If I am going to use the sinclair oversized expander mandrel after running through a full length sizing die, should I change my bushing to a slightly smaller size? The mandrel should create 0.263" id for use with .264 bullets? I am currently using a .289 bushing on the hornady 6.5CM brass.
Mandrel die question
- Thread starter SleepDoc
- Start date
Sinclair sells two mandrels in each bore size. You want the "T" (turning) mandrel, not the expander mandrel.
I use the expander mandrel on the inside of the case neck. The turning mandrel is the one I use next, when I have to turn the case. Turning is only done once, or after many loadings, if there is neck interference (fired case will not let a bullet fall through). The turning mandrels have two calibers, one on each end of the mandrel, so they go in your neck turning tool easily, and the second caliber extension is used to attach the hand drill. The expander mandrel goes in the Sinclair die body for expanding the neck. Also, if you use the Lee collet/mandrel neck sizing die, get the oversize mandrel, which will more closely match the Sinclair expander mandrel, should you need to neck turn. Using the Lee collet/mandrel neck die causes less overworking of the brass than any other sizing method I know.
I dont believe the OP is using the mandrel as a prep for turning, but to avoid having to run an expander ball in the sizing die. I suggested the T mandrel, because theyre .001 undersized from the expander if I recall correctly.
I need to ask, what are your projected gains by running your brass through a mandrel, because I am lost on this trend?
Yes, I am not planning on neck turning. The expander mandrel is 0.001 under (.263) and the turning mandrel is .002 under (.262).
I process brass the same way, size the outside of the case with a FL die, then use expander mandrel as a second step to expand the neck to final tension. I'm doing it with a custom honed FL Forster die but a bushing die would work too. I use the turning mandrel since I want 0.002 neck tension. I also got the carbide version of the turning mandrel since I didn't want to have to lube the inside of the neck. Spendy but it works great.
As far as choosing a bushing size (or what size to hone the neck of a Forster die to) I would base it off outside neck OD measurements. Start with a loaded round neck OD, subtract 0.002 and that's your finished size target after the expander die. You want the size after the FL die and prior to mandrel to be maybe 0.001 smaller, so a bushing that's 0.003-0.004 smaller than loaded neck OD is probably about right, depending on springback. One of those things you'll have to test/measure.
Milo, the advantages IMO are that you get less runout by using an expander mandrel separately vs using an expander ball in the sizing die. It also evens out the inside of the neck for those of us who don't neck turn and it helps out if you've got case mouth dents from field shooting conditions. From my perspective on a Dillon press it adds no extra work since the expander mandrel just takes up one of the empty slots in the toolhead.
As far as choosing a bushing size (or what size to hone the neck of a Forster die to) I would base it off outside neck OD measurements. Start with a loaded round neck OD, subtract 0.002 and that's your finished size target after the expander die. You want the size after the FL die and prior to mandrel to be maybe 0.001 smaller, so a bushing that's 0.003-0.004 smaller than loaded neck OD is probably about right, depending on springback. One of those things you'll have to test/measure.
Milo, the advantages IMO are that you get less runout by using an expander mandrel separately vs using an expander ball in the sizing die. It also evens out the inside of the neck for those of us who don't neck turn and it helps out if you've got case mouth dents from field shooting conditions. From my perspective on a Dillon press it adds no extra work since the expander mandrel just takes up one of the empty slots in the toolhead.
I run bushing dies, no expander ball, have mandrels, 1 carbide for 6mm, I rely on the bushing for tension. I hear a lot of the expander evens out or pushes inconsistencies to the outside, has anyone verified this with a dial indicator? I can see if brass was glowing red, it'd be possible.
Biggest inconsistencies I run into are having stepped on the brass in a stage at a match. Mandrel helps a lot in pushing those back out, lol.
I run 21st Centruy TiN mandrels to set .002 neck tension on a XL650. I do this because I use the Dillon trim dies to bump shoulder back and trim to length but it doesn't set neck tension so it then goes into the expander mandrel. I process large batches of 5.56, 308, 300blk and 6.5cm this way with very little runout.
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