Improve your trigger....for next to nothing

I've never been a proponent of spending money when you don't have to. Sure, I've wasted as much money on impulse or uninformed purchases as the next guy. For the question of the AR15 trigger, why spend for an upgraded mil-spec trigger when you can do the exact same upgrade at home with the trigger that is already bought and paid for. This will not turn your trigger into something it is not, but it will do one thing- improve the quality of your trigger pull and hopefully make it more consistent. It will take the gritty feel away by removing the very small grinding marks left after the manufacturing process. Just run your finger nail across the angled front face of the trigger. If it is not as smooth as glass, your trigger can be improved upon. You can also try putting the hammer and trigger together and "sliding them by" each other just like they do when assembled into your firearm. It is very subtle, but you'll notice that they try to grab each other instead of sliding smoothly. If done correctly, the end product will be much like an ALG Defense QMS Trigger or a Palmetto State Armory Polished Enhanced Trigger, just to name a couple. It will not affect the creep nor will it affect pull weight by any reasonable amount. It could affect your pull weight slightly, simply by reducing the friction between the hammer and and the trigger, but the main element affecting pull weight is the hammer spring and secondarily the trigger spring. Anyway, here is an easy DIY method for polishing the mating surfaces of your hammer and trigger that will turn your gritty mil-spec trigger into a consistent, smooth shooter.
If your firearm is already assembled- I am not going to cover disassembly/assembly. There are plenty of places on the www and youtube to get that info. Here goes.

Disclaimer: I am not a gunsmith, armorer, or a firearms expert. I'm a diesel mechanic/garage hacker. My method is based on and/or identical to methods I have learned about right here on the internet. I have tested the triggers I have polished and they work. The rest is up to you and you are responsible for any modifications you perform on your firearm. This process can be done incorrectly and affect the operation of your fire control group so do this at your own risk. 
If you are not experienced at handling tools and confident in your abilities, do no attempt this modification and either buy the correct parts (already polished) or consult your local gunsmith.
Also: There are some who say "Never polish or grind these surfaces because they are only surface hardened and you will remove the hardening, it will ruin your trigger and hammer"
I'm sorry but if the hardening is removed by simply polishing the surface then something is seriously wrong with your trigger to start with. 

Materials needed: Your fire control group. A triangular ceramic sharpening stone. A Dremel or similar tool with felt polishing tips. Preferably the pointed tips like in the picture as it is easier to polish the hammer spur area with the point. Metal polish- I use Flitz. I've seen some people use jeweler's rouge which will probably work to but it can be expensive and it is harder to find locally. Flitz can be had from most local hardware stores. And lastly-good lighting and a clean, comfortable work surface.

Step 1:
Polish top face of trigger surface. You don't actually have to polish this surface as it does not contact the hammer spur but why not do it for practice. It is a wide flat area that is very easy practice on. The key is to hold the ground surface to the stone as flat as you can with no rocking. The entire ground surface should be contacting the stone at all times when polishing. This will avoid the possibility of changing the geometry of the FCG.  Experiment with different holds/grips. The more comfortable grip you have, the more control you will have. I polish in circular motion. Stop polishing when the "grinding marks" are gone. It should really take a only a minute or two to achieve this.

Step 2: 
Polish the angled front face of the trigger. This is part that contacts the hammer spur, so be very careful when polishing. Again, I polish in a small circular motion and do experiment with your grip on the stone and trigger. This surface has a smaller area, so it is more difficult to hold flat but will practice you'll get it right. Again, it should only take a minute or two get the grinding marks out. 

Step 3: 
Polish the hammer spur. This is where the triangular stone will help you out. When I started doing these, I was using a rectangular stone (actually it was one from my Lansky knife sharpening system) but you can't get a rectangular stone fully engaged to this surface because the surface is "notched" into the hammer. One edge of the triangular stone will fit right into the notch. Again, experiment with your hold and make sure this very small surface area is contacting the stone completely. You'll have to use a back and forth motion instead of circular on this one.

Step 4: 
Perform final polish on trigger and hammer surfaces. Put a dab of Flitz on the top of the trigger and polish away. There is no particular method here. Just try to hold the polishing tip flat and avoid the sharp corner at the front of the trigger where the two ground surfaces meet. Do not monkey with this edge! Stay on the flat surfaces!
The point of the felt tip will go right into the hammer spur.

It is pretty easy to achieve a mirror finish in a relatively short amount of time.

Now try sliding the trigger and hammer surfaces "by" each other. You should notice a big difference in how they interact. If you don't, you did it wrong :-)

My high-tech studio lol.

Now take it out and shoot it.