Both ~251 grains with my alloy (3:1 lead:lino + tin).
The Ideal mold (2-cavity iron) drops at .433", the Lyman (4-cavity iron) dropping at .430".
Both relatively the same length. The Ideal has a very slightly wider meplat.
Base band is thicker on the Lyman.
The Lyman has the square grease groove and a very nice angled crimp groove. The Ideal has the rounded grease groove and no angled shoulder on the crimp groove. Not sure how well this will show up with my cell pics.


Ideal



Lyman
capital one bank branch near me

The .433" Ideal would be just the ticket for some revolvers I have whose cylinders have generous throats.

Twenty five + years ago Veral Smith fixed me up with some custom molds so those handguns would be happy.

Mathman
That's my situation as well. The .430 Lyman isn't useful for my 29-2. I do however have a 24-3 coming in a week or so.. we'll see what throats it has.

I like the round lube grooves, drops easier from mould.
both shoot very well for me.

I’ve been casting and shooting the Lyman 429421 two cavity for about 35 yrs. in both 44 Special and 44 Magnum with no problems. My bullets drop from the mold at 251 grains and size at .431. I also have an RCBS 44-250 on the shelf that I haven’t used yet, but it promises to also be a good one if it sizes good as cast.

Lyman molds are constantly evolving. Case in point: #225438, the nigh perfect .22 Hornet cast bullet. I have four of them, the oldest being a truly ancient Ideal and the newest being only a couple years old and they are all very different, but still nearly the same weight/length/shape. The rifles I shoot them in refuse to nominate any one of the bunch as "best".

Today I cast and powder coated another variant of the 429-421, this one a 5-cavity aluminum from MP Molds, the HG503-432.
I forgot to take a pic before powder coating. The powder is Smoke's Traffic Purple.
257-258 grains each after coating. Sized to .432. Powder coat on this badge is a little lumpy, Not sure why.

In an Ideal world they will both work. No Ly man.

Was there a question ?

I haven’t gotten into powder coating. I probably won’t, since LBT Blue Soft works so well in my handguns.

And, at 78 I’m getting too old to try anything new.

Not that you need to try anything new, but this thread illustrates one of the benefits of powder coating. If your mould drops bullets that are too small in diameter with your preferred alloy, it's simple to powder coat them to make them larger. If you've got a Lyman 429421 that casts at .430", but your gun prefers .432-.433", a good powder coat will make them the perfect size. Just one of the many possible benefits of powder coating.

Again, not a required skill, but I've found it indispensable for solving some problems.