Chris, please bear with us.
As Brother Rich alluded to, when we see post that are somewhat “disjointed” it makes it difficult to be concise in response.
We can only respond to what was “written” not what you thought you wrote or said.
We may be confused due to several points
As Rich mentioned, ALWAYS mention caliber as your bullets grain weights can be loaded into several different caliber cases and wildcats as well.
It is also helpful to list the COL you will be or wanting to be seating these bullets too.
As well as firearm these loadings will be used in.
(This can affect recommendations on charge weights and other factors in your loading)
You asked “Any ideas of where to find proper Starting Loads and DNE Loads or how to determine them on my own?
If you are loading for the 9MM Luger, this data is available on the Hodgdon web site?
115 GR. LRN Win AutoComp .356" 1.100" Start 4.4grs 1002 24,800 PSI Max 5.1grs 1145 31,500 PSI
125 GR. LCN Win AutoComp .356" 1.125" Start 4.3 grs 1012 26,700 PSI Max 4.8grs 1101 32,800 PSI
The data above from the Hodgdon web site list starting and maximum charge recommendations for both the 115gr and the 125gr Lead
This data can be applied to your 120gr. lead bullet.
Here you can play it on the safe side and use the 125gr. data
You asked “how to determine them (starting & max) on my own?
This is done through the “workup” routine.
Begin at the starting charge weight, increasing in a 10th of a grain increment toward the maximum listed charge weight.
(Make 10 and test before any increase in charge weight)
When “working up” the loadings, monitor for trouble signs and excessive pressure signs.
This protocol, and other “techniques” regarding safe loading procedures are clearly explained in ALL loading manuals.
(You DID read your loading manuals, right?)
For your AutoComp in 9MM, Hodgdon list data for the 147gr. but in a jacketed bullet (Hornady XTP)
All is not lost here, using the jacketed starting charge weight data would be safe to apply to your lead 147gr bullet.
147 GR. HDY XTP Win AutoComp .355" 1.100" Start 3.6grs. 827 27,900 PSI Max 4.0grs. 916 32,800 PSI
Another option for you would be to apply a powder or powders that have more “development data” available for the bullet(s) type you are using.
On the faster powder side, powders like Bullseye, Titegroup, AA No.2, AA No.5 V-V N320 and 231 will have more abundant data available.
On the slower side, powders like HS-6, Power Pistol, V-V N340, V-V N350, AA No. 7 and Blue Dot.
(The AutoComp is designed primarily for using jacketed in high performance application.)
This is why you will not see “reams” of published load data with the lead bullets you have using this powder.
Good Luck