Why not 9mm for your character? Start here.
We'll stay retro and Browning and use a Browning HP to compare against our 1911's.
The HP is lighter than both 1911's; 2.4 lbs. Its magazines are the same weight as the .45; 0.5 lbs.
Those magazines hold 13 rounds though!
Rcl is 2, same as .38 Super.
Damage is 2d+2 pi. (2 x 3.5) + 2 = 9 points. Same as the .38 Super on average. The spread is different. 9x19 gets 4-14 of damage, .38 Super gets 2-17. But we're looking at averages here. (Potentially the .45 does the most damage against an unarmored target with a spread of 3-18).
Because the average damage is the same, everything I said about .38 Super here applies to 9mm, but with 4 more shots before you run dry in a lighter gun! 126 points of damage per load. 42 through that DR 6 vest from before.
If the setting allows, change that HP to a Glock 17 and you get two more shots and half pound lighter!
All three guns have the same RoF so comparisons of total damage are perhaps unfair.
With 7+1 rounds the .45 gets two turns with 3 shots each and one with two rounds. The 9+1 of the .38 Super will have three turns of full RoF with a fourth turn getting a single shot. 13+1 gives four of full rate and a remainder with two.
All three guns reload in 3 turns. To fire 14 rounds the .45 will need 9 turns (reload turns being 4-6). The .38 Super also needs nine (with the reload happening in turns 5-7). The HP needs 5 turns. A Glock also needs five turns, and has four shots left!