I just finished an ar for a friend but can't quite fig'r out my last puzzle....... When I pull the cocking handle back (all the way) and let it go......the bolt won't go all the way forward again. If i depress the trigger a little while pullin' back on the handle it slides right back forward...... And if I only pull the cockin' handle back about half way (enough to seat the hammer back) and let it go, the bolt slides all the way forward fine. I took the upper and lower back apart and there is some wear of the factory finish on the upper angle of the hammer but none I can see on the bolt. However, it looks as if it might be coming in contact with the bottom of the rear nodule on the firing pin........ What to do, what to do ????? Any assistance would be greatly appreciated.......
Thank you.....
"...freedom without sacrifice is NOT Liberty."
'bonz

For starter, read the manual.

http://old.ar15.com/books/TM9-1005-319-23.pdf

Once you have gone threw the manual, then it's time to start checking your lower receiver build to confirm that everything is install correct.


After you have checked/tested the FCG, then it's time to check the hammer and firing pin.

On the hammer, it may be a modified m-16 with the auto tab ground off. If this is the case, you may need to round the top edge to be like that of the semi AR-15. Also, check the tail of the hammer for contact on the disconnector. If your hammer is binding at the top round, then the tail will bind too, due to the hammer sitting closer to the carrier than on a colt.

On the firing pin, check the diameter of the retaining ring.  It may be a M-16 firing pin, and with out the hooded carrier, the hammer may be catching the larger than semi, retaining ring.

And, for the sake of your friend, stop building up other peoples rifles until you full understand the AR system.  It's one thing to have a problem on your own rifle, but when you start having problems on others, they lose confidence in the rifle and You!!!!!

Dano~
I did read the "manual" last night, from cover to cover (with the exception of the usual military beurocratic BS and inserts) and found it quite refreshing. Took me back to my military days and playin' w/ the M16's........

I did not have time or the space to go through the sorted details which transpired previously...... however, save it to say that my friend has already spent over 200 bones on "gunsmiths" who as of this writing haven't had a friggin' clue........... that's why he came to me. Secondly, I very much appreciate the assistance you and others' on this site have given to me and the countless others who have asked. I too find it somewhat disturbing when there are those who wish to fiddle w/ things that they know little or nothing about !! That sir, was my reason for ASKING for assistance....... I have NOT ran into this situation before and need help. (the hammer is a square-back m16 hammer, milled for use in an ar...btw).
In addition, I do not know whether you meant the tone of your response to come across as sanctimonious as it did; as if I were a computer geek in Silicone Valley who had never seen, let alone, touch a gun before.......nevertheless...it seemed to be and was uncalled for....... If NOT, my sincere apologies..........
In any case, thank you again for your assistanc.....now, and possibly in the future as well..........

"...freedom without sacrifice is NOT Liberty."
'bonz

No worries!!!!!

As you stated, the carrier will seat when you slightly pull on the trigger.  On the stock trigger, the hammer is pulled down as you draw the trigger.  This leads me to believe that the hammer and trigger holes were drilled a little higher on the receiver than on a colt receiver.  The old colt standards are used to build the parts, so on the non-standard receiver, the parts are not correct.

The easy way to test is to pull the bolt and retest just the carrier for binding, then the firing pin and hammer.

Let us know what you find, and we can steer you in the correct direction to fix the rifle.


update:
I just mic'd the firing pin on one of my AR's it's .330 across the retaining flange, and the height that the hammer is above the top of the receiver when cocked and held by the trigger is .475 to the very top of the hammer(semi type). If it turns out that the firing pin is a m-16 type(larger retainer), you can insert it into a drill and spin file the retaining to reduce the diameter.  As for the hammer, it's tempered and will need to be roll ground to remove the metal.  Just make a mark at the desired height, then re-grind the round to the new height.

Hope this helps.

Dano~

I ran some basic tests on the lower and everything was fine......... that is until I removed the hammer and the carrier.......... the bottom of the carrier has a concave groove in the bottom on the outer rim where the hammer penetrates the carrier case to strike the firing pin.... However, the hammer is indeed an "ground" m16 takedown hammer. on the top (as viewed with the hammer cocked) there is a "v"-type notch where the corner would be (seems to be what's left of the auto-sear catch) and the outher corners are geometricly square. There were no wear marks on the carrier or the firing pin, per se, but it looked like the hammer's corners were binding in the concave carrier recess from the spring tension on the hammer. With the hammer out the bolt carrier moved through the upper like shit through a Christmas goose; and all the other parts (upper and lower) worked great. I took the hammer to the fine stone on the grinder and slowly (as to not compromise the hardness of the steel) took off the sharpness of the corners and slightly rounded the upper-most corner on the hammer (in the cocked position). Viola'.......... upon reassembly everything functions A-OK; as far as the "dry" run goes......  I have a homemade rifle vice which is weighted that I use to test-fire the guns I have worked on and that will be the next stop for the lil' black lower....... Will let y'all know how the "live" recordings go..... Thanx for all your assistance.....and if ya' need somethin' sometime....don't be shy....!!!
"...freedom without sacrifice is NOT Liberty."
'bonz

From your description, the hammer is NOT a ground M16 type. It's an AR hammer, and you've got an AR bolt carrier.  What it sounds like is that the the catch notch on the hammer is in fact catching the ridge on the firing pin as it goes forward.  The reason it doesn't happen when you hold the trigger back is that, in that situation, the hammer is being held back by the disconnector hook, which hold the hammer farthwer back that when it's resting on the sear.

Grind a few thousanths off the front of that notch on the hammer, or replace the firing pin with an M16 unit that has a smaller collar that won't catch the notch.  

Not trying to be ugly here, but I find it hard to understand why someone who doesn't understand AR15/M16 mechanics would start working on someone else's piece. Your own---sure. That's one way to learn, but not another guy's.  

No sweat.......... I understand how easy it is to criticize someone you don't know, or to pass a judgement without knowing all the details......
But, It is mine, he bought a new (numbered) version and decided a small trade would be in order to get the problem-child off his back.
I do appreciate all the help given on this and other posts and thank you all in advance for any other, somewhat mindless questions that may be asked in the future.

"...freedom without sacrifice is NOT Liberty."

'bonz

OK---I withdraw any critisism.  Playing with and learning from, your own weapons is an age old technique for figuring stuff out.  We've all done it. Welcome to the club

Just wish there'd been an internet to get help from when I was doing my "learning".