Looking for opinions of which caliber to choose, and I can’t find any info comparing the two in a PCC. Im leaning more towards the 10mm but the pros of suppressing and the price of the .45 makes me reconsider.

If i go 10mm I will probably purchase a Vector. Ill keep you in mind though!

If 10mm is a little too enthusiastic for blowback operation, what about a .45 ACP? What are the issues with it?

I looked at turning a 308 Win. chambered Spanish Mauser (19116, small ring) into a 45 carbine w/ a kit from Rhineland arms, kinda like the DeLisle carbine but not suppressed and not SBR'd (I don't play in NFA land).  Decided not to do it due to performance issues....

From what I recall the "issue" with 45acp in a 16in. barrel is that you don't really gain anything over a 5" 1911 barrel... Real world numbers from BBTI show hardly any gains at all after 4" of barrel.  Shooting at 100 yards is interesting with a 9mm PCC, and turns into small scale artillery at 200 yards.  I'd expect the same from 45.

http://www.ballisticsbytheinch.com/45auto2.html

10mm on the other hand will get you a bullet of almost the same weight moving at nearly twice the velocity as from a hand gun.  

http://www.ballisticsbytheinch.com/10mm.html

If terminal performance doesn't really matter much to you as long as certain minimums are met then the 45 will be cheaper to shoot.

If you want the most powerful caliber then 10mm. If you want something quiet suppressed then 45acp.

I tried a PCC in .40s&w, then thought, this PCC has a 16" barrel and it's kinda heavy, I have an AK-47 that also has a 16" barrel weighs ever so slightly more and ammo is cheaper, wtf was I thinking? So my PCC went the way of the dodo bird. Won't be doing that again.

What mag options are there for 45 ACP?  I just can't do Glock.

OP, I was going that route until I discovered the Roni. I got one for the Glock 21 and the 17/22. It’s not for everyone, but man it’s fun. Uses my regular guns and mags.

At least personally, I consider a PCC with few exceptions to be intended to pair with a handgun.

Preferably not only using the same cartridge as ones preferred choice in handgun but the same magazines as well.

Therefore, in response to the OP's question of 45-ACP vs. 10mm.  My response would be to answer his question with a question, "Well, which one of those two are you carrying in your preferred handgun?" And the follow up being, can you get a setup that uses the same magazine as that preferred handgun of yours?

In my mind, an exception of course for a basic 9mm PCC, that is more a case of so many economical guns that use plentiful and economical ammunition.

To this end.  Don't be afraid to get creative.  My primary carry guns are either a full size Sprinfield XD 45-ACP or a more concealable Springfield XDS 45-ACP 3.3"  No lower that I could find was setup to use thise magazines much less both of them, but I was able to build my own custom adapter block for them that I bolted into a modified standard lower.  The adapter has two side plates that rotate at the front such that when they are rotated up into the mag-well the thinner XDS mags fit and when rotated down and forward the thicker XD mags fit including the big 25-round high capacity mags !!! This gives me cross compatibility with both my primary carry handguns mags and also high capacity mags as well.  Cutting and stacking metal sheets of appropriate thickness and drilling through them and the lowers side walls and using a through bolt with a teflon lock nut to hold everything together like a masterlock padlock type assembly works very well.  You will probably also need to modify the lower itself and the mag catch system.  It takes some work and creativity, but it can be done.

Edited to Add = Yes, I did have to do a double stage mag catch one horseshoe profile wedge to lock onto the XDS mags with a single independent wedge nested inside to lock onto the XD mags.  Double springs, independent of each other but a mag release cone that released both at the same time.  But most anyone else making a custom block to fit just one kind of pistol magazine isn't going to have to deal with that complexity.

For ammo cost, 45ACP has the 10mm beat.  Unless you reload....

Then there is the BB vs DI.  One thing I keep in mind, is the 45 DI CAN have a limited diet of 45 SUPER loads (per Rudy in another thread).  Eventually, I want to pick up a DI pistol length upper (11") and pair it with another Spartan 45 lower (I paired a Spartan w/ an Olympic Arms upper).

Long, long ago, before the PCC became "popular", I purchased one of the ORIGINAL Keltec Sub 40s.  It was their ORIGINAL pistol cal folding carbine.... it was CNC machined out of aluminum, unlike the newer Sub-2000.  The original was sold with having the option of changing grips to use different magazines (at the time, Smith & Wesson and Glock were the only available, IIRC).  I believed in having a carbine that could use the same magazine as a pistol.  This was way back.... early 2000s.

Fast forward to today, technology has changed..... the AWB is gone too.  We have dedicated magazine lowers and from what I see, Glock magazines are the king now.  MPA offers a 9mm using Glock, Ruger offers their PCC w/ a Glock mag well.  That AK 9mm is Glock mag compatible.  Just saying.