Mystery of the walking AR trigger and hammer pins

[mythaeus]

I bought a "complete" AR15 lower from a LE who told me that he had it built by an LE Armorer. I could tell that it was hastily put together from some of the tool marks and the fact that the buffer tube wasn't properly installed.

Anyway, I finally got around to really use the lower a few weeks back and both the trigger and hammer pins came loose, locking up the firing group altogether. I thought that the pins may have been problematic, so I replaced them with 2 new pins I happen to have without removing the assembly. Took the gun out again, and still the pins came loose.

I did some quick searches and someone mentioned that if the hammer pin walks, then it's the J spring under the hammer. If the trigger pin walks, then the hammer spring leg didn't catch the notch of the pin. I inspected the lower again and when cocking the hammer back, I thought it was unusually easy. I pulled the hammer pin out and looked at the hammer. Well, guess what? The freaking genius of an armorer had the hammer spring on BACKWARD. Instead of having the coil facing down towards the receiver, it was facing up. The tension of the hammer was about 1/2 of what it should be, causing it to not push against the receiver's holes strong enough allowing for the hammer pin to walk loose and the spring's leg wasn't strong enough to hold the trigger pin in place.

Anyway, just in case anyone run across a similar issue, correct hammer spring orientation is one of the things to look at. The rest of the moral of the story, you can determine for yourself

Al

[/dev/null]

Al, Im really glad you know how to assemble these... I havent a friggin clue (although with some googling Im sure I can come up with documentation).

Remember the kit I bought from you last year? How long "should" that take to install - never having done it before? Im pretty adept mechanically, but any tips youve got would be appreciated.

Thanks

[mythaeus]

Al, Im really glad you know how to assemble these... I havent a friggin clue (although with some googling Im sure I can come up with documentation).

Remember the kit I bought from you last year? How long "should" that take to install - never having done it before? Im pretty adept mechanically, but any tips youve got would be appreciated.

Thanks

First time at it, I'd say 45 minutes to an hour for the lower. The upper will take a couple of hours or more. To build the entire rifle for the first time, it's a good idea to take your time and dedicate 1/2 a day or more to it.

There are plenty resources online, especially those Brownell's "How to build an AR" series. I'd watch over the entire series to get an idea: http://www.brownells.com/.aspx/lid=11004/learn/

Don't go crazy with the tools. You don't really need a lot of the tools recommended in the videos.

Here is a good reference, particularly the parts diagram:
http://www.ar15.com/content/index.html#guides

There are also many youtube videos too. You will have no problem with it.

Al

[autotech6506]

It really is easy to build a lower. first time I did it only took me 30 minutes. I didn't have a hammer so I used a 2 different size vise grips to press the pins in. I looked on youtube to get the trigger springs and everything in the right way.

[Noah_Zark]

In general, if a person doesn't know which end of a Crescent wrench goes on a bolt head or nut, that person should not be assembling ARs or doing any other gunsmithing.

Noah

[mythaeus]

In general, if a person doesn't know which end of a Crescent wrench goes on a bolt head or nut, that person should not be assembling ARs or doing any other gunsmithing.

Noah

Unfortunately, I think it's the people who know which end of a crescent wrench goes on a bolt head automatically assume that they can assemble ARs or do gunsmithing without being able/having to follow simple instructions.

Al

[-JD-]

Al, Im really glad you know how to assemble these... I havent a friggin clue (although with some googling Im sure I can come up with documentation).

Remember the kit I bought from you last year? How long "should" that take to install - never having done it before? Im pretty adept mechanically, but any tips youve got would be appreciated.

Thanks

I've got a full set of AR tools. You're welcome to borrow them, or come on down one day and we'll put it together.

[Asmodeus6]

Unfortunately, I think it's the people who know which end of a crescent wrench goes on a bolt head automatically assume that they can assemble ARs or do gunsmithing without being able/having to follow simple instructions.

Al

Actually I know which way a wrench goes... and I've found it to be comical how simple guns are in comparison to automotive related work. In fact, there are often times I'm looking at a question about "taking it to a gunsmith" over the stupidest shit I have ever seen. And then having 20 following posts consenting that is the "right move". The lack of mechanical ability among many gun owners is downright appalling. To hear about someone hacking up as simple of a job as a hammer spring... and then the end user not noticing it either...

Well, it's just sad.

And then it falls into the hands of someone like you Mythaeus and you catch it nearly immediately. Kinda comical.

[mythaeus]

Actually I know which way a wrench goes... and I've found it to be comical how simple guns are in comparison to automotive related work. In fact, there are often times I'm looking at a question about "taking it to a gunsmith" over the stupidest shit I have ever seen. And then having 20 following posts consenting that is the "right move". The lack of mechanical ability among many gun owners is downright appalling. To hear about someone hacking up as simple of a job as a hammer spring... and then the end user not noticing it either...

Well, it's just sad.

And then it falls into the hands of someone like you Mythaeus and you catch it nearly immediately. Kinda comical.

You know, it was almost embarrassing to admit that I didn't catch it quickly enough. I didn't think to inspect the installation completely and just figured that the pins were out of spec or the receiver was...thinking "it was built by an armorer". I definite didn't notice the significantly reduced tension on hammer right of the bat. Oh well, at least it wasn't intuitive and a good lesson.

Al

[Noah_Zark]

You know, it was almost embarrassing to admit that I didn't catch it quickly enough. I didn't think to inspect the installation completely and just figured that the pins were out of spec or the receiver was...thinking "it was built by an armorer". I definite didn't notice the significantly reduced tension on hammer right of the bat. Oh well, at least it wasn't intuitive and a good lesson.

The first time I assembled an M16A1 lower while at 2111 school at APG in early '73, I got the hammer spring backwards. The class was mixed Army and Marines, and this particular section was being taught by an Army staff sergeant. After the spring fiasco I had to listen to the doggie staff sergeant go on about not being able to teach jarheads anything. I never forgot how to install hammer springs after that.

"Built by an armorer" -- LOL! I wish I had $50 for every time I heard that at a gun shop or show. The most memorable was at Allegheny Trade in Duncansville. Mark showed me an M1A with a NM barrel on a preban Springfield commercial receiver that "was built by a Marine armorer at Quantico." So I asked to strip it down and checked a few points and saw that no Marine armorer had completed that weapon. Maybe a 2111 installed the barrel, but there were other things that Quantico armorers did for M1As that were missing from the particular weapon. Not saying Mark was prevaricating; he may have been simply parroting the story that was told to him by the seller. Once again, caveat emptor.

Noah