So, before you start making decisions, it’s important to know what you’re doing and what the goal is. And how we got there. I apologize if this is stuff you already know.
Let’s take virgin brass. It’s going to be smaller than your chamber. You’re going to prime/powder/seat (run a mandrel if you want, trim and such). Then you’re going to shoot it for the first time.
Now, you’re left with an empty case that is carbon fouled inside, has a spent primer, and has expanded closer to the actual size of your chamber (just depends on chamber, pressure, case hardness etc as to how close).
Now, the whole point of sizing is to do the minimal amount of down sizing as possible to get the desired fit in your chamber.
At a minimum you need the case to chamber easy as well as on the next firing have enough clearance to expand so the action’s primary extraction has no issues getting the case free for extraction.
I’m going to skip depriming, annealing, cleaning, etc. As each of those can be a separate topic.
So, now we have a case that has been prepped however you feel as far as the above things. It has no primer.
You will use your choice of lube (understand more/less lube has an effect on sizing). You’ll want the lube applied as consistent as possible across the casings.
So, now we have three part of the case we need to size (can be done with one, two, or three steps).
1: Body: this needs to be minimally sized down enough to chamber, fire, and expand….but not expand enough to get stuck. This is controlled by the body size in your die which was created using a sizing reamer (can Google those. Similar to a chamber reamer, just smaller in some dimensions).
Unless you spec a custom sizing reamer, you won’t have control of this. The die is what it is.
2: shoulder. You need to basically make the case length from base to shoulder short enough to fit in the chamber easily, and extract easily. However, you don’t want to make it too short. Otherwise it will stretch the body too much when fired which will make the body/head weaker. Eventually you will get case head separations.
I advice *NOT* to just push shoulders back a generic .002”. I suggest to use one of the several methods to check the fitment of your brass in the chamber (I personally use the wheeler method). Then decide what kind of fitment you want (I prefer the bolt to barely fall free with gravity). Then measure and see what the setback is. I’ve seen anywhere from barely .001 to .003.
3: Neck. So, the two above are basically done the same in a bushing or non bushing die.
The neck is where you choose which kind of die you want. There’s many thoughts on this. Sizing part of neck with regular bushing die, the whole neck with non bushing, or even the whole neck with some bushing dies that have a shoulder built into the bushing. I won’t go into it, as that’s also an entirely other topic.
You also have to decide how you want to set the final neck inside diameter/interference fit (commonly and incorrectly called neck tension).
- non bushing die with expander ball
- non bushing die without expander + mandrel after
- bushing die with expander ball
- bushing die without expander ball
- bushing die without expander + mandrel after
And then there are some sizing dies that have a mandrel inside instead of an expander ball.
If you turn necks and they don’t get beat up, you can use a honed custom non bushing die or a bushing die with the desired bushing. I typically don’t advice this on non turned brass.
Then the conversation goes into what size bushings and mandrels. But that’s also a whole other topic and it’s fluid. Change the bushing size and you’ll need to change the mandrel. Don’t anneal or change the spring back and/or hardness of brass, will need to chang other things.
Anyway, that’s the “what, why, and how” of sizing brass.
Once you understand this, then picking your equipment is much easier and just a matter of research, learning, and testing what you prefer or works best for you.
