This is a very useful post. Thank you for posting.
As a first time user, I found the process of replacing the trigger return spring almost impossible. First, you MUST have a vise or some sort or a partner help you. If you don't have a vise or partner, plan on hours of frustration. It is too hard to do it otherwise. It's like attempting to thread a needle with someone actively thwarting you. As one who is fairly handy, just save yourself the time and don't attempt it without this.
Second, the coffee stirrer trick is clever, but it was very difficult for me to find a suitably small coffee stirrer. All the ones I found were too big. I wound up using the plastic tube from a Bic ball point pen. Even that was a little too big, so I "solved" the problem by melting the plastic a little bit which helped it shrink/be shriveled enough to stay attached to the spring leg. A few weeks after I needed it, I did eventually find a stirrer of the right type.
Third, a warning. When I was attempting to muscle the TRS into the space, I tried to do so using various tools like pliers and punches. It is possible to scratch/chip the plastic frame. I managed to chip a small piece of plastic off the internal frame. It's not affecting operation, even after a hundreds of rounds, but I feel bad about it. Thus, I strongly caution against excessive force. I think most people should, in order, (1) buy the TRS custom pliers from HK Parts for $20; (2) pay a professional to do it (call it, $150) or (3) don't bother because you either really don't need to go from V1/V2/V3 to whatever or, if you do, you should just sell the gun you have, get the gun you want and pay the $200 in the trade. The way this "operation" makes the most sense if you really like tinkering with things and will view the hours spent as "fun". I thought the first two hours were fun, the last two hours frustrating.
