so after reading some old threads on the hide about flush cupping an a2 stock, and really finding no definitive information, I decided to pull the trigger (on my drill, that is) and do it.
Here's what you get with a 1/2" drill bit and some JB weld. I used grovetec hardware with external threads and a hex head to drive in the cup.
How to:
1) mark location of cup's center with a sharpie. Mine is 1" in from the reciever end and 5/8" up from the bottom edge.
2)punch a divot there with an awl or sharp nail. I then used a round burr on a dremel to make a starting hole for a small drill bit.
3) use a small drill bit (I used 1/4") to make a pilot hole. Don't put a lot of pressure on it, as once it's through it will punch to the bottom of the foam filling.
4) now go back with a 1/2" bit and open the hole up. You need to go down about 1/2" of depth. I went a little too deep and had to fill the bottom of the hole up with JB weld. Luckily it didn't damage the skin on the other side of the stock, or i'd be installing another cup on the reverse side.
5) remove any burrs from around the hole with a small file, sandpaper, etc. Thread the hole with a 9/16"-18UNF-2B tap. I didn't have one handy so I made the cup cut it's own threads. It took a lot of elbow grease, the plastic shell is really too hard for that. After a while, I got it in.
6)I threaded it in & out a couple times to clear the threads, then took it out and mixed up JB weld. Apply some to the bottom & sides of the hole, including the threads. IF you put too much in, it will come up through the hex drive in the cup. Thread the cup back in, and use a swab to clean out any excess. Make sure it's not interfering with the channel inside the cup. Wipe off an excess that is on the top surface of the cup/stock.
7) after it sets up, you can go back and fix anything you missed. I chose to paint my stock, since it was scratched up before ever starting this process. I also cut the rear notch like on the KAC m110 stock, and inserted a KNS stud I had in my parts box). Rough it up with a scotch brite pad, degrease, then paint away.
end result:
Here's what you get with a 1/2" drill bit and some JB weld. I used grovetec hardware with external threads and a hex head to drive in the cup.
How to:
1) mark location of cup's center with a sharpie. Mine is 1" in from the reciever end and 5/8" up from the bottom edge.
2)punch a divot there with an awl or sharp nail. I then used a round burr on a dremel to make a starting hole for a small drill bit.
3) use a small drill bit (I used 1/4") to make a pilot hole. Don't put a lot of pressure on it, as once it's through it will punch to the bottom of the foam filling.
4) now go back with a 1/2" bit and open the hole up. You need to go down about 1/2" of depth. I went a little too deep and had to fill the bottom of the hole up with JB weld. Luckily it didn't damage the skin on the other side of the stock, or i'd be installing another cup on the reverse side.
5) remove any burrs from around the hole with a small file, sandpaper, etc. Thread the hole with a 9/16"-18UNF-2B tap. I didn't have one handy so I made the cup cut it's own threads. It took a lot of elbow grease, the plastic shell is really too hard for that. After a while, I got it in.
6)I threaded it in & out a couple times to clear the threads, then took it out and mixed up JB weld. Apply some to the bottom & sides of the hole, including the threads. IF you put too much in, it will come up through the hex drive in the cup. Thread the cup back in, and use a swab to clean out any excess. Make sure it's not interfering with the channel inside the cup. Wipe off an excess that is on the top surface of the cup/stock.
7) after it sets up, you can go back and fix anything you missed. I chose to paint my stock, since it was scratched up before ever starting this process. I also cut the rear notch like on the KAC m110 stock, and inserted a KNS stud I had in my parts box). Rough it up with a scotch brite pad, degrease, then paint away.
end result:
