Hi all, I was wondering how to get the buttstock off of a 1971 SP1 and put on a collapsable stock. I have the spanner wrench, but can't find the hole it fits into around the buffer tube, what am I missing?

At the back of the buttstock you will find 2 screws. An upper and a lower. Remove the upper. The buttstock will now slide off. The buffer tube is removed with a barrel wrench tool. Remember righty, tighty. Lefty, loosey.

First, unscrew the top screw at the rear of the butt stock. Then pull the stock straight back off the rear of the gun.  If it's sticky and won't come directly off, tap the butt inseveral places with a rubber mallet.  As you pull the butt stock off, watch out for the small spring at the lower right of the rear of the reciever. Makr sure you don't lose it.

When the stock is off, you'll have to unscrew the reciever extension (buffer) tube. The rear of the tube has two flats milled in that you can use a proper sized wrench on.  As the extension tube is unscrewed, the retaining plunger and spring at the bottom of the threaded hole will come free.  Once the tube is off, you can install your collapsible stock assembly, making sure that the spring and plunger assemblies that were freed by removing the old pieces are repositioned properly.

Why don't you try downloading the -23&P old.ar15.com/books and read the instructions (and see the pretty pictures).  It  has complete tool listings and torque values too.

I would also add that you need to hold the buttstock in position until you have the screw completely removed, and then pull it slowly straight back, taking care not to kink (or lose) the spring and detent. Make sure that you remember your buffer retaining pin when removing the receiver extension (the buffer tube). In every subsystem on this weapon, there are lots of little springs under pressure. They will fly all over place when you go past basic field stripping.

When you reassemble the whole thing with your new shorty tube, make sure that you do not overtigtenhold the CAR plate in position until you have the whole thing mostly tightened up and again make sure that you don't kink the spring. There are also two kinds of spanner wrench because the M4 has a different kind of system (dang, my armorer's school stuff is already leaving me and its only been a month). I forget what the second piece is called, but make sure that you have the buttstock aligned before you tighten it down (this is supposedly a two-person job, but I have done it on my own).

If you mess this up and screw up the spring, your rear takedown pin won't be retained and will fall out (so you have an easy check to make sure that you got things right).

Hacksaw