Forming 6mm TCU cases

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Forming 6mm TCU cases

Post by Rathie » 20 May 2020, 11:36 am

Gday All,

I have a TikkaM55 at Swanns having a 6mm TCU chambered barrel installed.

A 3 piece Redding Die set has been ordered and should be here within 3 weeks.

Please bare with me on some simple questions on case forming (it’s my first wildcat)

1. Which die do I use to expand the new 223 case neck to 6mm - the full length resize die or the neck size die?

2. Whichever die from 1 above - will it have a tapered expander plug (Redding dies) or will I have to purchase and install this?

3. If the full length resize die is used to expand the neck to 6mm - do I need to ‘back the die off’ so it does the neck only, or is it ok to full length resize new brass?

4. The inter web has lots of conflicting opinions on ‘crush fit’, ‘false shoulders’, ‘touching the lands’ for fire form loads. My simple thinking is - don’t overthink it, you are just firing a 6x45 in an improved chamber - just load as normal. Advice please.

I’ll post some picks as I take this crazy wild(pussy)cat ride.

Cheers, rathie
Brno Model 2 22lr
Howa mini 6.5 Grendel
Tikka M55 222 Rem
Tikka M55 6mm TCU
20 gauge single shot
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Re: Forming 6mm TCU cases

Post by JimTom » 20 May 2020, 12:10 pm

I anneal and then use a universal expander die to incrementally expand the neck when I sized some 224 necks up to 308 mate. Given that 6mm isn’t that much to neck up from .224, I would think you would be able to do that in one go. Not certain about the rest of your questions so will leave that to those better informed than I.
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Re: Forming 6mm TCU cases

Post by SCJ429 » 20 May 2020, 12:40 pm

If you are moving the shoulder of the case forward there are a number of ways to do it. If you have a tight neck, you neck turn to the point that your new shoulder will start. If not, you can over expand the neck and then use your bushing die to size back down to the new shoulder point. Both of these form a step for your case to headspace off.

The easy way is to load your projectiles long so they are jammed into the rifling. This will stop the case moving forward when the firing pin strikes the primer. See the attached article for more information.

https://www.6mmbr.com/6improvedform.html

For your cases, the angle of the shoulder is increasing but the length of the neck remains pretty much the same. I would use something with a nice tapered button or preferably an expanded mandrel to increase the necks to .270 or what ever your brass necks up to, then add a little neck tension to hold the bullet to only half the lenght of the neck. Then load your fire forming bullet jammed.
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Re: Forming 6mm TCU cases

Post by SCJ429 » 20 May 2020, 12:48 pm

It doesn't matter which die you use, even a 243 Winchester die would do. Redding often have quite a square looking expander ball which is not ideal. Use lots of sizing wax and be gentle if you do it this way. Practice with some throw away cases to see how you go.
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Re: Forming 6mm TCU cases

Post by Rathie » 20 May 2020, 2:04 pm

Brilliant- thanks for the responses.

I’ve read a bit about creating false shoulders.

I’ll try the jamb the projectile into the lands method first - that may be a little easier for a novice.

Will keep you posted. Can’t wait to get shooting with her.
Brno Model 2 22lr
Howa mini 6.5 Grendel
Tikka M55 222 Rem
Tikka M55 6mm TCU
20 gauge single shot
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Re: Forming 6mm TCU cases

Post by Mark » 20 May 2020, 4:12 pm

Just remember that a jamb is instant pressure, So minimum loads to start.
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Re: Forming 6mm TCU cases

Post by Strikey » 20 May 2020, 5:00 pm

The TCU is basically an Ackley Improved case so fireforming would be the same, just neck your cases out to 6mm, load and shoot. Your gunsmith should also set the headspace to be a slight crush on the standard 223 parent case otherwise you may have case separation issues.
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Re: Forming 6mm TCU cases

Post by SCJ429 » 20 May 2020, 10:21 pm

Strikey wrote:The TCU is basically an Ackley Improved case so fireforming would be the same, just neck your cases out to 6mm, load and shoot. Your gunsmith should also set the headspace to be a slight crush on the standard 223 parent case otherwise you may have case separation issues.


Slight crush.?... The case walls get straightened up and you get a 40 degree shoulder. The case will headspace on the new shoulder datum line. I don't understand what part of the original 223 case would you do this to?
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Re: Forming 6mm TCU cases

Post by Strikey » 21 May 2020, 7:52 am

SCJ429 wrote:
Strikey wrote:The TCU is basically an Ackley Improved case so fireforming would be the same, just neck your cases out to 6mm, load and shoot. Your gunsmith should also set the headspace to be a slight crush on the standard 223 parent case otherwise you may have case separation issues.


Slight crush.?... The case walls get straightened up and you get a 40 degree shoulder. The case will headspace on the new shoulder datum line. I don't understand what part of the original 223 case would you do this to?


When chambering for an improved chamber the standard parent case no-go gauge is used as the go gauge or as my gunsmith does is to set the barrel back slightly, 2 thou if memory serves me, the bolt will be slightly tight to close.
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Re: Forming 6mm TCU cases

Post by SCJ429 » 21 May 2020, 12:38 pm

You could use the 223 go gauge on a 223 AI chamber because the gauge will hit the neck shoulder junction. But when your reamer has enlarged the neck to suit 6mm projectiles, the neck shoulder junction has moved and the gauge will keep moving forward until the shoulder width is .270 or bigger.

