question… newbie here. I have a Hornady match grade die set for 300PRC , which i believe is a full length bushing sizing die. Question is, it comes with an expander mandrel or just a recapping pin retainer if you don’t want to use an expander, if I’m using a bushing, do I also use the expander mandrel that came with the kit or is it just a one or the other deal? Also, I ordered a size .334 bushing, any input on what size bushings you guys use?
- Thread starter Nitro727
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The thickness of the neck on your brass will determine what bushing you need to use to achieve desired neck tension. A piece of brass with a bullet loaded in it. Measure the total diameter of the neck. Or do bullet diameter + neck thickness of brass for both sides. Then subtract .003” of whatever you choose for tension while accounting for spring back
The expander can be used with the die. Or removed and allows you to set neck tension with a mandrel die.
Lots of guys will size .003” under with a bushing/expander removed. Then run a mandrel .001” under the total diameter. Which will result in usually around .0015” neck tension
Which can obviously be adjusted with the mandrel and bushing to achieve whatever tension you want. While minimizing working the brass
The expander can be used with the die. Or removed and allows you to set neck tension with a mandrel die.
Lots of guys will size .003” under with a bushing/expander removed. Then run a mandrel .001” under the total diameter. Which will result in usually around .0015” neck tension
Which can obviously be adjusted with the mandrel and bushing to achieve whatever tension you want. While minimizing working the brass
For 300-PRC, I use a Redding FL Type-S Bushing die ... with the decapping and sizing pin removed. I use a .335 bushing from Short Action Customs, and finish off with a .3055 mandrel. That setup works great for me. When I get a sizing die, the first thing I do is yank out the decapping/mandrel pin.
Actually, that "expander mandrel" as you're referring to it is actually an expander "button". While it can function just fine for most people, those who wish to have good neck concentricity will not use the button as it tends to induce too much runout. Using a separate Expander Mandrel works a lot better in keeping neck runout to a minimum. And doing so adds an additional step you your process. . . . so, pick your poison.
Here's what the an expander mandrel set looks like:
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