I have found that magazines help too. Just like what you find in the magazine aisle at like WalMart n stuff.
They arent as specific as the Gun Digest, but with some scouring you can find magazines with an article here and ther that will be specific to a firearm or system.
I sometimes look for the ones about certain cartridges. I know i have one here some where that goes through lots of different gr. for 5.56 and 6.8 and chnging upper receivers on the AR to use both.
So you can sometimes find useful stuff that way too in addition to the newest tactical bling!