If you going to be driving out FSB pins on AR's you'll need a sturdy bench where you can set up directly over the legs or you're going to have to do the work on the floor.
I have an 10 year old Gladiator maple top work bench that's still as sturdy as the day I bought it. They're not cheap, but they are buy once cry once items.
Shop tables and workbenches pop up on craigslist that usually just need a new table top and a Uhaul to move that might be worth looking into.