A good cleaning just might do it, but if not...
If there are any weak links with the 101's, seems to be the firing pins and hammer springs. I've had two 101's, and both had FTF problems, and always with the bottom barrel. A badly pitted firing pin can certainly be a cause, and better-than-factory aftermarket pins are available.
I've found that more often than not a weak hammer spring is the likely culprit. Fortunately, changing out the springs on a 101 is a very simple 20 minute job for anybody that knows which end of a hammer to swing. There's really no need to pay a smith to do this. I really like the Wolf "extra power" 101 springs, although I found them be a little too long for easy installation.
http://www.gunsprings.com/RifleShotgun/Winchester_RsNF.html#Win101I cut 2 coils off each spring with a Dremel cutting disk, which still leaves them considerably longer than Winchester factory springs and eases installation. This has proved to be an instant, long term fix for 101 FTF problems.
