Loco, as for the dirtiness you experienced with Bullseye, well, you're not alone. Most reloaders consider it to be about as dirty as can be. I do, too, and I fired off many a pound of it. In recent years I've tended to the more "modern" replacements that have come along, but just last December I ran off a few boxes of 230gr Rainiers with Bullseye for a felt-recoil test.
Yup, it's still dirty.
But most reloaders who use it think it's about the most accurate pistol powder there is, too. I think it's fair to say that's pretty true. While I'm no benchrest shooter-type, I don't find any .45ACP load to be more accurate than that which I get with Bullseye.
Now, I don't mean to be disputatious, but I also know that in my case, and in just about everyone else's I know, the 1911 platform is the easiest to shoot accurately of all centerfires. Even my wife, who dislikes guns and shooting, does her very best shooting with one. Even more convincingly, two of my clubmates who are extreme Glock-guys (and I mean really extreme) will grudgingly admit they shoot straighter farther with a decent 1911 than with their wondernines, and both actually own 1911s (stealthily) for that exact reason.
There isn't a better trigger in full-caliber pistoldom. If you've got a Colt Gold Cup National Match, as I believe you say you have, it should not only have a very-good to excellent trigger, it should also be very, very accurate. Yes, there are a few dogs out there, but not many. I had one in the '70s that was insanely accurate right out of the box, and I never shot a more accurate centerfire gun, with the exception of a Model 52 .38 Smith I once had and my friend's GCNM Midrange .38 wadcutter 1911.
If you're thinking it's the gun, then maybe it's in need of a good cleaning (sometimes the chambers get cruddy and a regular bore brush doesn't get it all), or maybe it's time to have a smith look at it.
But if it's the ammuntion, consider a couple of things-
Are your primers seated consistently and well? Primers seem to be near the top of any reloading problem list. They're important, so check on that.
Is the powder measure you're using good? Are the charges consistent? It's not as important, but it matters.
Are you seating the bullets and setting a nice taper crimp properly?
Those Winchesters are good bullets. Bullseye is the target powder of choice for many, many shooters (and is the civilian version of the powder the .45ACP cartridge was designed around). And lots of folks consider the Gold Cup to be way up there in accuracy, and ease of shooting accurately.
Something's amiss, so keep looking.
Meanwhile, I use Winchester WST (Super-Target), one of those modern replacements, and find it accurate but much cleaner than Bullseye.
Bill