Here is the problem, I am fire forming 223 cases into 7mm TCU. But Having problems with ignition, I am leaving the bullet stick out from the case ALOT . Do you think the bullet sitting in the lands could be taking up some of the firing pin impact? I was hoping it would hold the rimless 223 case against the breach face to fire form the case?

You do not mention what firearm you are using?
AR,Contender?
The case cannot move from the firing pin strike while fire forming.
Is there any shoulder at all on your case?

From the Hornady Reloading Manual, 5th Edition;

"Cases are formed from the 223 Remington, using standard 7mm TCU dies and a tapered neck expander. After neck expanding, a starting load is used to fire form the new case. These starting loads are usually accurate and good practice loads. Commercial (as opposed to military 5.56mm) brass cases work best for reforming."

I form a lot of .357 Herrett cases and the key to those is to set the die where the Contender will just shut, then move it down ¼ turn to ensure the case is held in the chamber properly. This is presuming you are using a Contender.

I am shooting a Contender.

I am just concerned with fire forming, so no the only shoulder that is there is what is left from the 223 case and is 23 deg.

With the herrett there is a rim, none on the 223

Do you know what your max COL is? Could be you have a very long throat and you are not holding the case back. This can be a PIA with a Contender because you go from closing the action to not closing with only a few thousands.
You might need to go to a longer bullet like a Barnes to get something long enough to hold the case back.

My Full length die, if contacting the shell holder, pushed the shoulder back way to much on forming. A firing pin stike can push a bullet into the case, if neck tension is light. The strike can also set a 223 shoulder back as much as .006" also, but maybe not in a contender. Size just enough so the action will close, no more.

What do you think? should I stick with the Manual recommended COL, or set the bullet out to engage the rifling?

quote:

Originally posted by 243winxb:
My Full length die, if contacting the shell holder, pushed the shoulder back way to much on forming. A firing pin stike can push a bullet into the case, if neck tension is light. The strike can also set a 223 shoulder back as much as .006" also, but maybe not in a contender. Size just enough so the action will close, no more.

Same as with the Herrett.

I'm assuming you're annealing to expand 223 to 284? How hard do the bullets seat? Yes, you want the bullets seated out hard into the lands, so the case head is held against the frame. The poor ignition is from the pin driving the whole case forward instead of denting the primer. You could try expanding more than 284, then neck back down in the TCU die to create a little shoulder. There are probably hydro forming dies that could blow out the shoulder too. You could also cut some little rectangles out of coke cans and shim behind the TC ejector so it helps hold the case back.

You'll have to experiment, but that's part of the fun!

quote:

Originally posted by DLH4570:
What do you think? should I stick with the Manual recommended COL, or set the bullet out to engage the rifling?

You need to find your max COL.
Drop a bullet in the chamber and hold it forward with a dowel or pencil and at the same time insert a cleaning rod that has a flat end (I have a screw that threads into mine that I have ground the head flat on) in the muzzle and make a mark on the rod flush with the muzzle.
Now take the bullet out and close the action and insert the cleaning rod in the muzzle until it is against the breech and mark the rod flush with the muzzle again.
The distance between the marks is your max COL for that bullet.
Put together some mild loads with the bullets seated to this COL and they should fireform fine.
If that doesn't work let me know. I have some of 7TCU brass and don't shoot my contender much any more.