Fire Forming TCU Cases

[centershot]

I have a .223 Ackley. You can shoot standard .223 rounds in the Ackley chamber and not worry about head space. I am building a 6mm TCU rifle. It has a 40* shoulder. Do I have to seat the bullets to the lands in order to maintain proper head space on fire forming or is it like and Ackley?

 

[watercam]

I had a 7mm TCU and had no issues simply loading and firing with normal bullet jump. Worked up my load up to maximum and ended up with fire formed cases at the end. Velocity change before and after was not significant and when I re-tested my chosen load accuracy was still good.

 

[JEFFPPC]

I would seat the bullets to make hard contact with the rifling. That his how I fire formed cases years ago for a 6 TCU 14 inch Contender with a 12X Leupold. With a case full of 748 and a 60 gr. Sierra HP it took a very good rifle to be more accurate. Shot little holes.

 

[centershot]

I had a 7mm TCU and had no issues simply loading and firing with normal bullet jump. Worked up my load up to maximum and ended up with fire formed cases at the end. Velocity change before and after was not significant and when I re-tested my chosen load accuracy was still good.

What were your favorite powders?

 

[Ggmac]

I've got many 6tcu , I do load long jam for the first load . If I don't I find case life short . I get 8-10 loads on a case if I jam , I use a flat base 70 gr Speer and a2220 powder , after that I use 4198, benchmark , 8208 , 4895 , varget . It is a very easy and forgiving cartridge .
Sorry had a brain fart on bullet weight , it's a 70 Speer TNT

 

[GrocMax]

Alternately when you set up your die for the first neck/shoulder forming, set it up slightly long so the bolt closes snug but not overly tight. New brass works best. Then use a stout 6x45 load with a CCI 400 or other primer without a thick cup, put the bullet where it shoots best. You'll get consistent length, sharply formed cases without CHS issues. Hard/thick primers on fireforming can cause issues down the road, do not recommend 450's, BR4's, Tula SRM/5.56, 41's.

A start load for 6x45 is usually not enough for a fully formed case, near max for 6x45 is safe and gets it formed. Accuracy can be very good when you have the option of moving the bullet around, unless you get lucky.

 

[centershot]

I've got many 6tcu , I do load long jam for the first load . If I don't I find case life short . I get 8-10 loads on a case if I jam , I use a flat base 52-53 gr and a2220 powder , after that I use 4198, benchmark , 8208 , 4895 , varget . It is a very easy and forgiving cartridge .

I was thinking of using TAC powder. Anyone try that?

 

[Shaggy357]

The old standard load for forming 7TCU was 8.0 grains of Unique and an RCBS 145 Silhouette cast bullet sticking out far enough that you could just close your action with the bullet against the rifling. Came closest to fully forming the case, and was an accurate round to boot. My forming loads for 6 TCU is the Nosler 70 grain BT with a moderate load of H322. Seat the bullet out far enough for it to engage the rifling. On some guns, this may be a stretch....literally, they have really long throats. You may have to go up to a 90 gr bullet. These forming loads are good hunting loads for chucks, coyotes, etc, but are usually a little too light to take on deer or antelope. If I was in a pinch, and wanted to get something loaded full house right away, I use 7TCU brass and size it so it just fits my 6.5 or 6 TCU chambers. This has worked well for me. Now you know why I started off mentioning 7TCU...they are cheaper to form and can be sized for the smaller calibers.

Hope this helps.

 

[Ggmac]

I've edited my post , I made a mistake in bullet weight , I use the flat base 70 gr Speer , jammed

 

[fredo]

I have a .223 Ackley. You can shoot standard .223 rounds in the Ackley chamber and not worry about head space. I am building a 6mm TCU rifle. It has a 40* shoulder. Do I have to seat the bullets to the lands in order to maintain proper head space on fire forming or is it like and Ackley?

No need to jam. As Grocmax mentioned, just neck virgin .223 brass up to 6mm, and make sure you're getting that slight 'crush fit' when closing the bolt. Then find a decent FF load and shoot 'em up!

Here's a 6x45AI case (near twin to 6TCU) fireformed from Winchester .223 brass, nice crispy shoulder! That case was formed with H322 / 87Vmax, jumping ~.015"

And that's what an 80TTSX broadside exit hole will look like on a whitetail...

That's a GREAT little case, have fun with it!!!