300BlkTalk

I have a Lee set up with the Breech Lock Pro. I am using once fired .223. Cutting the brass with the HF chop saw and jig, resize it with the resizing and depriming die. I put the freshly cut casing in my Wilson gage checker and all the cases do not fit flush (once fired 300BO <Sig, AE subsonic and S&B> all fit and fall without issue). I took the calipers and ran them down the body, and the body gets wider at the base. l.C. Brass measures 0.3745, while the F.C. brass measures 0.3740-0.3745. When putting the once fired .223 cases in backwards to the gage, they all go in, no problem...maybe it’s the shoulder? Let’s cut a newly formed 300 BO at the shoulder and see if it fits flush..nope. It slips all the way in and needs to be push out from the other end. I tried moving the die up and down to make contact with the plate sooner and later, no fix. Any ideas? Get a new die? Getting a bit frustrated here...damn California liberals.

Although I have a set of lee dies, I only form with my RCBS die.

That being said, you need to start off with the "good" brass. If you use "bad" brass, you will soon learn that all your work/time spent was wasted.
So check the headstamp against the thread that lists the brass to use and the brass to avoid.

Sometimes, shell holders interfere with the die making it far enough down the case for a "complete" resizing. Some have milled the shell holders/plates thinner and some have found one manufacturer's are thinner then another.
If you also load .223 ammo, you can resize with your .223 die then cut it off and then form the shoulder. Adds a step, but requires less force per step. Again, I have done it both ways but only with RCBS dies.

So I guess I am hanging my hat on the dies/shell holder try RCBS and see if the problem goes away.

Thus the need for Small Base Dies ie. RCBS SB 300 blk dies

It sounds more like a length problem than diameter. You don’t mention trimming to length, is it possible the sized case is too long and that is your issue?

If you have a Lee sizing, that is another known problem. Lee does not suggest you form with them. Depending on how much they are sticking out of the gauge, you might be able to slide paper or card stock under the case in the shell holder and a few thousandths more setback on the shoulder.

Last but not least, forming on a progressive press is a not the best idea. Too much stress on the press and in general progressives have too much flex. You end up with poor quality brass and wearing the press out sooner than normal. That also may be part of the problem.

Heya guys, great information, much appreciated, not completely what I wanted to hear, but great none the less. I trimmed the brass to 1.3565. The spent F.C. casing I have is measuring at 1.3540. I cut a couple L.C. cases at 1.3530, 1.3560, and a couple at 1.3565. All had the same problem. After reading some of the comments, it is prolly the die. I don’t think it’s the press just yet since this is the first casing I am trying to reload.

RCBS threading comparable with Lee threading?

Yes, the threads are the same. 7/8”x14 is considered standard.

Your easiest, fastest check/fix would be shimming under the case. That will lift it into the the die farther. If you take a failed case and measure how far it sticks out of the gauge before and after, you will have your answer. You can use paper or card stock. You can also build up layers of scotch tape. If that shows promise then you can decide if you buy another die.

The Wilson gauge is designed to measure fired brass, so the diameter of your formed cases does not come into play. Likewise, total length of the case is not important; if the case is too long, it just pokes out the other end. The only thing that matters with the Wilson gauge is the distance from the base to the shoulder. Obviously your die is not setting the shoulder back far enough.

Set your die where the shellholder is making firm contact on the upstroke. Then look while you size a shell. If the shellholder is NOT making contact, then your press is flexing. If it is, then the die sucks (more likely).

When you buy a new die, you don't need a small base die. You just don't.

Best thing...ignore all the above and just get a new quality sizer. Money well spent, for getting a real lock ring if nothing else. Midway has the Forster on sale right now.