Ned Christiansen's FallArrest Hammer and Safety Set Patent Pending Prevents hammer fall / firing in the event of sear or sear pin breakage
For over a hundred years, a shortcoming has existed in the safety system of the 1911 pistol: the thumb safety blocks the sear, but not the hammer. The sear keeps the hammer in the cocked position, and with the sear blocked by the thumb safety, the sear cannot be moved by the trigger to release the hammer. But the safety does not block the hammer; so, in the event of a sear or sear pin failure, the hammer may fall and fire the pistol even with the safety on.
The lug on the inside of the safety, that typically must be carefully fitted at the factory or by a gunsmith to properly prevent sear movement, seems to be 'in the way' of the hammer when the safety is in the on position. There is a semi-circular cut in the hammer to make space for this lug. However, the safety lug and this cut in the hammer are shaped so that in the event of a sear giving way, even with the safety on, the falling hammer can simply bump or cam the safety down and off, allowing the hammer to complete its travel and contact the firing pin. With the sear 'gone', the hammer would not stop on half-cock.
The FallArrest set features positive arresting geometry so that if the hammer should begin to fall with the safety on, it will be caught by the safety. The locking surfaces on the hammer and safety lug will engage each other fully and prevent the hammer from striking the firing pin. Refer to Figure 1, "standard configuration", and then note on Figure 2, the positive locking features of Fallarrest. The geometry of these surfaces gives a self-locking engagement in the event of a failure so that the falling hammer is stopped about 1/3 of the way down.
The FallArrest set is also useful where the safety in its 'on' position does not positively block the sear from moving. This could be caused by improperly fitting the safety or changing out the sear or hammer and not testing for it being properly blocked by the safety. In this scenario, an inadvertent pulling of the trigger with the safety on could drop the hammer and fire the pistol, even if it has a Series 80 or Schwartz firing pin block. The FallArrest set would block the hammer's fall.
The 1911 sear is more robust than it may appear. However, it is not unknown for the sear tip to break off or for the sear to crack elsewhere. It is not unknown for the sear pin to break. Should a sear pin break and 'walk' out of the pistol far enough to the right, the pressure from 25-plus pounds of hammer spring would simply push the sear out of the way, dropping the hammer, camming the safety out of the way. If the safety had a very stiff detent, this might slow the hammer fall enough that the pistol might not fire. But in my testing, they all fire.
The FallArrest set adds no parts. It is intended as a gunsmith-installed hammer and safety set. There is nothing additional to its installation, no further fitting beyond what it takes to install any hammer and any safety-- no modifications to anything. You would never know it's there except in one of the above scenarios. Given that a custom 1911 often needs a hammer and safety anyway, there is no down side to adding another layer of safety. And given the cost of a Fallarrest set, compared to what would be spent anyway on an aftermarket safety and hammer, the additional safety feature is essentially at "no cost". The Fallarrest set brings much more than this added level of safety to your next build. The safety features a large paddle that may be trimmed to a more abbreviated style if preferred. The paddle continues further to the rear than most giving a better feel, and unlike other safeties, features serrations on the paddle's bottom which gracefully wrap around and blend to the top serrations.
More still: both Fallarrest parts reflect signature mods I have been doing to every custom pistol for years. The tool steel hammer is lightened for more positive ignition by taking the face down further; that face has a high polish to help in smooth operation. All sharp edges are removed for no-stitches manipulation, and each hammer has been inspected and hand-finished by me. On the safety, first a question: What stops the downward stroke of a 1911 thumb safety? It is part of the safety lug, hitting the frame window. In the traditional configuration, the contact point on the frame is somewhere on the bottom rear of the frame's widow where the lug passes through as the safety is assembled into the pistol. The contact point on the safety, is, well, a point. After a certain amount of use this point will create a small deformation on the frame where contact is made; metal will be moved outward, proud of the frame side surface, and start to wipe the inside of the safety. It's usually only a visual problem but who wants it? However as the hard downward stop point migrates further down, it may cause a little irritating bounce-back when the safety is taken off. No biggie but on expensive guns, it's not asking too much to not have it.