I have bought a lot of J & T /Double Star parts and kits both from shops and directly. I have always found them to work hard to do the best they can to get stuff out to you. Not only that, their products are top shelf, equal or better than anything out there. I have found no one who gives better service or does more for their customers. They can not control many things like parts from outside vendors, especially in this time of panic buying and parts shortages. But they always seem to try their best to work with you to get you what you want.
Orders can come much faster if the customer is willing to be flexible and modify their order to suit what is obtainable rather than have some "Dream Gun" that they have to have today. One can always add a rail or other accessory later. Get the gun...the rest will come. Parts supplies will catch up in time. Right now one only needs to be patient.