There's lots of good advice above, tips scattered here & there. Bed rail is typically hot rolled and the rough surface is from cooling in air as it comes off the rollers. It work-hardens easily when heated (as by drilling or sawing). Heating both sides to red before (and a bit outside of) the drilling area does work to draw down the temper, as mentioned. If 'burning' with a 60xx rod, DC and neg polarity on it seems to work best.
Things to note from previous mention about drilling: High pressure, low RPM, and a dab of coolant in general, esp if minimal tools/ergonomics are at hand, ... or working literally in your lap as some small jobs can go. Piloting with a 1/8" helps with thicker drill bits (> 3/8") due to the 'web' of a bit having to 'push' vs the cutting that the lips do. btw: Use bits 1/32" - 1/16" larger than the bolts to be used.
Metal cutting depends on proper 'feeds & speeds'. In the trade we rely on the chip to tell us if a drill/tool is cutting properly. An old rule of thumb is 500 rpm for 1/2" drill bit or milling cutter on steel with HSS. Go proportionally slower as tool diameter increases and higher when drilling smaller. (12-1500 rpm with that 1/8" & the right pressure.) Double the rpm for aluminum, or with carbide on steel in the drill press. Double again for CBD on aluminum.
A power drill does not know the right speed/rpm to work at, we have to learn the ropes as we go. Use extra pressure to slow the motor if/as needed and keep the tip wet. Chip quality will let you know you when hit that sweet spot. That said, carbide in a hand-held drill is often a tough call, as a bit of wobble can easily chip a drill's corners or snap it off. No prob on a DP even at the higher speeds carbide likes to work at.