Slight gun malfunction on 1911. Help? Advice?

When you say "a good size mark," did you compare it to one of your casings which fired on the first shot?

Light firing pin strikes, my first instinct would be to check whether or not the pistol is fully in battery when fired. Especially with reloads; it can close enough for the disconnector to allow firing, but if it is not fully in battery, it could interfere with the hammer fall.

The second thing I'd look at would be the mainspring itself; It may have weakened over time and needs to be replaced.

I recommend, if you are not an armorer or someone accustomed to replacing parts in firearms, that you take it to a gunsmith and ask his opinion. If it's your defensive pistol, you cannot afford to guess -- get it fixed properly and make sure it is 100 percent before you carry it again in its lifesaving role.

When was the last time you stripped the slide? On a 70 series pistol it's pretty easy to get the firing pin out for inspection. If the pistol has not be serviced in a long time there may be some congealed oil in the firing pin channel.

Did you rule out ammo? Reloads with bad primers...old ammo that's been exposed to oil... or wet may not always ignite.

Taking a 1911 apart to change springs is actually pretty easy. Tutorials abound. You could have a weak or broken spring...or a spring channel the is full of congealed oil.

One last thing... if the pistol is not returning to battery.. you may want to take a good look at the chamber... and consider changing out the recoil spring

So... try fresh ammo

Clean the gun and relubricate

Replace main spring and recoil spring if needed

Have you tried using different brand of bullets?