I don’t think slower is the direction you want go in a semi automatic pistol. These are short recoil mechanisms, barrel pressures push against that cartridge case at unlock. High unlock pressures will accelerate that slide. Accelerate that slide to where you have mechanical issues.
I had a Colt Combat Elite peen its frame out with about 3000 rounds. It was due to a factory defect, it unlocked early in the pressure cycle and that slide just slammed hard against the frame. Colt replaced the frame but did not fix the early unlock. It took the M1911 experts at Wilson Arms to fix the gun.
It is my considered opinion what you want in a M1911 is a fast burning powder that provides a sharp kick but a fast pressure drop. A low pressure at unlock is easier on the mechanism.
As an example of a “bad” powder, based on Gunwriter recommendations (darn shills) I tried Blue Dot with a 230. Cases ejected about 25 to 30 feet away, recoil was real hard. Even for 800 fps loads. I believe Blue Dot gives high residual barrel pressures after unlock. Blue Dot might work great for something like a Thompson Machine Gun, that thing has a huge breech block, might work better in artic conditions, but high pressures at unlock will peen a M1911 frame in short order.
I don’t believe W231 is a slower burning powder than Bullseye, or at least not by much. It is an outstanding powder with a 230 LRN. I have used anywhere between 4.6 grains, which are powder puff loads but function the mechanism, up to 5.5 grains. I prefer 5.0 grains with a 230 LRN.
My Unique data is below. Unique is a great powder and will work well in the 45 ACP. For my pistols I would use 5.5 grains. Someone with a SIG (I think) tried 5.5 grains and it would not cycle his pistol.
Bullseye was the first powder used in the 45 ACP, going back to at least 1910, and it is still my favorite M1911 powder.
Code:
Kimber Custom Classic
230 gr LRN 4.5 grs Bullseye Mixed Brass WLP
21-Jun-06 T = 97 °F
OAL 1.250" taper crimp .469"
Ave Vel = 805.2
Std Dev =11.4
ES=54.08
High=836.9
Low=782.8
N =32
230 LRN Valiant 5.5 grs Unique lot UN331 1989 Mixed brass WLP (brass)
OAL 1.250" taper crimped 0.469"
16-May-09 high 83 °F
Ave Vel = 827.4
Std Dev = 17.63
ES = 85.68
High = 871.6
Low = 785.9
N = 31
230 LRN Valiant 6.0 grs Unique lot 6/21/1998 Mixed brass WLP (nickle)
16-May-09 high 83 °F OAL 1.250" taper crimped 0.469"
Ave Vel = 885
Std Dev = 16.79
ES = 67.26
High = 917.8
Low = 850.5
N = 30
accurate lots recoil15' foot ejection
230 LRN 6.5 grs Unique lot UN387 6/21/93 Mixed brass WLP
OAL 1.250" taper crimped 0.469 "
18-Mar-07 T = 62 °F
Ave Vel = 926.4
Std Dev = 16.64
ES 71.16
High 963.4
Low 892.3
N = 32
light leading accurate centered hard recoil 20 foot ejection