Weekly Gear Update – Expander Mandrel Dies

Incremental improvements to reloading techniques and tools help to save time and gain consistency in precision hand loaded ammunition. One of the recent additions to the 6.5 Guys’ reloading benches is the use of Sinclair Generation II Expander Mandrel Dies. The mandrel die helps to minimize overworking the brass in the neck during the case resizing operation and provides a very uniform neck tension prior to bullet seating. In this gear update episode Steve and Ed briefly discuss this new piece of reloading gear. For more information go to the Sinclair website: http://www.sinclairintl.com/reloading-equipment/case-preparation/neck-turning/turning-expander-mandrels/sinclair-generation-ii-expander-dies-prod38807.aspx

Different sizes of mandrels are available (.001″ and .002 under caliber size). These allow you to control neck tension in addition to the other benefits you will experience using a mandrel. Most expander balls are .001″ under caliber size so if you decide to go with the .002 under mandrel you may need to drop your busing size down by .001″.


Latest Comments
  1. Mike McGee

    Have you guys got some setup tips (a video would be great) on using the Sinclair Expander Mandrel. The first time i used it I crushed the brass. Since there are no instructions on setup I have been using trial and error trying to figure out how far into the neck the mandrel should penetrate. This is difficult to gauge but I finally dipped the mandrel into some graphite and then set the die height by running an empty case fully up in the press. I then slowly turn down the die body until the top of the mandrel (the flat top) is approximately even with another empty case that I hold upside down on top of the die body,and watching the flat end of the mandrel until it is even with the junction of the case neck and shoulder. This seems to work ok but judging from the marking of the graphite on the business end of the mandrel it only penetrates the neck a couple of millimeters.

    • 65guys

      We do what you do, but we color the mandrel with a sharpie. We set the mandrel so the top of the neck makes it up 2/3 of the way up the mandrel. That way the entire neck is being sized but you are nowhere near crushing the case.

  2. Gary Shaw

    Hi Guys, I adopted the Redding/Sinclair bushing/mandrel method after watching the video.

    On my 6.5 CM sizing I’m getting pretty consistent neck OD’s of .289(+/- .0005″) using a .286″ bushing and neck sizing mandrel as Ed suggested. With the final rounds at .291″, this gives about .002″ neck tension- +/- the .0005″ variation I get, maybe due to spring back?

    My question is, assuming this variation in neck tension is ok, are there further things I can do to reduce SD and ES? I struggle to get SD below 12-15 and SD below 18-25. I do not neck turn and I don’t brush the inside of the necks to remove carbon build-up. Should I do this? Other thoughts? – Thanks!

    • 65guys

      Did you try to work up to your load? It could be that you are shooting outside of an accuracy node. How are you dispensing your powder?

      • Gary Shaw

        I just went to the new RCBS Chargemaster Lite. I load to 0.1 gr below each charge on the Chargemaster then drop in a few kernels to get the final 0.1 gr reading. The Chargemaster Lite frequently overcharges by 0.1 gr without showing the over charge on the display.

        In my note above, I meant to say that I was struggling to get “… SD below 12-15 and “ES” below 18-25.” Also, my lowest SD/ES loads do not occur in a ‘Satterlee’ velocity accuracy node.

        An often frustrating and demanding ‘journey’

  3. njaimo

    Hi There — Absolutely great work you guys do sharing all this !
    I am sure I am missing some understanding, but let me tell you what I do.
    I have been using Redding’s bushing dies, without expander balls at all. I am not sure I understand why I need to expand the neck again after cinching it down with the bushing die ? If I am careful with my powder measurement I easily get sub 10 fps SD. If I am using a -0.002 bushing, why would I need to expand with a say, -0,002 expander after that ? If the expander actually opens up the neck, then the object of using the bushing die to achieve neck tension seems mute ?

    What am I missing here ?
    Cheers from an old Wazzu alum…

    • 65guys

      Glen Zediker covers this in his book Handloading for competition. Unless you turn necks, even the best brass with have variations in neck thickness. If you don’t use a mandrel or expander, your bullet becomes the expander. Therefore, it’s better to resize the necks just an extra bit and let the expander/mandrel set the final neck tension.

      • njaimo

        …learned something new, Thanks !

  4. NMLR

    Do you guys turn necks ? Does Scott ?

    • 65guys


      We do not turn necks. Same goes for Scott. Some time back Scott played around with neck turning but he didn’t consider it worth the effort. He got better results setting neck tension with a mandrel.

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