I will explain:
When you do either mod you need to do a few things in order to see if the frame is a good candidate for what you wish to accomplish. Here is how I do it so I know right away what can and can not be used for a conversion.
1) Get all your parts FIRST! You need to get the actual rail that you plan to use and outfit it with a sear pin and sear. Having ALL the parts BEFORE you start is key. You should have the body and all the mounting screws as well. You do not need the valve system yet,.. but its a plus.
2) Measure, Measure, Measure! Assemble your rail and body together to form a loose fit. This will give you a rough idea on how things are going to line up. You NEED the body installed to find the "sear rest limit point" (thats what I call it because I cant find an actual name for it) in later steps.
3) Check the possible frame for the front screw and rear screw hole lineup. This is the step where most problems later on come from. The "sear rest limit point" is DIRECTLY RELATED to these 2 holes. You should ALWAYS take yout measurements from these 2 as they MUST line up with all ADG spec parts to work with AGD markers. Working from the front of a frame or a trigger pin hole is not a wise idea. They dont hold the same tolerances (I will explain that some more in detail later)
4) What actuator will you use? This is the point where you check out how much "play" you have to do which mod. The MPA-3 ram (the one Cyberave68 sells) is 1" long (un-cut). So you would take the distance from where you would like to drill your front mount screw hole (the center), measure to the back of the frame you want to use, and find the "sear rest limit point". The you would SUBTRACT 1" for the MPA-3 ram, then SUBTRACT .125" for pre stroke travel (MPA-3 has a much higher force when the sear isnt resting agains the ram/piston. This number is not made up, taken from Clippards Home Page). Lastly,... you need to SUBTRACT the amount of space needed for a barb on the back of the MPA-3.
5) Draw lines. You need to mark out the REAR lines of where the MPA-3 falls. Do you have enough room to fit it in, or do you need to mill some material out? Is the actuator going to hit the trigger in the frame you chose? The width is not important right now, you only need to know if this small piece will fit. You always need to be installing the parts and re-fitting EVERYTHING as it would work when your done. Skipping these measurement steps can be the reason for a working or failing mod.
6) Check front mount screw hole proposed location for ASA/vertical grip mount space. In the event you use a frame that has a much larger trigger guard design such as the EGO or Angel, you may have to mill or shift your frame to the rear of the rail to leave enough space for the ASA/fore grip. You need about 0.666" of space betwen the center of the front mount screw hole and the front of your frame.
7) Check the depth of your actuator. You need to remember that the sear does come down into the trigger frame some when it moves, so plan that into your calculations. This is why you need the body mounted for measuring. With the body mounted, your sear will only move as far as it can,.. thus you should be able to measure the radius of your actuator and know if it sits low enough. The radius of an MPA-3 is 0.281". If you mount the MPA-3 horizontal (meaning that whatever plane your rail is at, the MPA-3 SHOULD be mounted parallel to it) then you are safe. The actuator should hit the center of your sear at the bottom. Its important to mount it this way because of the amount of force needed is far less to move the on/off pin than it would be as a higher contact point or at an angle facing down.
8) Cosmetics. Now that you have all the hard stuff out of the way, how do you want this frame to look? I say this last because most guys look at the way things will be when its done BEFORE they can really say "this whole design will work AND look good when Im done". For me, this is how you can really make a project expensive REALLY fast! Knowing what you have to work with before you do it is great. If you were using a pancake solenoid to do this mod and you find out you cant get the front fore grip you want to use in with the frame because the location you have to drill a hole for the front mount screw wont work with the "sear rest limit point" BEFORE you drill anything,.. is kinda nice.
Most of the guys that have done this kind of mod before already do these things (maybe in a different order) so they will know right away where Im comming from. Those of you that want to TRY your hand at it,... go for it! Its not like its hard,... you just cant rush anything you do. If you dont have all the tools (drill bits, a means to mill or cut things), parts, etc,... you need to hold off till you get them.
~ P8nt