First Carbine build - Problem with buffer spring

[nekite]

I was finally able to get some time to install a LPK into my stripped lower and bring it together with the complete upper I got from Grant. To anyone unsure of of doing this yourself, don't be worried. It was very easy and took just under an hour.

I am having one problem, however. When I cycle with the charging handle i can hear the buffer retainer and buffer retainer spring come free and end up some place in the trigger area. The buffer spring is now released and smacks up against the rear of the hammer. It does do this everytime, but very close to that often. What could be going wrong?


Thanks
Brian

[Robb Jensen]

You don't have the receiver extension screwed into the lower enough. On some non Mil-Spec rec. extensions you have to cut a notch in them to allow the retaining pin to work.

[nekite]

Thanks for your reply. I was able to screw the receiver extension in a little more. Still have the same problem. Here is how far my receiver extension is screwed in. Any further and it would require notching. Should I do that?


http://theknowledgeworks.com/AR/RE.jpg

[Robb Jensen]

Thanks for your reply. I was able to screw the receiver extension in a little more. Still have the same problem. Here is how far my receiver extension is screwed in. Any further and it would require notching. Should I do that?


http://theknowledgeworks.com/AR/RE.jpg


You need to loosen the M4 castle nut as far as it will go. Then pull the receiver end plate to the nut, remove the rear takedown pin spring. Then thread the receiver extension on as far as it will go. It should bind up the buffer retaining pin. Then while continuing to hold down the buffer retaining pin......... loosen the receiver extension just enough to align it correctly with the lower receiver, install the takedown pin spring. Push the retaining plate up against the receiver, tighten down the stock nut and stake the retaining plate to the nut.

[Matt in AZ]

Thanks for your reply. I was able to screw the receiver extension in a little more. Still have the same problem. Here is how far my receiver extension is screwed in. Any further and it would require notching. Should I do that?


http://theknowledgeworks.com/AR/RE.jpg

Would you confirm for everybody reading this thread that you had the buffer retainer and buffer retainer spring installed when this functional failure occured? As I view the photo, those items appear to be absent.

[nekite]

Ok, I think I win the dumb*ss newbie award on this one. I read all assembly instructions as the entire retainer was the "retaining pin" not just the center part. So when I put on the receiver extension, I did it until it binded against the entire retainer, and then backed it out. Of course the retainer spring would then launch the retainer out as soon as tension from the buffer was removed. Finally just saw a picture of a completed lower and the reality smacked me hard in the face, I need to screw the extension in further, and that retains the retainer assembly. I guess that's what I get for never looking inside friends' rifles whenever I used them.

Thanks everyone for your help. Now I get to go shooting.

[Matt in AZ]

The only people who don't make mistakes are those who don't do anything.

Nice work on getting this issue resolved. Have fun and train well!

[nekite]

Thanks. And the requisite finished picture.


http://theknowledgeworks.com/AR/FinishedAR.jpg


Once my Troy rear BUIS gets here tomorrow, I'll finally get to go out and shoot.