[300winmag]

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.

[300winmag]

In this installment of Saturday Night Gun Pron, I learn more than I ever wanted to know about M4 telescoping stocks. As I've worked on my own (I once owned three) AR15s, and others, I've come up with extra parts. This is, I think, my current inventory of surplus stocks.

The most interesting is the middle stock on the left. It's an original CAR15 sliding stock from the early 1970s. It's plastic-coated aluminum, rather than all-plastic like sliding stocks are now. The bottom two stocks are by Magpul, the middle one on the right is a generic M4 that came with the Colt .22, and the two top stocks are A1 and A2 fixed stocks.

When I started swapping things around, I accidentally stepped into the minefield of "mil spec" vs "commercial" buffer tubes. Both have the same thread where they screw into the back of the lower receiver, but the "commercial" tubes have a wall thickness a few thousandths thicker than the "military", so a "military" stock won't fit over a "commercial" tube. I finally was clued in when I read the instructions that came with the Magpul ACS stock, which I used first on my nephew's rifle.

I finally decided to order a "military" stock tube from Brownell's so I'd know what I was working with. I got the Magpul CTR stock (lower left), along with a strange buffer tube that was totally unusable on an AR15. Back again to Brownell's to order just a "military" tube, and a matching lock ring, just to be safe.

I was happy, my AR15 was happy, and I put all the extra parts, including the unusable buffer tube, in a box where I knew I could find them if I needed something in the future.

Then the Sig 556 arrived. I looked at it, and realized there was nothing inside the buffer tube, it was there just so the sliding stock could slide along it. That got me to thinking about the weird buffer tube I had, so I went to the shelf where I put it for safekeeping, and the box was gone!

Last week, I got the Colt M4-22. Since the Magpul stock from my AR-15 fit the buffer tube properly, I knew it was a "military" one also. So I ordered a Magpul ACS stock for both the .22, and the "real" M-faux, since I would be building them to be as identical as possible.

That got me curious as to where my stash of stocks and buffer tubes went. I looked in my "safe" spot on the shelf, and the box was back again! And now I realized that the "unusable" funky buffer tube was a folding telescoping tube that could only be for the Sig 556 family. Sure enough, I did a bit of swapping, and wound up with this:

And when I pressed the latch on the left side of the adapter, it gave me this

I don't know what I did to wind up with the Sig folding buffer tube, but it works like a charm, even with the "wrong" style of stock on it.

I'm waiting for the rear sling adapter to use with the folder, but that's on its way, along with the bayonet lug and bayonet. At that point, my unplanned mods to the rifle should be over (I hope).