Very nicely done Win-Mag. I sure can’t tell the difference between your Colt .22 and the M-4. I’ve heard the Colt/Walther .22 was very well made, it sure looks the part.
Well made, yes. But I've also found out that key dimensions of the upper and lower are probably 2-3% undersized, compared to a real M4. There isn't a single pin or spring that will interchange with the real thing. I think that was done intentionally so someone couldn't add centerfire parts, and turn it into a "real" M4. But you can't tell the difference unless you're really up close and looking for it.
The buffer tube (even though it's empty), Picatinny rails, and front sight assembly are the exact dimensions of a real M4. That made it easy to change out sights, the stock, sling swivels, etc.
The pistol grip was totally different internally, so I just couldn't slap on a new Magpul grip without some work. It needed fitting to a slightly altered contour of the lower receiver. The holes at the top of the grip needed to be slotted so the cap screw that held the grip to the lower would line up. I also needed to add spacers to the screw so it wouldn't bind up the selector switch when I tightened it down. That represented about four hours of work on a file-and-try-again basis until everything worked properly. I hate the original GI pistol grip, so it was an effort well spent for me.
The "simple" aluminum trigger bow was even more work, because the dimensions were so different when I tried to install it. I had to removed about 1/8th inch of the back of the bow, reshape the holes, come up with a new mounting method, and repair the lower receiver where I snapped the bit off when I tried to install it without fully understanding the situation. I estimate I've spent about three days of trial-and-error before getting it to work. As with the stock pistol grip, that fold-down "winter trigger" has always annoyed me.
The way things are going, I'll probably take both the Colt and the Browning to the range at the same time for first fire. I hope to have the proper scope for the Browning early in the week. Meanwhile, I have minor cosmetic details to attend to on the "real" M-faux and the Colt .22.