So about a week ago, i picked up a bunch of floodlight bulbs that are all slightly used but all work. However, two of them (Philips Duramax 50w R20s) have loose bases, which makes it very hard if not, almost impossible to use them. Now i'm wondering how i can fix them since they both look like they have a lot of life left in them. I thought about using some sort of silicone compound, but i fear the bulbs would get hot enough to burn it. Does anyone have any suggestions/ideas that might work? Thanks.

Maybe you can use some high temperature epoxy of other glue that is used in ovens or kilns

I've used Gorilla Glue in the past with reasonably successful results. You have to be sure not to apply too much (it expands quite a lot..!) and let it set for at least 24 hours.