AR Trigger Will Not Reset

[patio]

I just wrapped up an AR build and ran over to the range for a test firing. For the life of me, and about a half dozen rounds of stripping and testing, I can't figure out why the trigger will not reset.

After a shot the trigger should reset to:
http://patomalley.org/triggerissue/2.JPG

But mine stays like:
http://patomalley.org/triggerissue/1.JPG

Any thoughts? Thanks in advance.

[Fang]

Are both your springs in right? It looks like the hammer is hanging up on the disconnector--which of course it should until the trigger is released, just not permanently. If the trigger spring had one part of it sitting on top of the trigger, that could do it. What happens if you try to push the trigger forward?

Also, got any pictures of your build? :)

[patio]

Fang you are dead on. I can manually reset it by pushing it forward. I dug out the old hammer and swapped it out, worked like a charm.

Now the question is, whats the best/safe way to take the finish off that spot on the hammer. I don't think any real meat needs to come off, just the finish which seems to be providing more friction than is helpful in this case.

As for pictures see below. I have a 10.5" Noveske on order but I imagine they might have a lead time, or lost my order, who knows. Hoping to have it in hand by mid Oct so I can shoot it with clinotus at our "OMG it's been 2 years and we both got fat" reunion.

http://patomalley.org/sbrshots/SBR_Spikes_NES.jpg

More BIG pictures here: SBR Shots (http://patomalley.org/sbrshots/)

[Fang]

That is one mean-looking rifle. How are the nosebleeds?

For the disconnector, you could take some fine sandpaper (600-800 grit) and wrap it around the clip section of a cheap ball point pen cap and use that to lightly take off some of the finish. I'd be tempted to just stick the hammer and trigger in the lower with the pins and springs in place, put a dab of lapping compound, bore paste, or jeweler's rouge mixed with oil on the point where the disconnect meets the trigger, and (keeping a thumb on the hammer so that it doesn't release and bang up the lower) work the trigger back and forth so that the two parts lap into each other--that'd be guaranteed to get the trouble area. Just be sure to hose out the lower with cleaner to get all the abrasive crap out.

[harristactical]

The Hammer and other parts are case hardened, so too much filing off the surface could result in double fires or worse. Sandpaper is too brittle for this type of sanding and a file is too harsh. A sanding stone will work but I do not recommend any griding.

I had the same issue with my Armalite LPK. Too much material on the disconnector engagement portion of the Hammer. Swapped it out with a new Hammer and voila! Called Armalite and they are sending me a new Hammer.

[Miso Beno]

The Hammer and other parts are case hardened, so too much filing off the surface could result in double fires or worse. Sandpaper is too brittle for this type of sanding and a file is too harsh. A sanding stone will work but I do not recommend any griding.

I had the same issue with my Armalite LPK. Too much material on the disconnector engagement portion of the Hammer. Swapped it out with a new Hammer and voila! Called Armalite and they are sending me a new Hammer.

The case hardness brings up an interesting point. Stainless steel doesn't take hardening techniques very well and there have been several stainless steel LPKs that have appeared on the market. I wonder how well they hold up in the long run.

[harristactical]

You are correct, stainless steel as a whole does not take hardening well. There are a quite a few different types out there and each serve a purpose.

17-4, 400 series, etc take hardening very well but 300 does not. 300 has a lot more nickel which is great for corrosion resistance but not hardening. All based on the amount of alloy. I am not an expert but know that steels with more carbon and Fe+ tend to harden better. They also rust easier than the ones with more alloy.

It's a science in itself and that's why I learned to take apart and assemble my AR's. Replacement of parts after thousands of rounds.

[Miso Beno]

You are correct, stainless steel as a whole does not take hardening well. There are a quite a few different types out there and each serve a purpose.

17-4, 400 series, etc take hardening very well but 300 does not. 300 has a lot more nickel which is great for corrosion resistance but not hardening. All based on the amount of alloy. I am not an expert but know that steels with more carbon and Fe+ tend to harden better. They also rust easier than the ones with more alloy.

It's a science in itself and that's why I learned to take apart and assemble my AR's. Replacement of parts after thousands of rounds.

That's how the folks at Mega explained it to me so I'm gonna go with you're correct. The problem with the harder stainless steels is they're more likely to experience breakages due to their high brittleness. One happy medium for corrosion resistance, cleanness of breakage, strength, and hardness is to surface harden the steel and then use an electroless plating such as chrome or nickel to protect from rust. The plating also helps with surface lubricity and in theory will help with the trigger's "smoothness."

The problem with that method, as I understand it, is if the quality of the plating is poor (expired solution, poor surface preparation) you'll start to experience flaking, which will leave areas of unprotected steel.