why I suggested the Precision Mic.
It seems to me that a firm fitting case would be centered in chamber and cause the bolt to end up being square if there was slop in bolt.
A very popular belief, but another myth in the shooting sports reloading world. The front end of the case will be centered, but the back end won't be. It's the back end not being in the same place for each shot that causes accuracy problems.

Bottleneck cases headspacing on their shoulders center perfectly up front in the chamber where it counts when the firing pin drives their shoulder into the chamber shoulder perfectly centering it when the round fires. Doesn't matter how far the case moves from its resting point to shoulder contact with the chamber. Doesn't matter how much clearance there is around the case behind the shoulder either; centered is centered. And if the bolt's got an in-line plunger style ejector, the round's centered in the chamber up front as it gets pushed forward after the bolt's closed.

If the case headspace is .001" longer than chamber headspace for bottleneck cases headspacing on their shoulder and the bolt's closed on one, some binding happens. If the bolt face is out of square with the chamber axis, previously fired cases in that chamber will also have case heads out of square. If the case isn't indexed in the chamber the same way it was first fired, the high points of both bolt face and case head increase the binding effect and make the bolt harder to completely close. That off-center high-point contact place is where the force axis will be when the round fires. If there's any slop in the bolt fit to the boltway in the receiver, the front of the bolt won't end up at the same place causing the locking lugs to seat at different places against the receiver. All these force points cause accuracy problems as they're not repeatable from shot to shot. This is why the top high power match rifle competitors full length size their fired cases setting their shoulder back only a couple thousandths to ensure their rifle's bolt closes exactly the same for each shot. It makes the difference between a 1.0 and a 0.5 MOA rifle and ammo at 600 yards. The more the rifle's bolt face is out of square, the bigger the problem is. All of which it's important to have enough clearance lengthwise on the case to let the bolt close to exactly the same place for each shot. And if the locking lugs aren't lapped to full contact as the bolt closes to the same place, they'll have different contact areas with the receiver as the bolt head comes to rest at different points and that causes accuracy problems.

Even with severe out of square bolt faces, new cases (with reasonably square heads), excellent accuracy is possible. For example, good lots of commercial .308 Win. match ammo shooting under 2/3 MOA at 600 yards all day long in properly rebuilt M1 and M14 service rifles. Why? everything's pretty much repeatable from shot to shot.
Never read any issues with neck sizing in Precision Shooting or on 6mmBR.com.
Those competition rifles they discuss have their bolt faces squared up and that minimized the issue mentioned above. But top ranked service rifle shooters using M1 and M14 competition rifles know very well that when you load a round in their chamber, you don't bump the op rod handle "to make darned sure it's closed right" at all because doing so will reposition the bolt and op rod and if they both ain't in exactly the same place for each shot, accuracy goes down the drain. And no 'smith I know of (military or civilian) ever squared up those service rifle bolt faces which is why they never shot resized cases fired in them very accurate; case heads were permanently way out of square.
 
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