One of my M4s with over 11,000 rds trigger is kinda gritty when it resets. I've oiled the tigger/spring/disconnector/spring/pins,hammer/springs
to little avail.

The grittiness is appearently coming from the notch on the back of the hammer that comes in contact with the trigger when cocked. When I remove the hammer/spring the trigger is smooth as  silk, when i put the hammer back in the grittiness is back.
- Any suggestions?

Won't some simple polishing/sanding fix it then?  Does it really matter that the reset is gritty?

Have you tried pulling the entire FCG and cleaning? Chances are that you have grit in the trigger/diconnector pin, and this is what your feeling.  

You already identified the source of the gritty reset.  Now find yourself a small wood dowel that fits the contour of the hammer's reset hook.  Wrap the dowel with 3/4 of a turn of 320 wet/dry and gently polish away the machining marks on the inside of the reset hook.  Finish with 400 then 600.  Clean the parts completely and use a touch of moly on the bearing points.  
What could be easier than that?
-WhiteFox

Never heard of a Hammer's reset hook, But do see that the AR-15 uses a disconnector.  Can I just buy one of them hooks, and throw away the fancy disconnector that came with the rifle?



Wouldn't it just be easy to polish out the burs on the contact surfaces of the sears with a light stone, since that is the only contact between the hammer and the disconnector.  Also, if you just lightly polished out the contact sears, instead of mutli-sandpaper grade finishing of the parts and wearing/sanding threw the surface heat treating of the parts, you will not have to re-heat treat the contact surface.  Also, since his rifle has already self polished threw live fire, his disconnector/hammer  have already self polished which means that his trigger/pin is loaded with crap and is what he is feeling as the trigger is pulled up during re-set.

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WhiteFox, don't take this the wrong way since I see that you are new to the site, but in the trouble shooting area, we resolve problems, and not create new ones.  Granted that I had a little fun with your post, others would have shreded you apart.  My suggestion would be to sit back and spend a little more time learning the correct name of the parts, and the overall design/function of the weapon, including what parts are best polished, and left alone.

P.S. Guys, lets just let it go at this in regards to his post, and not nail him to the cross by playing point/counter point at WhiteFox’s expense.  

Thanks,
Dano

uhhhhhh.............TWEAK?

After that many rounds threw the rifle, we are beyond tweaking parts, were well into replacement of parts.  

When you have the trigger/pin out to clean them, take a look at the face of the trigger sear for a groove. If the hammer has done such damage to the sear, you will need to replace the trigger. Tweaking the trigger, such as just milling the grove out causes problem due to this shorting front of the trigger, which cases the hammer to be retain high on the trigger at set, and the hammer will bind on the firing pin as the carrier return forward on the cocking stroke.

P.S. Any time you polish out a trigger sear, you thin out the case hardening, and this accelerates the wear of the part.

[lolabove]

IronBalaclava,
As you can see Dano523 has quite a sense of humor.

I haven't answered because I'm not sure of the question. In those cases I usually wait for others to draw the information out. Dano's on the right track, he's on it.

Thanks Dano.
Think I solved it temporarily.

I pulled the parts and cleaned them.
Their was a bit of rust in the knotch behind the hammer that contacts the trigger-cleaned the rust out.

On the trigger sear engagement surface there was a slight burr/marks from regular use maybe about 1/30 of a mm. I VERY LIGHTLY smoothed it out evenly with very fine grain sand paper,oiled and put the parts together.

WOW.

The trigger pull and Reset is MUCH smoother.

However I think I'm in the market for a new trigger/hammer when time permits.

For instructive purposes:  There are 2 important surfaces on the hammer.  The main hammer hook is engaged by the trigger (primary sear).  That part probably will not cause any gritty feelings during reset.  The other surface is the hook half way up the back of the hammer.  That hook is caught by the disconnect, or secondary sear, when the gun cycles and trigger is held back.  Releasing the trigger causes the disconnect to rub against the hammer reset hook and any irregularities in the metal surfaces will be amplified and felt by your finger.  

Suggestion:  obtain a short length of .154 drill rod and cut 2 pieces about 4 inches long.  Remove trigger and hammer and mount them (minus springs) on the outside of the lower receiver, using the long drill rod as extended pins.  You will then see immediately which surface is the offending one as you let off the trigger.
-WhiteFox