Have a 416 receiver set.  I used it for about 1.5 years before my gearbox inside broke, then i built a mk18 and stopped using the 416 body.  The pink stuff is just dust and wipes off, so its not permanant🤣
There is a small crack in the front of the magwell, but it does not affect performance at all. It cracked before i ever used it, during assembly, and after 1.5 years of use it never expanded.  If you have any questions or offers let me know!  Sms 0683221892- stu