Not that it matters, but my M4 was doing this in burst mode. I was told the sear was replaced to fix it but I wasn’t there or involved.
Ok guys, my brother brought the 6920 over last night. Had just a min tolook at it. First thing I noticed was the HAMMER PIN was walking out, and had completely come out of one sidewall of the lower. This indeed caused hammer to drop when releasing the trigger every time.
We had only a few min but I removed hammer, pin, and hammer spring. The HAMMER PIN has two grooves in it. One groove is in the center of the pin. However, when you look at underside of hammer, (up into the slot on the underside of hammer), it appears as if there should be some type of part in the HAMMER to physically hold the pin via its center groove. However, there is nothing there. Simply an empty hammer. My brother did some more googling this am and came across a forum (not sure which forum), but he saw pics others had posted that shoe the Colt hammer should have some kind of “j-hook” type piece, up inside the hammer to engage the pins center groove. Apparently this “j-hook”, aka “j-spring” is shaped almost like a fish hook, and is held in via a small piece of copper or something? I can honestly say I’ve got no experience with this piece he is apparently missing. I’ve always thrwn out my stock oColt triggers. Its been years since I’ve even seen a factory Colt hammer save for lastnight. Just a note, wnen the walking hammer pin is pushed back into place, fcg functions normally, with no problems. Anyone got pics of this mystery piece? My bro did not copy the link where he found this info, and I’ve not found a Colt diagram that shows this part, as apparently most diagrams only show the HAMMER, meaning its actually considered part of the HAMMER. Thoughts? At work, having hard time typing on phone!
OK, problem understood.
A hammer lacking the J-spring does not have anything that keeps the hammer pin in place. Vibration causes it to walk out, the rifle doubles, then stops working at all.
Solution: new hammer. If this is a new rifle, you might get some help from Colt, and you might not. Colt is notorious for the worst customer service in the known universe. The good news is, they don’t have the attitude that HK has.
Hammers come with j-springs, j-springs are not separate parts.
Yes Pat, thx, and nice of you to stop in. Other than specialized armament, does anyone else have Colt parts? (Brownells is out of stock on Colt hammers)
If you absolutely have to have Colt, then SA or Colt are the places to go. It may be heresy to say so, but a lot of other makers will do.
The best solution, but one not easily done, is to find someone with a box of hammers, and to swap hammers in and out until you get a nice, clean trigger pull.
Given the panic extant, you might just have to grit your teeth and pay for a Colt, wherever you can find one.
Pat, one more thing. SA’s website notes many hammers, and I believe I’ve narrowed it down to two. One says “type 1”, the other says “type 2”. There are also f/a and semi/a but IIRC, only semi auto will work. If it matters, the hammer in my brother’s Colt has a “2” stamped on it. Does this perhaps denote a “type 2” hammer?
Type 1 is the old style, rounded top. Type II is the new, “notch at the top” meant to frustrate attempted bubba-smithing meant to create slam-fires.
Get a replacement like the one you have.
Yours, being an early Colt, would be a Type I.
Oh, and .155" pins, not those wretched .170" ones.
Triple-post, that’s what I get for adding before the system is done updating.
Pat, how do you seem to know my brother has an early style Colt? His is indeed a .170" 6920, but I don’t recall stating that to you. Perhaps I did, and do not recall. Mobile phone can cause these issues, as its tough to load pages and previous posts at times.
As stated, its a .170" large pin model 6920. I will look again to see which hammer he has.
Ooops, juggling too many forums, posts and threads.
Got it, a 6920. match the Type i or II, to the existing hammer, make sure you get a large pin, and problem solved.
I saw Ken at the show in Phoenix this weekend. They are swamped like everyone else. If it were me, I would replace it with a genuine Colt hammer. Place the order now and just wait for it to show up.
First issue is that its a Colt. 
Well it is a colt
I inspected a gun that did this a few weeks ago. I forget the make, wasn’t Colt. It hadn’t been shot much but was out of warranty. I demonstrated to the owner that it wasn’t actually doubling but shooting twice with each pull of the trigger. He said he was going to leave it as is. Left the range happy as a clam.
As good a reason as any to replace your fire control group with an SSA from Geissele Automatics.
Just sayin’…