expanding button or mandrel

SJB358

Ballistician
Dec 24, 2006
31,398
757
I have been using the Sinclair Expander Mandrels for a few years now. Dr. Mike turned me on to them. I buy the expander mandrels .002 under size and use the pin gauges to check for how much neck tension I am getting. Typically I have about .003 neck tension with good brass that isn't work hardened. Even using the Redding Bushing Dies I will use the expander mandrels for my Mashburn and 338 Win Mag. I have no idea what is best, but I tried neck turning and prefer not to do it. I have to inside neck ream my 7mm Mashburn Super brass after the first or second firing, in order to get rid of the donut that comes out from forming, but after that, I just shoot the stuff.

For me, going to RWS, Lapua, Alpha and similar has been a big money saver for me. Most of it is straight and concentric, with very little inconsistency right outta the box and if I am not firewalling my stuff it would blow your mind how many loads I get out of a piece of brass.

While being more expensive up front, it lasts longer, less fiddling to make it perfect and uses less components since I am not having to burn through as many components before finding great loads...

Great topic.
 

DrMike

Ballistician
Nov 8, 2006
35,465
2,246
Yup, I like the Expander Mandrels a lot. Scotty gave an excellent summation of their use and shout out for quality brass saving a lot of time and effort.
 

gerry

Ammo Smith
Mar 1, 2007
6,113
11
Very interesting information, I'll be rethinking how I do things from now on and can see adding some of the Sinclair mandrels in the future.
 

jimbires

Handloader
Aug 16, 2011
2,505
476
replies #11 - 13 say these will work in the sinclair die . the same 3/8 diameter shank .
 

jimbires

Handloader
Aug 16, 2011
2,505
476
TackDriver284":c4pm6qcu said:
Thanks Jim. I hadn't read that comment there before I saw yours. :grin:



no problem Mark , I see you got your answer right from the guy . you've got to weed through , but there is some good info on that forum .

I don't read there much any more , for awhile it was like nonstop fund raising for the forum .
 

RAD57

Beginner
Mar 7, 2019
25
19
I use expander mandrels and Forster FL dies honed to the diameter that I want. My honed FL Forsters are kissed (.0005-.001") by the expander button while the neck is still supported by the die. Using the Forster dies this way provides me with the lowest runout in most cases. I've found that with very thin brass as found in the 22 Hornet and 38-55 that using a mandrel can overexpand just one side of the brass, especially when you only can slightly neck turn to clean up about 50% of the case neck.
 
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