Let me address a couple of points that may not be clear from the previous posts.
Your Colt LW Commander and dave 45-90's STI 38 Super Comp have about as much in common as my S&W 686 and a Victory model 38 S&W Long. The only thing they have in common is they will accept cartridges with the same dimensions.
Brass..........
So far no one has mentioned the 38ACP (not to be confused with 380ACP). It's the cartridge that morphed into the 38 Super. Dimensionally identical, 38ACP brass should not be used for loads using data recommended for 38 Super.
9mm Largo and 9X23 are one and the same; two names for the same cartridge. There has been lots of 9mm Largo ammo imported through the years so there's brass still available. When USPSA banned major power factor loads using 9X19 brass, Winchester introduced the 9X23 Winchester to compete with the 38 Super which was the preferred hot rod cartridge at the time. Their first effort wasn't strong enough and many failures resulted. After a couple of redesigns they got it right. 9mm Largo and original 9X23 Win brass should not be loaded to current major power factor levels.
The exception to all this is......Star Line brass can be used with any reliable data up to +P+ levels.
Barrel dimensions...................
The original 38ACP was neither a 38(.357) nor a 9mm(.355). It split the difference with a .356 groove dia. That probably contributed as much to its reputation for poor accuracy as the semi-rim. When USPSA Open Division took off and buyers were asking for the latest cartridge-of-the-month, the specialty gunsmiths started ordering 9mm barrels and chambered them for whatever their favorite happened to be. So now we pretty much have settled on a standard .355 groove dia. for everything that can possibly use that bore size. BUT....Colt was the last manufacturer to jump on that band wagon, so your barrel dimension depends on the manufacture date. (could be as late as 2002 IIRC)
Pressure..............
Go back and read the posts by MtGun44. What Bill describes is the development of the 38 Super used for USPSA Major Power Factor. At the time there was no "Open Division". Just as Col. Cooper envisioned, competition was being used to advance the art of pistol craft. Major power factor was based on 45ACP GI ball ammo (actually slightly less) at 180,000......bullet weight in grains multiplied by velocity. When Jim Clark introduced the "Pin Gun" the race was on! His original was essentially a muzzle weight to help dampen recoil and allow an extended sight radius.
Enter the 38 Super! Now we have eleven rounds a in the magazine instead of eight. But major PF is right at the top end of the available load data. OK, not really a serious problem....until somebody discovered that Clark's pin gun worked a bit better when the powder weight was a significant percentage of the bullet weight. So now we start looking at compensators to dampen recoil, lighter bullets and different powders to make the comp work better. Add electronic sights and we can really see how well our comps are working.
Bill says his 158 gr. bullet and HS7 load was 35,000 PSI, based on the Hodgden data. Definitely +P level pressure. Reduce the bullet weight to 135 and increase the powder charge to stay above the 180 PF requirement and what do you get?.......Nobody knew for sure..........but they did it anyway.
So Wilson and Nowlin started making "ramped" barrels. The feed ramp was part of the barrel instead of part of the frame. The result was a "fully supported chamber" which would help contain the pressure. Other manufacturers started making +P+ brass, another step in the right direction.
Somebody finally decided it might be a good idea to actually pressure test some of the popular 38 Super loads. The results were a bit sobering. Some of the loads generated 65,000+ PSI!!!
So, that's kind of a long winded way of saying.....Be VERY CAREFUL when choosing load data for your Colt. Most sources now separate their 38 Super data into standard loads and +P loads. Stick with standard loads from reliable sources in good quality brass and your Commander should last a long time.
Jerry