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Posted: 12/22/2003 6:29:13 AM EDT
I have the guide that has all the parts and how to put them together that was on the web site. But I'm haveing a little trouble trying to figure out how to install the detent pins. The description that the guide has for them is that they are usually rounded on both sides. I got my upper and parts kit from J&T Dist. and I got to looking at the pins and they are flat on one end and come to a point on the other end. Should the flat end of the pin go towards the take down and the pivot pin or should the flat end go towards the springs when instralled. Can't tell by looking at the pictures which way they should go for sure. Are these pins allright to use. Will the pivot pin and takedown pin function properly when installed?
              Just another first time ar builder.
                 Wyo E.M.T.
Link Posted: 12/22/2003 6:33:03 AM EDT
You're good to go, Point to pin(s)
Link Posted: 12/22/2003 6:33:19 AM EDT
The pointed end goes towards the take-down pin, and the flat end torwards the spring.

When you install the front take-down spring/detent/pin, do the install with the receiver in a large plastic bag.  If you lose grip on the detent, it will be slung across the room to never be found again.
Link Posted: 12/22/2003 11:48:19 AM EDT
Let me throw in my little two cents...I bought a lower parts kit (my first AR)and it contained three detent pins as you describe.  I found that there was no way I could install the pivot and take down pin detents and their springs.  The springs would become coil-bound before the end of the pivot detent was below the edge of the hole (if that makes sense)or before the stock was fully installed.  Although it didn't seem right, the only way I could get the things together and working was to shorten the springs.  Then I bought another kit from the same company and had the same trouble.  Turns out they're giving me three selector detents and none for the pivot or takedown pins.  As you know the selector detent is pointed on one end, the others are rounded on both ends.  Make sure you have the right parts!
Link Posted: 12/22/2003 2:55:51 PM EDT
Thanks for the replys.
Crockett I have three pins all so. They are silver in color and come to a sharp point on one end and flat on the other. There smaller in size compared to the selector pin which has a bigger dia. and a flat base.
Do I need to get some different pins I really don't want mess around cutting springs. One already came bent. Called them and they said they would send me a new one.
Link Posted: 12/22/2003 3:17:09 PM EDT
Well, I've only built two, and the lower parts came from the same source, so I'm really not qualified to say if you need new pins or not.  My three were all identical in size, shape, color (black).  It sounds like you have two that are different than the selector detent and they may very well be intended to be used in the two other locations.  In fact, reading the posts before mine it sounds like those guys are saying yours will be OK.  Go for it!  Try putting it together without shortening any springs and see what happens.  If it's not right you'll know it, it'll be obvious.
Link Posted: 12/22/2003 3:25:09 PM EDT
I'll also add this last parts kit came with two pivot pins and no takedown pin, and a W-A-Y out of spec hammer that wasn't even close to fuctional.  I ordered the parts I needed to make the gun go together and work from Bushmaster.  I've decided that for parts like this I'm just going to stick with Bushmaster because it seems like a better bet than gypsy parts from the gun show!
(I didn't buy those problem kits from J&T Dist. by the way).
Link Posted: 12/22/2003 3:50:00 PM EDT
All the rest of the parts look fine. There are two pins the pivot and the takedown pin. Just one of the detent springs where trashed when I opened the bag that the lower parts came in. Suppose to be sending me another one to replace it. There are two other springs that where also in the bag one is about the same size as the detent springs just a hair shorter. The other spring is shorter and quit abit stiffer looking spring then the springs for the takedown pin and the pivot pin. Haven't quit figured out what that one is for. Maybe when I get started putting it together it will make more sense. Still waiting on my lower from Quantico.
Link Posted: 12/23/2003 5:52:33 AM EDT
what would be handy, and i'll do this next time i build a lower, would be pictures showing all of the springs and pins with the similar sized ones next to each other and labeled.  trying to figure that stuff out from line drawings is about impossible.
Link Posted: 12/23/2003 6:56:07 AM EDT
[Last Edit: 12/23/2003 8:31:02 AM EDT by threefiftynone]
[url]http://www.ar15.com/content/docs/assembly/lower/[/url]  for a good pic of all components involved, and some good instructions.

