I've had mixed experiences with justbbguns. I had to threaten them with small claims court to get them to take back a faulty pistol. The replacement they sent (in the end) was new, but had the same fault. I fixed it with brown tape and lived with it because I couldn't be bothered to go through the same thing again.
They sold me two electric guns which *woefully* under performed the quoted figures on their site. Cheap rubbish.
I've bought some cheap shotguns from them which perform very well and I'm very happy with.
I ordered a recon gun. They accidentally sent *completely* the wrong gun. As it turned out to be a more expensive one I contacted them and just kept it - so not really a problem but hardly speaks to their competence.