Harrison Design ignition sets are manufactured from top grade tool steel to provide precise fit and reliable, consistent function under the most demanding conditions. Each part is wire EDM'd and CNC machined for a precise +/- .0005" tolerance, heat treated to Rc 53 - 56, then honed and mirror polished to give Extreme Service in your pistol. The hammers are slightly narrowed to avoid unwanted contact with the slide or ejector. They have deep serrations to help you keep the hammer under control and all exterior corners are CNC machine beveled to minimize snagging and abrasion. The slotted Commander hammer is a classic custom feature that just looks right on a finely crafted custom pistol. The sear is shaped to minimize excess material, reducing weight. The sear nose features a polished primary angle and breakaway angle. Fully polished surfaces mean smooth operation in the points of contact between the disconnector, sear and hammer. While I don't care to use the term "drop-in" and all that it implies, many folks use these parts that way with satisfactory results as contact surfaces are pre-prepped.
Now available with the "TR" True Radius sear!
The True Radius sear differs from my standard sear in that the sear nose primary contact surface is ground (and then polished) in a radius true with the sear pin hole, hence True Radius. Standard sears have the primary contact surface ground in a flat plane.
In operation, the TR sear keeps even contact with the hammer hooks, so the hammer keeps neutral engagement with the sear. Life span is expected to increase, the part works well even in frames that have less than ideal hammer & sear pin spacing and parallelism and is much easier for the novice user to fit and get good trigger pull results.
Again, I do not advertise my parts as drop-in. There are just too many variables in dimensions and tolerances between frames and the associated parts involved to really make that claim and it be true. You should be able to obtain a satisfactory trigger pull with these parts but any or all of these standard jobs that are involved in a 1911 trigger job are to be expected and must be dealt with satisfactorily. This includes checking &adjusting the parallelism of pin holes and their squareness to the frame, checking & adjusting the diameter of sear and hammer pins and their fit to those parts, checking and adjusting for even bearing contact on both hammer hooks with sear nose, checking and adjusting for adequate engagement in the depth of sear nose to hammer hooks, adjusting correct tension setting of sear spring leaves, checking for adequate take-up resulting in correct operation of captive half-cock notch and any adjustment necessary to ensure it’s correct operation, correct operation and adjustment of over travel stop, correct operation and re-fitting of thumb safety, correct operation and re-fitting of grip safety, correct operation and adjustment of any firing pin blocking safety system.