Before the trigger job...... fit the trigger.
Just file or mill the top and/or bottom of the trigger shoe until it fits and presto, right? So few are that easy. Everything turns into something else.
I almost universally find that the trigger bow is too narrow, whether I'm looking at the factory trigger or looking to replace same. Its inside dimension is less than the width of the mag chute, and/or the trigger track in the frame is narrower than it should be and/or offset to one side; maybe the track is wide enough but it's deep on one side and shallower on the other side than the thickness of the bow material.
Why it matters: Mags will rub on the bow given half a chance. Result, variable trigger pull or draggy motion / sticking to the rear and not returning forward. Also, mags not properly dropping free.
The relatively easy part, usually: re-form the trigger bow. In this we are lucky that most aftermarket triggers and many factory triggers (especially when the factory sources triggers from the same aftermarket suppliers) are made of, well, rather soft stuff. Shoes are 6061 aluminum, not as durable as 7075 but a lot cheaper (even on such a tiny part, if you're making a lot of them). The bows, I don't know the exact material but it's something that is soft and "dead", almost like copper wire. It has no toughness or springiness to it. Honestly, these materials are "good enough" since when the trigger is in the gun, it's well protected. Outside the gun... be careful. But this bow material makes them easy enough to re-form. The hard part of the easy part is, if it's too narrow at the back where we have two 90-degree bends, there is no choice but to start by getting this area wider. Various tools come out, one of which is the forming tool from Brownell's. I use it some times for part of the process but it usually is also not wide enough. Once the rear crossover area is wide enough, the whole bow has to be widened and that's where the material used on most trigger bows makes things a little easier. To a certain degree, you can get this done with fingertips. Of course at some point, you get it too wide and it drags. Make it narrower! Then it's too narrow so make it wider. When you get it "juuuuust right", at that point the bow may be a little wavy. I'll take a certain amount of that in return for a trigger that works but.... sometimes ya gotta address it.
As I say, this is the easy part.
The hard part is if the trigger track is too narrow or way offset. Pillaring files work for this. I have a tool I've made and a process for getting this done faster / easier / straighter but pillaring files work quite well and leave a really nice finish.
The one I'm on now, I'm fitting two triggers. Only after I got them both to my satisfaction, and started to dig into the action work, did I discover one bow was too dang long-- causing zero pre-travel. Note to self, next time check this before putting work into shaping, texturing, and lightening the shoe and bow. I could have dealt with this in a number of ways but after trying a few things and considering / rejecting a few other things, I just swapped out the bow. I have considerable work into the shoe and did not want to do that over if I could help it.
Ya know there are a lot of Colt parts that are actually pretty dang good (my impression is that Colt's MIM parts are better than anyone else's). Most of their triggers have been pretty crappy in terms of shapes, contours, material and fit of the shoe, but I have noticed over many years that the bows are made from real gun metal. I took the crappiest Colt take-off trigger in the discard box, one of those with the shoe injection-molded over the bow, and simply clipped-off the plastic. The remaining bow is some tough stuff-- and still needed re-forming, considerably more difficult than with the soft ones. After re-forming I checked it for where it stopped going forward in the frame and it was a perfect match with the alternate trigger. This was not the first time I've done this but it has been so long that I don't remember exactly what I did last time. This time I made a staking tool out of a chunk of .45-70 barrel and re-staked the shoe to the new bow. Next will be to put lightening holes into the new bow, double-check for protrusion into mag chute width, and-- done.
Pics-- a brand-new, unused trigger bow. Just clip off the junky shoe and it's there for the using!
Staking the bow in place. Old bow is easily bent with light finger pressure (even before lightening holes are drilled). Note the solid O/T stop that is integral with the trigger. Something I suggested to EGW in about 2003 and they ran with it, glad they did. There are other good ways out there to skin the "screws come loose" cat too but I like these. Remove metal until you have enough O/T and it stays that way.