I have a new M40. I've fired about 75 rounds through it. Following some advice on here, I decided to completely break it down to clean and lube the trigger assembly.
Using of one of the tutorials on here as a guide, it was a piece of cake. I removed all of the original lube with some Kleen Bore aerosol, let it dry and applied a coat of Eezox.
Re-assembly was a breeze as well. Once together, I noticed a very slight sound like something was loose when somewhat vigorously tilting the gun fore and aft. After taking a closer look, I noticed that the muzzle-end of the slide could be lifted away from (or pushed closer to) the polymer frame about .5 mm. So, I removed the slide assembly and found that the rails and entire inner steel frame could also be moved, rather easily, a tiny amount (< .25 mm, but visually noticeable). As far as I could tell, everything was where it needed to be (there are very few parts anyway) and everything functioned properly otherwise.
I have not yet fired the gun again. Is this something that I shoud be concerned about? Maybe I just didn't notice it before...
I appreciate any replies!