I bought one of their model O1091 in year 1999. so, far I had no problem on it. I am trying to make it more accurate & reliable following some advices from internet gun writers and from TFL members. I put single full lenght guide rod, put a red dot, put an ivory grip, polish well the feed ramp and throat. It was advised that if the trigger pull is between 4 to 4.5 then theres no need to adjust it to lower pound pull. I bought match bushing for it, but I had not seen any difference with its original barrel bushing so I put it back. I also file rounded the pointed magazine follower of the ChipMcCormick for the pointed second layer magazine follower is putting deep dent to my feed ramp, now that is corrected also and I can't see any hassle to it already. When I shop around, I have seen that the new McCormick mags has no pointed mag follower already.
The little problem I had seen is, loosening of the rear sight but it was fixed now. I dehorned of the sharp edges too.
I was satisfied of its performance for these past few years for it eats all the bullets I am feeding, hollow points from Hornady, Corbon, Firestar of PMC and our own local bullets hereon.
What I don't understand well now, is, what is this statement i.e "the 1991A1 series is sporting a NEW Rollmark" that was put in the Colt web site. When I bought my piece there is no word like this before. Does it mean the model I had or stock I had bought is included in the new rollmark or just this latest production of Y2K.
Anyway, I had no problem on it, so perhaps my colt is sporting a NEW Rollmark too.
Enjoy your M1991A1 my friend.
Thanks