Ellis,
I haven't built a Commander length but I've built two in 5 inch.
The recoil impulse with the 180 gr seems to be very close to a 45 acp with 200 gr bullets. I don't think timing will be a problem. I use a reduced power 155 gr load in mine for IDPA with a 14# recoil spring but the 180 gr would require at least a 16# and might work with an 18#.
One of mine is a standard barrel and it is a little finicky about the OAL in the 40 cal. I have to seat them .010 longer than normal to prevent stovepipes while feeding (could be the feed lips on the metalform mags). By the way, your mag choice is pretty limited right now! A couple of us have used 10mm mags with no problems.
The other is a ramped barrel and it is not picky about length at all.
The 40 is a fun project in a 1911 but you really don't gain anything since the 40 mags are 8 rounders in a single stack. I just like things a little different from everybody else. You can get one more with 10mm mags. It really shines in a hi-cap like the STI frame.
Mikey
[This message has been edited by Mikey (edited February 09, 2000).]