Lloyd,
I have had similar troubles with my Lee 405 grain mould; however, I found that if I hold the bottom of the mould blocks together with a gloved hand whilst the other hand is opening the handles, the bullet falls out on its own every time.
Try that bullet (tumble lubed) over 34 grains of IMR 3031 and a small piece of Dacron wadding in your guide gun. It will cut a 5-shot one-hole group for me at 50 yards with a Williams peep sight. No recoil to speak of, no leading. My bullets for this load are waterdropped ww.
I've been working on a load with that bullet that I haven't chrono'd yet...using 3 grains of bullseye and a soft lead bullet. At 100 yards, after you fire, you should have time to put the gun down, swig on your coffee, pickup your binoculars, adjust the focus, then watch your bullet impact at 100 yards. Good entertainment!
I tried 1.5 grains of Bullseye, but I stuck a bullet 3/4 the way down the bore. I'm convinced this will work with a soft-enough lead bullet and a clean bore, but I haven't been successful with it yet.
Have you shot any of the .458 bullets from your other new mould yet? Give us a report when you do.
The Blade