View Full Version : new ar, have a question
bornhunter04
04-12-11, 03:51
So i have a DD 16" middy for an upper and a rock river complete lower, however the rear take-down pin, keeps working it's way loose while handling the rifle. I've picked up the rifle and had the upper 'open' up for me. So my questions is i understand this pin is made to come out, but shouldn't it take some pressure to push the pin free? Any idea's why it's doing this? This is my first ar so I definitely needing some advice on this phenomenon. Thanks in advance.
Also, wanted to add, that the fit between the lower and upper feels very tight, not like some ar's that I've fondled in the past, it seems as the they mate up very well.
Was the lower completely assembled from the factory?
Did anyone add anything or play with it?
It shouldn't be happening and I have to wonder if the detent that goes into the receiver on the right rear side via the endplate is missing.
So i have a DD 16" middy for an upper and a rock river complete lower, however the rear take-down pin, keeps working it's way loose while handling the rifle. I've picked up the rifle and had the upper 'open' up for me. So my questions is i understand this pin is made to come out, but shouldn't it take some pressure to push the pin free? Any idea's why it's doing this? This is my first ar so I definitely needing some advice on this phenomenon. Thanks in advance.
Also, wanted to add, that the fit between the lower and upper feels very tight, not like some ar's that I've fondled in the past, it seems as the they mate up very well.
bornhunter04
04-12-11, 04:01
no i assembled the lower, it came as a kit, so the lower hasn't been modified in anyway.
I'm not sure about a detent, I'll check it out when i get home.
Mr. Biggles
04-12-11, 04:02
Sounds like you're missing the rear takedown pin (Spring & Detent).
The spring compresses the rear takedown pin detent, which in turn keeps the rear takedown pin from popping out.
http://k.min.us/jjm45K.png
So i have a DD 16" middy for an upper and a rock river complete lower, however the rear take-down pin, keeps working it's way loose while handling the rifle. I've picked up the rifle and had the upper 'open' up for me. So my questions is i understand this pin is made to come out, but shouldn't it take some pressure to push the pin free? Any idea's why it's doing this? This is my first ar so I definitely needing some advice on this phenomenon. Thanks in advance.
Also, wanted to add, that the fit between the lower and upper feels very tight, not like some ar's that I've fondled in the past, it seems as the they mate up very well.
That's what I am thinking.
Sounds like you're missing the rear takedown pin (Spring & Detent).
The spring compresses the rear takedown pin detent, which in turn keeps the rear takedown pin from popping out.
http://k.min.us/jjm45K.png
So basically you had a stripped lower and you assembled it into a functional (?) one.
Do you have the proper tools? I.E. castle nut wrench, lower receiver vise block, vise, etc... Assuming you have a carbine, before you put the endplate and castle nut on there is a small hole in the rear on the right side. That hole should contain a small detent (pictured elsewhere) followed by a spring. It is held in place by the endplate which is held in place by the castle nut.
Once installed correctly you should have then staked the endplate. Can I assume that you did that?
no i assembled the lower, it came as a kit, so the lower hasn't been modified in anyway.
I'm not sure about a detent, I'll check it out when i get home.
TM 9-1005-319-23&P on page 25-3 has a good illustration of the rear takedown pin assembly.
no i assembled the lower...
I'm not sure about a detent
Huh?
Do you remember placing the detent and spring into the back of the lower before tightening the castle nut onto the rear plate?
That step should stand out because you need to make sure not to kink the detent spring when you're doing this.
jackblack73
04-12-11, 10:54
Yeah, I don't see how it's possible to assemble a lower and not know about the detent. Conclusion: he didn't install the detent.
By the way, there are two of these detent + spring units, one at the rear (pivot pin) and one at the front (takedown pin) of the lower receiver. The front installation of the pivot pin would be pretty memorable, because without the proper tool it's a PITA. If you did the front, you should have realized that one goes in the rear as well.
Yeah, I don't see how it's possible to assemble a lower and not know about the detent. Conclusion: he didn't install the detent.
That would be my guess... but I'd think the rear take down pin would come completely out of the lower.
+1 on Mr. biggles advice. usually takes some presure to make it come out. i usually use a plastic piece just to push it out. if its comming loose, id get rid of it and get a extended takedown pin. a lot easier to use.
Huh?
Do you remember placing the detent and spring into the back of the lower before tightening the castle nut onto the rear plate?
That step should stand out because you need to make sure not to kink the detent spring when you're doing this.
A) I think this is your problem for sure. I built my lower, and that was a particular pain in the ###. You would remember for sure. (I shot my spring around the garage, took an hour to find)
B) I kinked my spring but bent back into place installin DD QD plate, should i be worried??
B) I kinked my spring but bent back into place installin DD QD plate, should i be worried??
Does your pivot pin click when you open your rifle? If it does it shouldn't be a problem now. You should get a new one though, they are 75 cents.
By the way, there are two of these detent + spring units, one at the rear (pivot pin) and one at the front (takedown pin) of the lower receiver. The front installation of the pivot pin would be pretty memorable, because without the proper tool it's a PITA. If you did the front, you should have realized that one goes in the rear as well.
I used a flat head screw driver with a wide flat head to hold the front detent in place so I can insert the pin.
Saved the headache of shooting pins and made installation easier.
I finally shot a detent pin into the air on my last build. I found it though...
I only found it because I have spares from prior builds. If I DIDN'T have spares it would have been lost for sure.
I bought the Brownell's tool for my build. $15 for an item I'll use only a few times seemed indulgent...until I got the detent pin in on the second try with no chasing springs and pins across the shop floor and under the workbench.
Not to worry though, I was still able to experience that with the selector spring.
I kinked my spring installing a Noveske QD endplate...I have a spare, but just straightened it and used it again since the tension is fine and it works the same as before. I popped the buffer retainer pin into space, but found that.:D
I only found it because I have spares from prior builds. If I DIDN'T have spares it would have been lost for sure.
:p That sounds about right!
maxwell600
04-15-11, 07:58
Sounds like you're missing the rear takedown pin (Spring & Detent).
The spring compresses the rear takedown pin detent, which in turn keeps the rear takedown pin from popping out.
http://k.min.us/jjm45K.png
This is what I am thinking as well
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