How to improve the function of expander mandrels and gage pins

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[@techdiamondtools9594]

Hi, John, Thanks for featuring our diamond pastes in your video! We were extremely excited to learn about it from a customer's review and to watch it. Please, drop us a line if there are other projects we can help with. Thanks again!

[@FClassJohn]

Thank you and I appreciate that.

[@FOPRange]

Thanks John. I learned some great tips every time I watch

[@conservativesniperhunter7439]

Thanks F-Class John , that’s a great tip .

[@markbreidenbaugh6033]

Love a good polish. I had a Lee bullet sizer for 9mm and it was about a though and a half under sized and was rough taking the powder coat of the bullets I was sizing so I reamed it out with a dowel rod with some sandpaper then polished it to a mirror and she runs smooth as butter and does not remove any powder coat.

[@MMBRM]

Thanks for the video John. In my case I was able to isolate the deposit problem to the annealing process. I added an annealer(the only change) without wet tumbling and noticed a gritty feeling with both my sizing die and mandrels. Then I noticed that a brass colored residue was collecting on my mandrels when it never had before. I had to actually use a green scotchbrite pad to get it off. As soon as I started wet tumbling with SS pins after annealing this went away completely. My guess is that the annealing process is leaving an oxide layer which is then mechanically removed and deposited onto the mandrel/die. Wet tumbling does mean you'll need to lube the necks before bullet seating for precise consistent results. Obviously polishing will still help in any case as it means less friction.

[@o2wow]

Great advice, i've been polishing pistol caliber expansion dies for the same reason.

[@SimpleLife1971]

HA, I've been doing that for over 20 years, not bragging, but it's great to see I get something right on occasion! My diamond compound is actually in glass tubs with metal screw on covers! I have mandrels in both flavors, Carbide, and one's I made from HHS drill blanks..

[@FClassJohn]

Great minds think alike!

[@aeroderek]

who woulda thought that watching a guy polish his shaft would be so informative🤣

[@stefanejonsson2044]

Not to mention the tip... 🤭

[@luckyshotammunitiongunsllc2369]

Don't forget the tip

[@davidsalsedo]

Haha

[@davidsalsedo]

Fantastic John! Thank you

[@FClassJohn]

Glad it helped.

[@JimWooddell]

Hey John! Good idea! As a health risk, any time you use super fine polishes, such as 8000 grit diamond, gloves should be worn. 1 to two micron diamond will go through skin pores and accumulate in the body. Spent a lot of time making thin sections and this was always a safety requirement when polishing.

[@FClassJohn]

Thank you and that’s good to know. It figures the one time I don’t have gloves on is one of the times I need to. 🤗

[@JimWooddell]

@@FClassJohn If you can find some shipping paper with the shinny coating on one side, this stuff is great for holding the diamond (on the non shinny side). I use a little gun oil and mix the diamond and it keeps it lasting a long time. The diamond will last a very long time. I use 14,000 mesh (1 micron) diamond powder and gun oil. Looks like a mirror when done!

[@CallMeUbba]

@@FClassJohn exactly what I was thinking. “Good thing John always wears gloves. Oh wait!”

[@ericrumpel3105]

I use the diamond compound on new barrels for years now - great stuff, .....also use cotton polishing wheel on bench grinder for mandrel's aswell.....

[@Kycirion]

Are you lapping the bore with diamond paste? How fine and how many strokes does it take for a good lap?

[@Sw00per_actual]

"mostly the tip but some of the shaft"... That's what I told her when doing a demo of this technique. ;)

[@linklesstennessee2078]

Good information

[@amirdzaferovic3489]

good job

[@nt_wicked_bunch2717]

That’s funny you released this video, I just did my century 21 expanders last night. “Mother’s Mag Polish” from Walmart works well for me. It takes a bit longer but is very cheap and easy to get ahold of.

[@FClassJohn]

That's great. I'm sure there's a number of polishes that could work and that looks like a pretty good one for the price.

[@davecundiff3663]

I use Mother's Mag polish on my car plastic headlights. Does a great job.

[@jaybigboy34]

Thanks for the tip! We are ready for an update on the 6.5 prc necked up to 7mm!

[@FClassJohn]

It's coming soon. I have several decent sized matches this month and will putting it to the test again.

[@bobsmyself]

It's the creme de la diamond for collet pins, though in a rush I've good success spinning in grey scotch brite.

[@patrickcolahan7499]

For my .308 Lapua Win brass I use a 0.336" Neck Nitride Bushing. This produces a 0.337" Neck OD, I then use a 0.3075" Minus gage pin to expand resulting in a 0.338" Neck OD. One of the critical things that I have learned is that on unturned necks, you need to hold (dwell) the case in the die and expander at least 15 seconds (I dwell for 18 sec) to eliminate spring back. This is for a neck wall thickness of between 0.014" to 0.015". Some are turning necks to below 0.010" and with some testing, I have found that dwell time can be reduced to as little as 10 seconds. This is all assuming that you anneal every time before sizing to ensure that the metal is consistent. I recently began turning my necks and would like to go to a smaller bushing size, but cannot find any available right now. But will go to a 0.335" or 0.334", which is to be determined with some testing. Thanks for sharing John, a great way to polish the gage pins after tapering.

