I purchased a KHW M4A1 which had a problem with the bolt. When I contacted airsplat they were very helpful and told me what I needed to do to fix my problem and prevent it from happening again.
Their solution made the problem worse, however. I sent the gun back to them (with all the parts) and they told me their recommended modification voided the warranty and they would not fix the gun.
As if this was not bad enough they did not (nor ever did) return any of the other parts other than the nonfunctional gun. After man calls and emails I finally gave up after about I year, calling the purchase a total loss.
Monetary Loss: $400.