You will have to make the brass more than the chamber neck size if you want to form a step to headspace off and then use a bushing to size the neck and hold the bullet.
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Re: Forming 6mm TCU cases

Post by Rathie » 13 Jun 2020, 9:45 am

Morning all,

I’ll upload some photo’s when I work out how.

Have just spent an enjoyable hour at the new reloading bench with all my brand new reloading gear necking 223 up to 6mm in preparation for loading and fireforming to 6mmTCU.

The Reddding Custom 3 piece die set arrive yesterday and thank the heavens the button in the FL die is a tapered button.

Necked up to 6mm with no force at all with a vary light lubing on the inside of the necks with Lee resizing lubricant.

Now have 100 cases ready for primer, powder and projectiles. Will wait till I have the rifle back from the smith so I can set the fire form loads to just touch the lands. That seems to be the common recommendation for fire forming.

Have some 2206H, Rem 7 1/2 and Speer 75gn flat base HP’s ready to go.

Fingers crossed - rifle will be ready before a trip to Tenterfield in mid July.
Brno Model 2 22lr
Howa mini 6.5 Grendel
Tikka M55 222 Rem
Tikka M55 6mm TCU
20 gauge single shot
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Re: Forming 6mm TCU cases

Post by Rathie » 13 Jun 2020, 1:29 pm

1488494C-F216-4C0B-A754-75250273968F.jpeg
1488494C-F216-4C0B-A754-75250273968F.jpeg (1.46 MiB) Viewed 4913 times
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44C5782C-CCF3-488B-B51A-C7476CCA8715.jpeg (3.39 MiB) Viewed 4913 times
New reloading bench and a before and after shot of resized case
Brno Model 2 22lr
Howa mini 6.5 Grendel
Tikka M55 222 Rem
Tikka M55 6mm TCU
20 gauge single shot
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Re: Forming 6mm TCU cases

Post by Rathie » 13 Jun 2020, 4:10 pm

5A742751-1342-4265-96AD-E8852B2C9292.jpeg
5A742751-1342-4265-96AD-E8852B2C9292.jpeg (2.22 MiB) Viewed 4901 times
Kissing Cousins. 222 on the left and 6x45 on the right. To be fire formed in 6TCU chamber.
Brno Model 2 22lr
Howa mini 6.5 Grendel
Tikka M55 222 Rem
Tikka M55 6mm TCU
20 gauge single shot
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Re: Forming 6mm TCU cases

Post by marksman » 14 Jun 2020, 9:36 am

sounds like your getting excited Rathie
good for you :thumbsup:
it will never be a chore while you are keen :drinks:
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Re: Forming 6mm TCU cases

Post by Rathie » 14 Jun 2020, 10:58 am

Thanks Marksman.

Yep, has been far too long since I last rolled my own.

First wildcat adds to the joy.

Hope there are some goats about.

Goat curry in a camp oven....
Brno Model 2 22lr
Howa mini 6.5 Grendel
Tikka M55 222 Rem
Tikka M55 6mm TCU
20 gauge single shot
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Re: Forming 6mm TCU cases

Post by duncan61 » 14 Jun 2020, 11:11 am

I have sundays of now I have modified my driving conditions and you have inspired me to sort out my reloading gear since I moved
.22 winchester .22hornet .222 .243 7mm rem mag cbc 12g
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Re: Forming 6mm TCU cases

Post by Rathie » 20 Jul 2020, 9:03 pm

The wait is over! Picking up the Tikka M55 from Swans tomorrow. Will post some picks.

Have picked up an as new Leupold VX3 2.5-8x36 and some SAKO optilock mounts to sit on top.

Start reloading the necked up cases on the weekend.

Have purchased two little clamps that go on a cleaning rod (forgotten the brand name) that will enable me to work out COAL with individual projectiles.

Will load fireform loads to just kiss the lands using mid range 6x45 data.

Full report soon.

Cheers, rathie
Brno Model 2 22lr
Howa mini 6.5 Grendel
Tikka M55 222 Rem
Tikka M55 6mm TCU
20 gauge single shot
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Re: Forming 6mm TCU cases

Post by cqguy73 » 12 Jan 2021, 12:28 pm

How have you found your 6mm TCU. Getting one built soon. Am thinking about getting Swann's to do mine as well. Either that or get a reamer myself and get a local gunsmith to do it.
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Re: Forming 6mm TCU cases

Post by Rathie » 17 Jan 2021, 8:11 am

cqguy73 wrote:How have you found your 6mm TCU. Getting one built soon. Am thinking about getting Swann's to do mine as well. Either that or get a reamer myself and get a local gunsmith to do it.

Have found the whole process very rewarding.

This has been my first experience with a wildcat - so best advice is to ask lots of questions.

Time has been limited, so have not progressed with load development.

Cannot comment on doing the reamer work yourself - way beyond my level of comfort. Swans did a great job and as a small family business are easy to deal with and are good communicators.

With so many factory cartridge options - really need to question the reason for a wildcat. Human nature i guess.
Brno Model 2 22lr
Howa mini 6.5 Grendel
Tikka M55 222 Rem
Tikka M55 6mm TCU
20 gauge single shot
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