Let me begin by saying that the twin powders(H110/W296)are my favorite for .44 Mag full loads.May I also add that during the powder drought,I was one happy camper when I could find a pound of 4227.
This being put behind me,I'll let you in my findings.4227 is,in handgun use,a very slow powder.Being tough to ignite,always use Magnum primers.
In fact,4227 is so slow that its optimum use is in large hulls.44 Mag and even .45 Colt are on the small side for max efficiency .And yes,even when using mag primers you might find some unburned kernels in the bore.Add to this that in the .44 Mag platform it'll deliver from 50 to 100fps less than my favorite twin powders.
The other side of the coin is I've never found that the unburnt kernels left in the barrel wouls hamper accuracy.This fact actually got me scratching my head as to why it wouldn't do so...but I've found out that I'm better leave this question unanswered(for my mental sanity!).
4227 burns colder than most other high intensity powder...means longer barrel life.
And as mentionned above,accuracy is definitly one of its strong points.
I wouldn't be mad if 4227 would be from now on the only powder I could use in my .44mag!