I have had some problems with that model in the past, but they are fast when you get them tuned up properly. The biggest problem is the cock goes too far into the pan and the blast coming out of the vent hole blows your flint edge off or rounds it off. To solve this You need to add some material to the cock where it rests on the lock plate when it is all the way down, it lifts the flint out of the way of the vent hole that way. Inspect your lock carefully when you get it, I used an L&R lock recently and quality control seems to be slipping a bit, crooked screws, tumbler wobble, frizzen fit is bad, etc. Also get a full set of spare internals as these locks are notorious for breaking parts until you get a good set in it.
This is a double I built years ago that uses the Durrs Egg locks. You can see on the left one that the flint is now up and away from the vent hole now. These locks now are very good and very fast, this gun has won "Top Gun" on the sporting clays range at Friendship many times.