Visual difference using Lee-U die.

Problematic? 2 are with Lee undersize. 2 without. I imagine you can see which are which.

All plunk in barrel and in headspace gauge

I did not anticipate THIS big of a difference. Can be felt with a bare finger tip.

I will keep the U die for future loadings... but I didn't think it would be this undersized. Maybe my standard sizer really was larger (yes, i took measurements, but did not write down. I can add to the thread in a few min when I am home again).

Any problems here other than lots of extra work on the brass?

I was having some setback issues on a few cases per 1-200. I was trying to eliminate those as even a pressed bullet will fit in my chamber. Trying to eliminate that issue. I did go through my whole setup and got it to where I was SIGNIFICANTLY reducing bullets likely to set back, but was still getting a few using mixed brass.

LOL 243. Left 2 are with the undersize die.
I am curious if it will change my preferred load/pressure. I am not loading hot. Middle of the road Titegroup over 124grain Xtreme plated or Hornaday FMJ (different load weights)

243winxb said:

The U die will cut the case capacity a tiny bit. Not enough to matter, is my guess. Mixed brass may make more of a difference.

RCBS has said its possible to "neck size" the brass, stopping just below the bullets base. This did NOT work for me with 45 acp.

But i dont size as far down as possible. I place a nickel coin between the shell holder and bottom of the carbide die to adjust/set . I feel this gives the case a better fit in the chamber. Remove decapping pin first.

Click to expand...

Case tension on bullet non-factor. I am not a heavy crimp guy. Nearly nil. if any, just enough to remove a rough edge at the case mouth

Those are all Blazer. Those were the cases I was having problems with setback with. In my area/at my range, there is a TON of blazer. We are close to a cabelas that usually runs it under $12 a box. So many people run it (and I pick it up)

The smaller ID from the U sizing die is where I was anticipating gaining my neck tension. I do NOT crimp to try to reduce setback. Just to clarify .

I should have had a ? mark on my last post above. It was a question... that the tighter case ID and increased tension shouldn't make a large issue on pressures at medium loads?