A clear epoxy will work best.
I wouldn't use a 5 minute type, I'd go with something with a longer set up time. One hour works well.
The trick is getting a perfect mix. I use a powder scale to weigh each component even if it's a 50/50 mix.
Degrease the stud with a solvent like Acetone or 90% alcohol.
If the epoxy has a setup time longer then 5 minutes, I spend more time mixing to insure a perfect mixture that will cure harder.
If you keep the assembly warm it sets faster and harder. Note WARM, not hot. A hair dryer pointed at it will do fine, or just put it in a warm place.
Brownell's sell a perfect type as "Acra-Weld".
http://www.brownells.com/gunsmith-tools-supplies/stock-work-finishing/stock-bedding-adhesives/acra-weld-cartridges-prod20983.aspx
Also, a better brand of one hour epoxy from a hardware store is good, just make sure you get one that cures clear, not yellow like many do.
Anything you can do to help the epoxy to make a mechanical lock in the stock helps.
This can be as simple as drilling or Dremeling a few under cuts in the hole in the stock, and making notches or holes in the insert.
These will give the epoxy "locks" in the assembly so it's not just a matter of the insert being able to slip out. To come out the epoxy has to break off.
If you can buy an insert that passes all the way through the fore end and has a recessed nut in the barrel channel that type doesn't need epoxy since the nut holds it in place.
The fore end stud is the one under the most stress and is usually the one that pulls out.
When you push the insert in some epoxy will come up out of the hole.
To help prevent a mess, coat the stock around the hole with a coat of wax. Shoe polish wax or Johnson's Paste Wax works well. Apply a heavy coat and don't wipe it off. This will prevent any epoxy that gets on the outside from sticking.
Insert a wood or plastic plug in the insert's hole, and apply wax to the exposed part to prevent epoxy from sticking to the outside.
Wait until the excess epoxy is like a rubber then use a brass, aluminum or hard plastic "knife" to cut off the excess.
Let the epoxy cure the full 24 hours.