I went to moon clips on the revolvers I regularly carry about 20 years ago. They're MUCH better than speed loaders.
They're quicker, handier to carry and the shells are held so you don't end up dropping them like when you try to unload into a speed loader.
And when you cut a cylinder for moon clips you don't lose any features. You can still single load (rim headspaces on the unmachined outer portion of the cylinder) or still use a speed loader if you'd like.
If your gun isn't cut for moonclips, someone like TK Customs will machine it for $125 to $150. I've been really happy with every one I've had done.
I do not own a 627, but have a 625. I get distinctly better accuracy using the .45 Auto Rimmed than using the .45 ACP in full-moon clips. Group size is about half the size with the AR brass. A friend who has a Model 25 had the same results when he fired his revolver from a Ransom Rest. My theory is that there is a much more consistent hammer strike with the AR brass. The ACP cases are a little loose in the clips and the clips themselves seem a little springy.
I agree. I have had the same results. Admitadely, when the half moon clips were invented it was for expediency + MOA was not really an issue in trench warfare.
I get decent accuracy with the full-moon clips but much better with .45 AR brass. I use the full-moon clips for informal steel plate matches and the accuracy is totally adequate. I use the AR brass loads when I hunt jack rabbits.
I have owned an 8-shot S&W 627 for years and have fired it a lot, including competition. Full moon clips have proven to be the way to go, for me, hands down. Federal brass has proven to be by far the smoothest at dropping into the cylinder.