Hi , I am now thinking about a quad rail for my new Bushmaster 14.5"/1.5" AR. It came with a tri-rail-"gasblock" and tri rail "hand guard". I decided to get a Magpul handguard so I removed the tril-rail handguard to put the Magpul on. After an hour of fighting with not being able to get the Magpul on, I realized I had to get the tril-rail gasblock off to install the Magpul handguard. So now I took them all off and have the Mapgul carbine handguard on there, but I am thinking about getting a quadrail. So what would be the different of a drop in vs. free float? I guess I read that a drop in, would be easy to install and I could do that myself (just like installing the handguards) but the free-floats need to be installed professionally? But they're better because they free float the barrel? Also I was looking at all the different ones on Primary Arm's website... And they had a Daniel Defense one, but then they had a Daniel Defense one that's larger for including the front sight block... Now which one would I need? I have a front sight block ,so I would need the larger diameter one? Basically, I would like a Daniel Defense one, could someone show me which one I would want (For a Bushmaster carbine ) ... and installation tips/? or best left to professionals? Lastly, it has *crossed my mind* about the piston retrofit, Bushmaster has a gas piston retrofit kit... But i noticed it includes new handguards...and I saw a quad rail that referenced (for use with gas piston ars etc.) so would that mean if I got quad rail, then got agas piston ,I would need a different handguard/quadrail to take into account the gas piston retrofit kit? Sheesh this is confusing. Thanks to all for the help.