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).
