Headspace is the measurement from the bolt or breech face to a point on the chamber. To understand the importance of headspace, we first need to understand what happened to the case when it’s fired. After the primer ignites the powder an immense amount of pressure is generated that expands the brass to create a seal against the chamber and to propel the bullet down the bore. While the walls of the case are forced against the chamber the base of the case will also expand and press against the bolt to breach the face.
In this article, we are going to talk about how we’re going to size properly size a case to set the headspace to fit in our chamber and match through your brass to your chamber. So let’s explore it…….
The first step of the process is to use to set shoulder bump or headspace. We all want to free-flowing bolt movement instead of block movement. On a regular 700 Remington rifle, you can remove the whole firing pin assembly and just install the bolt in the rifle. When the brass has done its stretching thing and when we go to the wreath to put this back in the chamber what we see is: we’ve got a pretty firm bolt closure but we don’t want that. We want to make sure our sizing process moves that shoulder back enough that. We don’t get that tight closed but we want to control that so we don’t oversize it. If we oversize our brass we end up with ammunition that resembles factory ammunition which is one size fits all chambers and it’s oversized and it’s not a custom fit with our brass to our chamber in relation to each other.
Now, we’re going to do is set of reading competition shell holders. Here we are going to start with the number 10. The number 10 is the shell holder that does the least amount of work to your brass which means these shell holders are all the same dimension across the side. But on the floor of the shell holder, they’re in different heights which means as we step this up it will put the piece of brass farther into the die doing more work. so we’re going to start with the one that does the least amount of work the number 10 and we’re going to put that into our Hand reloading press. However, we don’t need guerrilla strength going on but we need to have enough tension on that cam over that even when we put a piece of brass in here we will remain a zero clearance between our shoulders and die at all times. If you don’t do that you’re not going to get consistent work if one stops a couple thousand before the next one goes all the way so you want a consistent cam over for your shell holder. We know our piece of brass is tight in the chamber and we’re just going to be doing the body size. Here we sized the size of the case and the shoulder and we put a little case lube on running it through with the number 10 shell holder. Clean off the lube and try it for a test fit in your chamber. If it’s better then it’s okay but if you still feel the tension then we jump over the next process.
However, going to take our number 10 out and move one step up to the number eight which is going to essentially move my brass up into the die. After setting the number eight, we’re getting better each time. Now, we take out our number eight and move to my number six, and size it. Well, that’s just about zero and we can barely feel that we are just touching that case. Our next movement is going to our number four shell holder which is going to push that shoulder back essentially and that’s going to give us the 2000s headspace clearance that we’re after. Let’s see what we got here. There is no tension both absolutely no tension on that and there’s no headspace between the two.