KWA, KSC, WE, and good old Tokyo Mauri are great companies. HFC, UHC, KJW, KWC are more affordable brands.
However, good luck getting Glocks and to a lesser extent H&K from a shop in the U.S. since they have a lawsuit pending against Airsplat and other U.S. Retailers.
Besides for Airsplat (which I have had good luck with but others haven't) these are the common U.S. Retailers:
evike.com (mixed personal results from these guys)
airsoftatlanta.com
kapowwe.com
airsoftgi.com
trintyairsoft.com
airsoftextreme.com
No not harder on guns unless it is a Japanese gun that was designed to take the next lower level of gas. Anything that runs green gas is fine.
The silicone oil isn't hard, just a few drops at the top of the bottle every 5 mags or so.
Thanks for the info!
Do you have any forums or sites that you follow for reliable info?
IE- I did a Google search for "hop up adjustment." I came up with some, less than detailed, info on a couple sites and a YouTube vid. The vid gave the most info, but the guy in it called a mag a "clip" and whenever he gripped the gun his finger was inside the trigger guard.