I've only built 4, so I'm no expert, but here's a tip on installing the pivot detents I stole from someone else on arfcom. Take yourself to the bedroom, turn all the lights on, and stick your upper body under the sheet.  put the spring in the hole, put the detent on it, push down with the pivot pin, and when compressed, push the takedown into place.  A tiny drop of oil on the pivot pin may help things go slick.

If you mess up and the detent goes flying, it's not going far, and it'll be easy to find.

Good luck.  Anymore Q's?

We're here.

Edited to change "takedown" to "pivot.  I told you I'm not an expert, right?  It does work.
Link Posted: 12/23/2003 5:21:12 PM EDT
That is the same thread that I used to compare all of my parts with. But for the life of me I still think they sent me an extra spring. I have a total of 4 springs. I know which ones go to the pivot pin and take down pin and I real sure the stiff one goes in for the selector switch but there is one more spring. It the same stiffness as the two springs for the pivot and take down pins but just a little bit shorter. So I'm not feally sure if the stiffer one goes in the pistol grip for the selector switch or if the other one does. Let me refraze that I have more then 4 springs I've compared the other ones and know where they go it just that one spring.
Link Posted: 12/23/2003 8:41:05 PM EDT
I think it's pretty common for an extra part or so to be in the parts kits, mine had a couple of extra springs in it, it's also not unusual for a small part to be missing, so always inventory the parts as soon as you can.

If I remember correctly, the selector spring is usually a little shorter than the takedown and pivot pin detent springs.

Link Posted: 12/23/2003 9:14:34 PM EDT
You say detent pins, I take it you mean the take-down and pivot pin detents?

The take-down pin is no big deal, but let me give you a tip for the pivot pin install. Go down to Home Depot and buy a piece of 1/4" aluminum rod stock (like a dowel). The holes in the lower for the pivot pin are nominally 1/4" but I found that you'll need to sand the rod a tad so it will move easily in the pin lugs. After you sand it finish with a little steel wool so it will be nice and smooth. Find a drill bit just a tad bigger than the detent and drill a hole through the rod maybe 1/8" or a little more from the end. Stick this through the takedown pin lugs from the opposite side, feed the spring and detent through the hole you drilled in the rod and push it in with a small allen wrench or whatever. Then, ease the rod back so the hole moves off the detent. Now, all you have to do is put your pivot pin up against the rod and feed it through, and the detent will pop into the channel in the pivot pin. This tool costs a couple of bucks and will add years to your lifespan, believe me. Or you can spend fifteen bucks and order the tool from Brownells, etc.

The other thing I'd tell you is take a file and blunt the tip of the detent. Otherwise it will really dig into the little stops in the pivot/takedown pins and make those a bit hard to shift when you want to open the weapon or remove the upper. If you ever need to remove the pivot pin, a scratch awl works well to hold the detent down so you can move the pin out - but put a rag or something over the lower or have a spare spring and detent ready 'cause those suckers will launch for lunar orbit if you let them loose.

The detent for the takedown pin is really easy. Leave it for the very end, when you put the stock on. Screw in the buffer tube, situate the buffer tube detent (speaking of lunar orbit, don't forget about that detent if you ever have to remove the buffer tube!) and slide the stock on. Feed the detent and spring in then install the buttstock screws. No brainer.

Selector detent: flip the lower over, drop the detent and spring in the hole. Go ahead and drop the screw into the pistol grip, then use your screwdriver or allen wrench to hold it in place. Now, flip the grip over and put it on the lower and tighten in place. Easy.
I've built a bunch of ARs so feel free to ask whatever.

I've built a bunch of these, lost more pins and springs during the learning curve than I can count. Happy to help, just ask.
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