ihmsa forums

Sorry, but got another question.

I am trying to get my 7TCU brass ready to load. I couldn't find any good instructions on setting the die for initial forming of this case. How much do I need to back the FL die off for the initial sizing? Don't want to push the shoulder back too far. Also the couple that I tried are about .02 or so short of the case length in the manuals. Now I'm sure the case will stretch on the initial firing to close to the recommended length and then then might need trimmed to length.
And then, what would be a good load for fire forming?

Thanks for the help. It's a pain trying to get back into this again, but I know it'll be worth it.

when i shot a 7tcu i sized the brass just enough to chamber and locked it with the lock ring. that way the sized brass fit snugly in the chamber. no reason to fireform the cases. just pick the load you want and shoot them. allen

You can also use 222 Rem Mag brass (hard to find sometimes) or use the new 204 Ruger brass to make your TCU cases. You can adjust your size die down in small increments until you get a snug fit and will get perfect formed brass the first time. Using these two cases will also allow you to get correct length brass. Most all .223 and .556 cases will come up short and will never grow to max length. If you use 204 Ruger brass, you may need to take a tapered punch and lightly expand the .20 cal neck to get the tapered expander to enter the case. I would suggest trimming the new brass to max length and then check again after fire forming since the cases may actually get shorter by a few thousands when the case blows out.

If you desire using the 100 and 120gr 7mm bullets you may want to go the 222 Rem Mag route. Remember that 7-tcu chambers seem to be laws unto themselves. What chambers in one barrel may be refused by another. Segregate your cases if you have multiple barrels. Check several cases for proper fit before assuming your dies are set properly. Make a dummy round to check proximity to the lands. Keep records on your finished length so you know what fits each barrel. Power trimmers such as the Lyman are a blessing. rp

As mentioned above there are very few 7TCU barrels that will allow you to mix ammo between them.
When I first started fooling with the 7TCU I was "informed" that milsurp brass would cause me nothing but problems. My findings were actually quite the opposite. Wilsurp brass being some what thicker by a smidge took up some of the "slop" that TC gives at no extra charge. Yes you might have to anneal which is not a bad thing, none the less my end results were enough better I never used anything but milsurp cases. The last 7TCU barrel I had and parted with had over 500 pieces of brass with it. All LC and sorted into lots by year. They had all been loaded over 25 times, neck sized about three times then bump the shoulder. FYI, they were all a bit under length, as mentioned above.
I did fool with some 222 mag. I found no difference in accuracy with a smidge longer neck. Just as long as they are ALL the same length.

As to the fireforming. I would not trim until after fire forming. Unless you go the 222mag. I found a large majority of the cases grew un even and case mouths just needed to be squared after fire forming, why trim twice?

748 and AA2015 was my go to powder.


About forgot. Do not push the shoulder back. If cases are short for chamber you will have problems. Engauguing the rifling on a fire form load will hold the case back agaginst the breach and help with a proper fire forming. Ican show one easier than typing here. A crush fit against the shoulder is what some try to achieve.

According to my copy of "Reloading Guide for Handgn Accuracy":

When you die-form your parent cases, adjust your sizing die so that the shuolder of the case is about 0.010" too far forward to fit into the gun's chamber (the action will not quite close). Then, very GRADUALLY turn down your die in the press (about a sixteenth of a revolution at a time) until the shoulder of the new case is moved back just enough to let the action close.

Ideally, you want about 0.003" headspace between the shoulder of the die formed case and the chanber's shoulder. If you wish to work to this level of precision, yau may use two thicknesses of Scotch Magic Tape (or any other whose thickness is 1.5 mils) adhered to the head of a test case. Together, two pieces of this tape are exactly 0.003" thick, and may be used as a headspace guage on your test case. Your gun's action, at this point, should require a moderate force to close.

THE ABOVE IS VERBATIM FROM THE BOOK, PAGE 55.