Question about using the "wrong" lens

Ok so If you look at my sig you will se that I have a 250mW 650nm laser from lazerer.Now it came with an acrylic lens that was IMO a piece of shit. I wanted to replace it but I didn't have any 635-660nm glass lenses, so instead I took a 405-445nm lens I had laying around and put that on it instead. I am currently getting around 305mW out of it whereas with the acrylic I was getting around 265mW.

So the big question here is wether I am going to damage my laser by using a 405-445 lens on a 650nm laser. I'm assuming the issue here is that the AR coating is not optimized for 650nm so I could end up causing COD due to light reflecting back at the diode.
Am I worrying for nothing, does it even matter at these powers? All answers are greatly appreciated.

IMHO you are worrying for nothing. The coating is there to lower the losses. The reflected beam wont be focused, so it should be harmless.

thats ok but IIRC you are not supposed to use a red coated lens for a blue laser.....

The coating will not pass the light to the lens efficiently. This may mean that the energy gets reflected back to the diode (usually plano-aspheric, so only part of the beam will reflect back onto the facet), or it may mean that the coating absorbs too much energy which may result in your lens melting. I'm thinking your lens may be in danger if it is acrylic, but if it hasn't melted or degraded yet, it will probably be fine.