As many know, I have long been a fan of older steel sizing dies for revolvers as they resize the brass less and thusly fit the cylinder charge holes better.
I have been using a 1957 (I) RCBS sizing die in 45 Colt for some years. I ran accross an orphan 45 Colt Pacific Durachrome sizing die for less than $10.00 and had to try it. Pacific does not date their dies, but it is as old if not a few years older youngrt than the RCBS. After cleaning both dies, I sized two identical W-W 45 Colt cases and took some measurement for comparison. Here are the numbers for what they are worth.
RCBS
Mouth - .4720
Mid case - .4790
Base - .4800
ID Mouth - .4500
PACIFIC
Mouth - .4710
Mid case - .4760
Base - .4770
ID Mouth - .4475
I used and old Pacific upstroke press and it was evident by feel the RCBS die was sizing less. The principal difference was the sizing at the case mouth and the inside diamter of the sized case mouth.
Not allot difference, but perhaps enough to give the brass longer life as the case mouth does not size and then expanded as much to receive the bullet.
I also have a 1977 RCBS steel die and it sizes more than both the Pacific and the 1957 RCBS. At any rate, I will use continue use the RCBS. This is just a little drop of knowledge to add to our lake of common knowledge.
BTW - I use an old RCBS expander that measure .451. This is the way they came before jacketed bullets appeared on the market.