[@snajjpern]

Have you tried annealing the case necks, helps to minimize springback and you will have more consistant resizing. Atleast it works for me. I have about 3 sec dwell.

[@patrickcolahan7499]

@@snajjpern I anneal every firing. The thing is that when you size the brass you put back the hardness that was removed by the annealing. So each step, (Full Body, Neck, Expander) all are working to harden the metal during your sizing processes. Annealing therefore, is more of a resetting rather than a softening. The makers of the Annealing Made Perfect machine did a great review of this on YT. I have found in my studies that the thicker the neck wall the longer you need to dwell. For Lapua Win brass at 0.015" neck wall I need at least 12 seconds, 15 seconds allows for variations in metals. I do 18 seconds just to be sure. Using this method, I have a consistency of 4 tenths in Neck OD over 100 shells.

[@TubeDobs]

I'm using Autosol for years, work great.

[@FClassJohn]

Yep I see that working well too..

[@magic4221]

Being a machinist , the trick i use after the 8000 grit is to use Ultra Brite toothpaste as a final polish. Amazing results.

[@FClassJohn]

I'll have to try that. Thank you

[@magic4221]

@@FClassJohn You are very welcome. You have shown me so much it's only fair.

[@devurandom2019]

Great video John. Are you still using your expander mandrel gauge pins with the Porter Precision dies? You have an older video where you used 21st Century expander mandrel dies for a while. Any thoughts on the K&M neck tension expander mandrels and dies?

[@JR-lg7fd]

ahh crap. I just checked for F Class John's playlists, but he doesnt have any yet.

[@johnplummer1619]

I use 2000 and 3000 grit auto body sandpaper

[@christiankovach8776]

Where do you get your gauge pins and dies to hold? I can’t find it. Thanks

[@mickroberts5166]

Hi John, how about a video testing the actual target results between expander mandrel neck prep and a Lee collet die that so many people use with apparently equal if not better results to expander mandrels?

[@FClassJohn]

I appreciate the question but it's not a test I want to do. For my purposes the first thing is that they don't make it in any cartridge I shoot and secondly it's only a neck sizer and want to full length size every time. I know people like them and that's totally fine and there's always more than one way to slice an apple. As long as the apple gets cut the way you want then that's great.

[@mickroberts5166]

@@FClassJohn It is still FLS, just in two steps, body only and neck separately. You may be surprised by the difference in runout and accuracy. Just saying.

[@georgedeedsnotwords2162]

Have you seen the 3 micron diamond sand paper ? Or 5 micron ? Leaves a mirror finish .

[@FClassJohn]

No but that sounds intriguing. For me I like using the polish because I feel like it takes the shape of whatever you’re polishing a little better than a rigid surface like sandpaper where I might create an inadvertent groove. I know some people are really good with sandpaper but to be honest I’m not one of them.

[@Pathfinder76]

Been doing this for years with Iosso.

[@FClassJohn]

I can see that working well too.

[@CoyoteRegulator]

John why dont you use the Century 21 Nitride mandrels? You don't need to polish those right?

[@FClassJohn]

I prefer using carbide over coated plus I prefer gage pins over expander mandrels. Just a preference thing.

[@snajjpern]

So do you buy bigger mandrels since you are removing material? Its not much but I guess you hve messured before and after polish?

[@FClassJohn]

Yeah it’s not enough to make a difference in my experience.

[@terrellstandefer6646]

I think you're trying trying to see how many jokes or dirty comments you can get from this video, hahaha!

[@mckimmym]

How far under your mandrel diameter do you size the necks before expanding?

[@FClassJohn]

In my case I use a .311 size on the neck and then expand up with a .281 gage pin. I've played around with other combos that is what's working the best for me now.

[@1clnsdime1]

I leave .004 with the die that way the mandrel has .002 to expand to leave me with .002 press fit or neck tension.

[@mckimmym]

@@FClassJohn ok, so the mandrels not having to do a lot of work, assuming your neck thickness is about .015. Surprising that the brass is rubbing off even with those dimensions. Amazing what you find out when you get into the nitty gritty details.

[@whateman12408]

How much does this change the diameter

[@FClassJohn]

I didn't find it made a measurable difference (at least measuring to .001. I suppose if you ground on it long enough you could.

[@hughtanner208]

please remind what gauges you are using

[@FClassJohn]

I have everything from .279 up to .2845 but use a .281 right now.

[@hughtanner208]

@@FClassJohn sorry and I was not clear. The manufacturer.

[@davenimetz3129]

@@hughtanner208 21st century, unless he has changed in the last year or so. That is what I run and they work great

[@Rico11b]

Hehe...hehehe....hehehehehe.... He said... shaft. lol. It would work better on a piece of leather. Just do 3 spots on the piece of leather and you can keep reusing it.

[@jeffhicks8428]

Too many potential jokes about tips, shafts, rubbing it off. Keeping it serious though, while these are readily and easily available and for cheap, it's still expensive stuff if you use it a lot. Using a paper towel is far from ideal. That amount that you used there could go idk 100x further if you used something proper to put it on rather than a paper towel. Thats my tip of the day.