Anyone know where I can find a 70-series Combat Commander slide? Google-fu shows that Colt doesn't sell just the slide direct. Apparently SAWLE no longer deals with 1911s. Brownells is backordered.

Alternatively, can a 80-series slide be used on a 70-series frame?

Looking for one for a project on my CCO.

I would prefer an actual Colt, but I'll check those two manufacturers.

If you took out the firing pin safety plunger on the 80 it should work. At least in theory. That is the only difference that I have seen between the two.

If Brownell's has it and lets you backorder, don't be afraid to do that.  I've done that on a few different Colt slides and they all ended up showing up at my door.  The last one I ordered was a stainless series 70 Gov't slide.  The prices seem to be going up on that stuff.  The sooner the better to get it ordered.  The only reason I wouldn't order through Brownell's is if you definitely have to have it within a couple of weeks.

The one's at Brownells have no pictures and generic descriptions. No idea if they're blue or stainless.

This one at Fusion looks GTG if I can't find a Colt. https://www.fusionfirearms.com/1911-slide-commander-gi-45-acp-carbon-sight-cuts-rear-cocking-serrations

I'll put up a WTB in the EE and see if I get any bites.

There is a part that automatically depresses the firing pin safety that you can install.  I have one lurking in my parts box, but have no idea what it is called.  It replaces the two parts that actuate the firing pin safety and remains in the up position so that as soon as the slide is in battery, the firing pin safety is automatically depressed without use of the trigger.  I don't even know where I came by it, but never bothered to use it.

It is everyone's right to pick what they want in firearms, but would be curious to know why OP wants a series 70 vs series 80, or why it even matters.  I don't find the trigger pull difference between the two to be all that much of a detriment, but that is just me, and like I said, it is OP's right to buy whatever he wants.

Because my frame is a series 70. It's a Colt Gunsite CCO. I'm looking for another slide to do some customization as well as experiment with some new technology.

That just proves whats I have long believed.  Everyone has a reason for whatever they do.  Usually, if asked, they will tell you what that reason is.   OP's reason makes sense to me (not that what makes sense to me matters anyhow though).

Another reason, although mostly aesthetic, I don't like the front cocking serrations on the Gunsite slide. Gives me a reason to get something a little different up top, maybe with some engraving and a Royal Blue finish.

I was going to have the slide milled for an RMR, but after looking at the competition class options, I'll just pick up a dedicated gun for that (M&P9L CORE). I still would like to find a Colt Combat Commander slide to dress up my CCO, tho.

Awesome! My EE WTB add allowed me to scoop up a NIB Colt Gunsite CCO slide, complete (no barrel). Perfect match. Plans are to send it of to fill in the front cocking serrations, engraving and a Royal Blue finish.