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  #1  
Old 05-20-2020, 12:51 AM
jawry jawry is offline
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Default Case forming 6mm TCU

Morning all,

Have myself a fine little Tikka M55 at the gunsmith having a 24” 1:10 twist 6mm TCU fitted.

This is my first ever wildcat (or pussy perhaps in the case of the TCU?)

Have a 3 piece Redding die set ordered.

A couple of simple questions on case forming please.

1. Which die do I use to expand the necks from 224 to 6mm - the full length or neck size only die (told you I was a virgin)

2. Whichever die it is - will the ‘expander plug’ be tapered, or will I have to purchase/fit and tapered expander?

3. If it’s the full length resizing die - do you need to ‘back out’ the die so it does the neck only, or is it ok just to full length resize the brass. Incidentally - I’ll be using brand new 223 cases to form the TCU cases.

4. The internet views of ‘crush fit’, false neck, touching the lands is contradictory and confusing - for my mind I’m simply firing a 6x45 in an improved chamber (TCU) - don’t overthink it and just load the case as normal. Advice please.

That should be it for the moment - but I’m sure to be back and report on progress (and have some pictures) as I take this crazy ride.

Oh, she will be a general purpose rifle that will see duty as a walk about rifle for goats, pigs, Fox, wild dogs, rabbits etc.

Last edited by jawry; 05-20-2020 at 01:00 AM. Reason: Spelling
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  #2  
Old 05-20-2020, 02:42 AM
SEM SEM is offline
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you will have to see if the die set comes with a tapered expander most likely does, the false shoulder does help considerably when fire forming, seated to the lands does work too just not as precise, I go about it the hard way and make my TCU brass from Starline basic 223 brass, a lot more steps to get to 6mm but worth it in the end, I end up with a case length that matches the chamber and is as close to fire formed as you can get with out going bang

Welcome to the TCU club now you just need a 257 a 6.5mm a 270 and a 7mm
a 223 AI is almost a 224 TCU and there are some 30 and 338s that are real close and yes I have most, just lacking the 223 AI
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Old 05-20-2020, 02:44 AM
Johnly Johnly is offline
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I have several 6mm TCU barrels and just run fired 223 cases into the FL die until I can close the action on the partially sized case. My dies are Hornady brand, but most TCU dies have a tapered expander as the manufacture knows that 223 cases will be the feed stock.
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Old 05-20-2020, 11:10 PM
DAVID DAVID is offline
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I shoot a switch barrel Remington M7 in the following cartridges:

6mm TCU

257 TCU

7MM TCU

30 TCU

ALL cartridges are loaded with the same Wilson hand die, with only a change in neck size bushings per cartridge. Bullet seating dies are Hornady "short" Universal bullet seating dies.

4 cartridges / 4 barrels - and even the scope does not have to come off to switch out barrels!

I use Winchester brand 204 Ruger brass for all 4 cartridges.

I use the Hornady Elliptical expander buttons to expand the case mouths up to the appropriate caliber. I will also take a Q-Tip and put a little bit of Imperial Size Die Wax on it, and run it into the case necks to make the expanding operation go much smoother and easier.

Even in my factory TCU Super 14" and carbine barrels, I use 204 Ruger brass in them as well, and it gains me another tenth of an inch in neck length, with the cases needing trimmed just enough to square up the case mouths.

I hope you enjoy your new 6mm TCU rifle, as they are deadly accurate, very mild in recoil, and just flat out fun to reload for and shoot! I have killed a lot of deer with my 6mm TCU, as well as a few coyotes and a big pick-up truck load of crows!

Let us know if you need any more help in the forming or loading of your new rifle, as I'm sure there are several of us here that would be more than glad to help.
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  #5  
Old 05-21-2020, 01:03 AM
jawry jawry is offline
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Thanks so much everyone for your sage advice.

Iíll probably load the necked up 223 brass with the projectiles just touching the lands for the Ďfireformí loads. Use a mild load to start and see how that goes.

If Iím way off track please feel free to yell STOP!


Should be back from the gunsmiths next week and dies should arrive from the US shortly.

Lots more questions to come - Iíll return the favour with some photoís.

Now to buy a scope and mounts. Thinking a Redfield 4-12x40 in some Talley lightweight alum mounts??
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  #6  
Old 05-21-2020, 04:54 AM
DAVID DAVID is offline
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Your fireform loads should jam the rifling to help minimize headspace.

For the favorable reloading manuals that do have 6mm TCU load data listed, use at least a "middle listed load" to help make sure the case fully forms to your chamber! Meaning that the shoulder angle is not rounded, but almost sharp and we'll defined.

Only AFTER your rounds have been fireformed, do you trim all cases to the same length and square the case mouths. And of course, you deburr and chamfer the case mouths slightly.

After all your rounds have been fireformed to match your chambers dimensions, unless you get heavy handed at the powder scale, do NOT push the shoulder back on your cases! Back your size die a couple of turns away from the shell holder, which should allow for sizing 2/3rds. of the case neck length, which is more than enough for adequate case neck tension.

Something that I have done with all of my TCU barrels, is take "1" cartridge and after fireforming, load it in half grain increments, checking for signs of excessive pressure. When maximum pressure is reached, I would drop the powder charge one full grain and call that my "safe maximum load". Once you know what your guns safe maximum load is, you can load at that charge weight, then start backing down your loads in 3/10th. grain increments, looking for your guns most accurate load.

With my barrels, when I hit the maximum load, bolt lift was ever so slightly more than normal, or what it felt like on an empty chamber. At this point, I began sizing the neck down just a few thousandths at a time, just until there was no longer any bolt lift resistance. This allowed for absolute "0" headspace, long case life, and best accuracy. I set up every gun I own this way.

Another thing that I always do, is seat the bullets out to touch the rifling, and with any and all loads. I don't shoot VLD bullets or any other "match" type bullets, which usually do shoot better when the bullet has as much as .030 to .040 or more jump before making contact with the rifling.

Like the old adage, guns are like people and no two are exactly alike, so you just have to find out what YOUR gun likes best!
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  #7  
Old 05-22-2020, 01:00 AM
GrocMax GrocMax is offline
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Use CCI 400's or std thin more sensitive primers, and a moderate powder charge on FF loads and you don't need to do anything else but load and shoot just leave a bit of a crush fit shoulder to neck, size them slightly long. Until the shoulder is established avoid CCI BR-4's, 450's, or 41's, and 7 1/2's, just asking for problems.
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  #8  
Old 05-22-2020, 02:38 AM
JSH JSH is offline
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All good advice that I can add little too.
Things I have found out, jam or crush fit will not always guarantee a nice fire formed case. I have come to the point I anneal and end up with well formed cases, with a crush fit. Jam definitely raises pressure and insures growth will keep head separation to a minimum.

Fire forming loads 9 times out of 10 will give some really decent groups. I donít look at them as a waste of components.

I use virgin brass and have very few issues. I still anneal these.

Imho this is a great cartridge that is looked over by many.
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