I have an old Van Horn carbine bbl in 45 Colt, and my buddy has a factory octagon bbl in 45 Colt (both Colt only). You can use the "Ruger and T/C" loads, which are actually pretty impressive. I don't think T/C has made a straight 45 Colt bbl in years. You can find them used on the forums (I did) if you shop around. They do come up from time to time. Also, most any of the custom barrel makers can make you one in just about any length or configuration you can think of.
I very much doubt you will EVER encounter any "balloon head" cases, unless you are a cartridge collector and scour the gun shows and internet classifieds looking for them. I know they always put that caveat in their articles to cover their butts, but it is a non-issue.
I've been loading 45 Colts for 20+ years. One of the greatest attributes to the cartridge is it's flexibility (with modern high pressure guns). I can load under the original cowboy pressure loads, "standard" cowboy loads, all the way up to 300 to 335 gr bullets to 1300+ fps. I have a modern Colt Anaconda in 45 Colt, a current production Winchester 92 in 45 Colt also. These will take the high pressure loads as well as the Contender and Encore.
You have to always be aware of what gun you're loading for, I do have some old cowboy guns that would turn into hand grenades if I shot a modern high pressure load out of them (Single Action Armies). I only load certain bullets into certain loads, so at a glance, I can tell if the round is a "cowboy" load, or a high pressure load. There's a big difference in appearance between a 250 gr round nose flat point, and a 300 to 335 gr wide flat nose bullet. All of my Colt loads are separated in clearly labeled boxes so there's no chance for errors.
