I have in fact been bitten by a lost takedown pin in the middle of a hunting trip.... I salvaged the trip with a bolt and nut I found in the barn that just happened to fit the hole fortunately....
So apparently this mod has been around a bit but I hadn't ever run across it. I just completed the mod and it took all of 10 minutes taking my time on a DPMS lower. I didn't take picture because I'm lazy and it's fairly straightforward but some pics can be found over at arfcom. I will say the effort was worth it given the cost.
Parts/tools needed:
4-40 tap ($3)
4-40 1/8" set screw - allen socket($0.27)
T-handle Tap wrench (harbor freight for cheap/I already have one)
wire snips
Steps:
1. break down the rear of the receiver to access the rear takedown detent hole. (basically remove your buffer tube castle nut, receiver plate and stock)
2. using a little lube/oil/whatever slowly tap the hole using the 4-40 tap. go slow and back of if it binds. tap about 1/8"
3. use compressed air or a brush to clean out debris.
4. test fit depth of tap using the set screw turned in flush with the receiver. tap deeper if necesssary.
5. if your takedown was already tight you may need to trim the spring slightly with the wire snips. Better to take off less than too much and test fit. Too tight and getting the pin out becomes nearly impossible.
6. replace pin, detent and spring in hole.
7. install set screw
Your finished!
Some people put some loctite on the set screw but it likely isn't necessary unless you aren't going to put a plate back on the rear of the receiver (.22 mods, etc). Some receivers come with this mod already tapped into them (Aero, some Spikes and a few others). I took a look at several lowers on my shelf and found that the spikes was already threaded but none of the other brands. So I went ahead and put in a takedown pin on that lower with the mod also.
All of the parts I found at my local Ace Hardware (Mr. C's on Precinct Line Rd). You have to look to find the right set screws as set screws are in several different drawers in different places on the loose parts isle. I used screws that had allen sockets instead of the slotted style. I bought 10 of them to just add to my parts pile for every AR down the road.
Hope some others get some mileage out of this one.
