I'm starting to do more serious running to round out my fitness and I'd like to get an idea of what is doable. Getting older really sucks for the stamina especially when I've never done med-long distance running work regularly. Right now I'm running 16:40 for 2 miles. From the army PFT chart, its 74pts (37-41) but I don't know if army personnel regularly max out the scores because the grade is set very low. The upper body strength standards are easy and I can max them out for the 21age group. I'm also doing longer sprints to help with my 1mile goal of 7minutes, still working on the stamina to sprint 400m. My 300m time is 50-55s. Not sure if the topendsports link score chart sounds reasonable because 55s doesn't sound good. http://www.topendsports.com/testing/tests/300m-run.htm http://livehealthy.chron.com/average-time-male-run-300-meters-8110.html
Like ironwolf said, just go lay down the best time you can and use it as benchmark. Try to progressively improve on that and keep track of your new PRs. I imagine that you'll make some pretty fast progress if you're consistent with your training. I too am over 40 and don't run much anymore because I wasn't smart enough about my training when I was young and it took a toll, but I've always enjoyed it.
I heard that Malcolm Gladwell (the "Tipping Point") guy broke 5 minutes: http://www.runnersworld.com/newswire/malcolm-gladwell-runs-454-at-fifth-avenue-mile He is in his early 50s. But he was a very good runner as youth and collegiate athlete. So I guess that is *really* fast for a guy of that age.
I've known some really fast older runners, cyclists and triathletes. just get on a proper running plan rather than just running a few days a week randomly and you'll see some real improvements even at longer stuff. As long as you aren't a total slob, if you dedicated 6 months to marathon training and foliwed a real program you would probably really surprise yourself. I know you didnt say you are interested in marathons.
I've asked myself those same questions a lot the last few years and the fact is, for me at least, Ironwood hit the nail on the head. Not only that if you're a bigger guy like over 200lbs you can also throw all those norms and standards out the window because I literally never see enough people performing up to standards to prove they aren't just outliers. Most of those standards some author just pulled out of his ass to sell his article anyway.