Gunsmithing AR-15 Stripped Lower Assembly - What Gives?

[Apothus]

So I picked up a Spike's Tactical stripped lower, and ordered a Rock River Arms lower parts kit for it from Rainier Arms. It showed up in the mail today, so I ran home and started to put it together. Everything went together nice and smooth, up until I got to the front takedown pin/pivot pin. The pin is way too big in diameter, it will not fit in the two holes at the front of the receiver. Doesn't matter if I push from the right side or left side, it's too big. I tried the rear take down pin in the holes, and it slides in just fine, so the lower is in spec as near as I can tell. Any ideas on what might have happened?

Place a call to Rock River and ask them to send me a new pivot pin?

 

[Temp9]

I think the front and rear pins are the same diameter. Try the front pin in the rear hole and see if it fits. This will tell you if the front pin is out of spec or the front hole. Also, if you can get a caliper and measure the OD of both pins, that should tell you if/how much the pin is oversized.

 

[stockdoc]

Maybe somehow a Colt large front pin got in that lpk bag.

 

[Hole Punch]

To Apothus- I've thought of getting a Spikes lower, or a Seekins for a little project fun. But as I don't have a FFL, and the big name stores in my area won't sell just a lower (has to be a complete rifle), how or where do I get a lower? I can't order one. Haven't found a vendor yet that will send a lower to anyone other than an FFL.

 

[propeine]

To Apothus- I've thought of getting a Spikes lower, or a Seekins for a little project fun. But as I don't have a FFL, and the big name stores in my area won't sell just a lower (has to be a complete rifle), how or where do I get a lower? I can't order one. Haven't found a vendor yet that will send a lower to anyone other than an FFL.

That's probably because it would be a federal crime. You can order one from most anywhere and have it sent to a local FFL then go fill out your paperwork and pick it up. Luckily a few of our local gun shops carry them.

Or you can order an 80% Lower and finish the machining yourself. That doesn't require any paperwork but does require a drill press or mill.

 

[bptactical]

I don't recall RR ever producing a Colt style large pin. That being said both takedown pins should be a hair under .250 and the holes in the lower right at .250. Measure the takedown pins. If the front one is out of spec contact RR. They have decent customer service and have responded well in the past for me.

Take a good quality 1/4" drill bit(or if you have access to pin gauges a .250 pin) and use the shank as a gauge pin. It should be a slip fit through both sides of the lower.
If not you have choices to make, either contact Spikes or I use a dull .250 reamer to chase the pin bosses.
Don't use a drill to clean it up.
There is another possibility, you are hanging up on the takedown pin detent. First check the detent, make sure the end of it is rounded over nicely, sometimes they have a pretty steep bevel and can hang in the hole in the end of the takedown pin.
A lot of folks will try to install the pin with the slot for the detent aligned and it can make it a challenge. Turn the pin so the slot is not aligned with the detent, get it started and then just rotate the pin so the detent springs into place.

 

[Apothus]

Thank you for the replies. As far as where to get the receiver, my local shop had 1 sitting on the shelf so I was able to buy it from them.

I thought maybe I was hanging up on the detent, so I took the spring and detent out, and the pin won't even start the hole. The rear take down pin goes in both holes just fine though. I guess I will call RRA and ask nicely for a new pin.

 

[bptactical]

Or if a local shop has one in stock, shouldn't run you more than 3-4 bucks. Can you measure the pin you have now? If it is Colt big pin, should measure .315.
If so I will gladly swap you a normal sized pin.