I’ve own and modified 1911 govt and commanders, but never owned an officer size or officer frame/commander slide.

Well first I built this from frame up that’s new for me with 1911’s
2nd it’s my first officer size frame which posed a few issues and 3rd its a officer/commander switch barrel currently 9mm and 41AE! One if my favorites.

I had to do a lot of parts modification sanding, grinding , polishing, etc,
And technically it’s not finished yet , the slide won’t lock back on an empty mag nor can I engage the slide release it needs to go back apprx 1/8” more. Don’t know reason fir this. The Nighthawk “commander” one piece guide rod had to be ground down by apprx 1/4” to close the bushing, the 20lb spring is IMO under your much stress, etc. the 41AE barrel again commander length won’t fit in my colt combat commander slide but I believe it’s bc this 80 series slide was not the same size as the colt 40/10mm slides and the 70 series frame allowed me to not use the 80series extra space/safety parts. I even had to modify the sights to fit.
Here she is:

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Looks like a fun project OP.

Do you have a commander length spring plug in it? Also it loos like the spring tunnel on the slide maybe longer than needed.

Can you take all the slide parts out except the barrel and get it to lock open? If not just take the slide and not put it on the frame but sit it on top and slide it back and look to see if you are able to see where or what you run out of space with.

Things to look at, the spring tunnel, and the rails. Any one of those being long can stop it.

I fixed it , it was the barrel bushing supposedly ordered as commander length but it was too long I shorten it and polished , now all works just fine. I’m fitting a 2nd barrel in 41AE to it soon, I already can tell I have to file/sand the barrel sides to fit in the slide even though all commander parts.