Never found 9mm to be any more difficult than any other pistol caliber cartridges. In the mid 70's, I purchased my first two handguns, days apart. Colt Python and a Browning HP. Learned to load both, simultaneously. At first it was jacketed bullets, eventually moving to strictly cast, a few years later.
Only difference between the two cartridges is the type of crimp used. Usually a roll crimp for straight walled, revolver & carbine, cartridges. Taper crimp for semi-autos. There are some exceptions. Everything else is pretty much straight forward.
Finding loading data for jacketed is easy. Most manufactures put out their own loading manuals. Cast data, not so easy because of the variations of designs................not to mention all the numerous mold makers.
COAL in the various manuals is just a starting point...........not set in stone. Especially, when it comes to loading cast. You must determine what COAL works for your particular firearm/firearms. Personally, I don't measure COAL. I go by O-give measurements, which are much shorter, and stay constant, once determined. Bullet design doesn't matter, with O-give measurements. However, I like to stick with TC or RNFP's and nothing over 138 grains. Only reason for heavy for caliber is for suppressed firearms. I own five 9mm semiauto pistols and one carbine..............all different manufactures. None have been throated. All of my ammo will operate in every single one. Not about to keep separate specific loads for half dozen firearms. I'm not target shooting with 9mm. I view it as a up close and personal defensive round.
It ain't rocket science to determine what length you need. A good starting point is measuring factory ammo (O-give) with similar bullet designs and weight then comparing that to the same designs in cast. Make up dummy rounds and record length (I mark each case with a Sharpie).........good time to do a plunk test. If the round passes, load magazines and manually cycle though action..............then check to see of the length changed.
Factory ammo works in all the tens of millions 9mm's in circulation. Impossible to tailor a load for a specific firearm.
Here's a O-give length comparison of some factory 9mm ammunition, I've had on hand:
Blazer 115 (FMJ) .888 - .894
Federal 115 (JHP) .878 - .928
Hornady Critical Duty 115 (JHP) .840 - .841
Hornady Critical Duty 135 (JHP) .859 - .863
Hornady XTP 147 (JHP) .891 - .891
Golden Sabre 124 (JHP) .959 - .963
Speer Gold Dot (JHP) .916 - .919
Win Silvertips 115 (JHP) .880 - .884
American Eagle (115) FMJ .895 - .896
American Eagle (147) FMJ TC .876 - .888
Even factory ammo, out of the same box, exhibits variations in length, yet operates in millions of firearms. Again, it ain't Rocket Science. Don't even get me started on brass. I've loaded most, without issues. I do separate by headstamps, but that's about it. However, I do prefer Blazer reloadable brass, when I can get it.
BTW, I started off casting with the RCBS 125 RN GC. Used that bullet exclusively, for many years. I used a O-give length of .865 which falls within the parameter's of the above factory loadings.