I'm about to undertake a .38 Super/9mm 1911 build. I've assembled .45 1911's before, but was wondering if there is anything special I should know about building a mid sized bore on the 1911 platform. Anything I should try to avoid?
I intend on using a Fusion Firearms slide on a Foster Industries receiver. Can anyone tell me the performance differance between a ramped and standard barrel (feeding reliability, I suppose) I suppose I would have to choose one barrel arrangement over the other as I guess the receivers are machined differently for each.  What's the concensus on Kart barrels, any good?
Thanks.

I would recommend adjustable sights so that you can tune point of aim for each caliber.

EGW's angle bore bushing is a great bushing and do speed up fitting to some extent.   Kart barrels are second to none in my, and many other folks's, opinion.

A super-extended ejector commonly used for 9mm can cause the longer .38 to hang a loaded round up when trying to eject it.  

If using an unramped barrel, be aware that the frame's feed ramp should be set up for the 9mm / 38 cartridge and not the .45.  Ramped barrels eliminate this consideration since they have their own ramp.

Ramped barrels also present a steeper feed ramp than an unramped configuration, which may cause nosedives with some mags.   Fixing this is mostly experimenting with different mags until you find one that runs well.  Tripp Cobramags are a good place to start.    However, getting a good barrel fit with a ramped barrel can be more challenging, especially when you are trying to achieve proper timing.   The Wilson-Nowlin ramp is easier to work with, IMO.

Be sure to order the proper caliber-specific parts such as firing pin, firing pin stop, ejector, extractor, etc.

I agree with what Ken said.  I am not a big fan of ramped barrels, but they do work.  Load your .38 Super/9mm reasonably, and you don't need the extra support that a ramped barrel supposedly provides.  I seriously doubt they add anything to feed reliability.

If you really want to rock and roll, consider the 9x23mm Winchester.  

Colt has made 9mm Gov't and Commander models for over a half century with non- ramped barrels.  In the case of the .38 Super, it is 80 years.  

Thanks for the replies guys.  I've secured a Fusion Firearms slide, and was considering using either the ramped or unramped Fusion barrel.  As far as the receiver goes, I'm going Foster Industries all the way.  I've used them before, and think they represent an excellent value, especially for a part that's going to get used quite a bit.  For the last 1911, I used all Caspian internals in the receiver, and everything fit together and functioned great.  I'm trying to decide if I want to go with Caspian internals again.  Perhaps I should keep Caspian lower internals in the Foster frame, and Fusion parts in the Fusion slide.   My mindset being to try an keep some uniformity between components.  Do you guys think there is any validity to this?   Thanks again.

yu cant go wrong with caspian and fusion parts.......quality stuff........I prefer ramped barrels when shooting 9mm para in the 1911 platform........all the high end 9mm 1911's sport ramped barrels and there is a reason for it........

I used a ramped Nowlin barrel and had no issues with feeding after getting everything tuned.  Using the Wilson 10 rd 9mm mags.  It seems like I'm shooting something ever so slightly hotter than a .22LR.  Good fun.  My frame was a Foster as well.  If you want to use a ramped barrel let them cut it for you.  There are 2 styles of ramped barrels if I remember correctly so pick the appropriate one.  My Foster had some buggered checkering and I definitely knew why it was a second.  I learned how to touch up checkering because of it.  

What I noticed is that the slide seems to run sluggish in my 9mm 1911.  I experimented extensively with different weight recoil springs while achieving reliability.  In order for it to run without hiccups the recoil spring cannot be sprung higher than 12 maybe 13 pounds (my gun and my setup  Yours might vary)..  I figured the 1911 was designed for .45 ACP and the slide is just a little too heavy in 9mm .  Thought of sending the slide to EGW to get some weight removed and thus helping with the sluggishness.  

No experience with 9mm 1911 so I thought I ask the brain trust on my minor complaint.  My 9mm 1911 is just an expensive fun toy gun so no big deal if it remains a little sluggish.

Edit:  I recommend adjustable sights as well.  The Novak rear adjustable sights need extra metal removed in front of the the dovetail (like a shelf) versus the standard Novak.  Something to consider depending on where you get your slide and if they cut the dovetails for it.  I found out the hard way and had to break out the files.  If you get the Bomar cut then no big whoop.

Ain't that the truth.  It took quite a bit of fine tuning to get that POS dovetailed into the slide!!!  Entire top end is complete, now I've just got to get a few minutes...hours...days, to get the lower together.  Thanks for all the help.
Oh, and I need to score a few 9mm 1911 mags as well.   Definitly not a cheap proposition getting this one together!!!