Receiver Buffer Install
Special thanks to Zach G for providing this write-up!
This is my step by step guide for replacing the old plastic factory buffer in your SPAS 12 with one of the new, better polyurethane buffers found at spas-12.com This guide is a bit long winded, but I find it's better to be overly detailed than to have you trying to guess what to do next. If all goes smoothly, it may take you longer to read this guide than to install the new buffer in your gun.
Tools you will need: A new polyurethane buffer. This one is the new model cylinder type buffer. The old model buffers are cone shaped. This particular buffer is from the test batch and was made of blue polyurethane. Yours will be black polyurethane.
A pin punch or something like a nail to knock the receiver pins out. Make sure it will not damage the surface of your gun.
A rubber mallet. The best choice for knocking those pins out. Don't use a metal hammer unless you really have to as this may damage the gun.
Nickle with a piece of masking tape on one end. It's easy to get and does a good job of removing the stock screw. I used the tape to prevent scratches.
A pair of almost any kind of pliers, or just use your hand if you are strong enough.
Optional tools: Paper towels. Mostly just used for a nice place to park your gun parts, but also useful if you need to clean your gun. Q-tips, tooth picks and gun oil. Used for cleaning the remains of the old buffer in a later step. You may not even need these.
Step 1: Remove the Stock
Bring your SPAS 12 to a well lit area to work. Check to make sure your gun is not loaded. Having your gun cocked will make disassembly and reassemble slightly easier, but either way, the bolt must me in the closed position. First, fold up the folding stock. There is a large screw in the back of the pistol grip.
Insert your 5-cent disassembly tool and turn counter-clockwise with your pliers or hand.
After the first few rotations you can work the screw out quicker by hand. Be careful when you remove the screw, there is a small washer hiding between it and the pistol grip.
Carefully lift up and back on the stock to remove it. Put the stock, screw and washer in a safe place.
Step 2: Open the Receiver
Our next step is to remove the trigger group so that we can access the inside of the receiver.
Elevate the gun slightly. You can use a friends hand, a book or use a towel like I used. Just above the trigger are two pins. Place the pin punch in the dimple of the pin and give it a light tap. It should remove fairly easily. Both pins are identical and the grooves are symmetrical, so don't worry about keeping track of which direction they go.
Once the pins are out, the trigger group will practically fall out of the gun. If it doesn't give it a gentle tug. These two pins were the only thing keeping the trigger group in place.
Note the two channels in the picture: one just above the S of the safety and one directly above the trigger. These are the channels the pins went through. Each channel has a spring on each end that locks into the grooves on the side of the pins.
Step 3: Remove Original Buffer
If your gun is like mine, the cheap plastic factory buffer disintegrated ages ago. Now will be a convenient time to clean all of the remains out of your gun action and receiver. Note: the hammer can be locked back or CAREFULLY released foreword for cleaning and the magazine door (the metal piece sticking out to the right of the safety on the previous picture) can be raised and lowered.
This is the back of the receiver. The rectangle on the bottom is where the trigger group went. The larger hole in the center is where the screw holding the stock on went. The hole in the top is for anchoring the recoil buffer into place. That orangish booger is what's left of the old Nylon buffer from the factory.
And there it is. On the left is the largest piece remaining from the factory buffer. On the right is the new polyurethane buffer going into my brother's SPAS. Note: the blue color was only used during testing of the original batch of buffers. The production buffers are made of black polyurethane.
And there is the rest of the factory buffer. If you are seeing this in your gun then it's time for those q-tips and tooth picks. Clean out as much as you can.
Step 4: Install new Buffer
There, nice and clean. Now insert your new buffer. The "tail" of the buffer goes through the hole in the back and locks it into place. Remember to get a new style cylinder buffer for the cylinder hole or a older cone style buffer for the cone shaped holes. This gun is the newer cylinder style.
The new buffer will install with a small click. That's it. No final struggle, no fireworks. Here is the prototype buffer I installed into my brother's SPAS 12.
Look at the back of the receiver and you should be able to see it sticking out
Here is the black production buffer I installed into my SPAS 12. You should be seeing something similar in your gun. The scratches and gouges above and around the buffer were caused by shooting the gun without a buffer. When firing, the buffer stops the bolt from slamming into the back of the receiver. Without it, the bolt impacts the receiver causing these gouges. This gun was caught fairly early in the process and the dings are only superficial and don't hurt the gun any. If it were allowed to continue, the gouges will develop into cracks and ruin the gun.
Step 5: Reassembly
Time to get the trigger group back into place. Pull the hammer back until it locks into place. It would be a good idea to engage the quick deploy safety to keep it from accidentally releasing. The quick deploy safety is the flat one on the left side of the trigger group (it's behind the trigger guard in this picture). I have the trigger group almost perfectly lined up against the receiver. There are the two holes for the pins to go through and also a groove for the safety bar. I have these marked in red in the picture. Put the trigger group in closer to the location of the pistol grip (right side of this picture) and move it forward (to the left of the picture) until the safety lever (or safety button) falls into the groove.
I flipped the safety back so you can better see the groove. Just slide it into place and go to the next step. Now to get those pins back into place.
It's easier to start with the pin closest to the safety. First, look through the hole and make sure the trigger group and receiver are lined up. The two have some wiggle room and the last thing you want to do is try hammering a pin into the side of your trigger group. The first pin should go in easily.
Next, install the pin closest to the trigger. Make sure the trigger group and receiver are aligned and tap it into place.
This is where the back of the receiver meets the stock. The stock has a groove for accepting the back of the trigger guard.
Put that small washer on the screw and put it through the pistol grip and into the receiver and hand tighten it as far as it will go. It may help to keep the stock folded halfway open.
Get the screw in this far and finish tightening it with Thomas Jefferson.
Very gently tighten it with the pliers, or wrench. Keyword here is gently. You want it hand tightened. If you try to Hulk tighten it, you're going to break something. This is the last step, as long as your gun isn't missing any important parts, it should be shootable.
If you are afraid your buffer might fall out, you can see the buffer and confirm it is still there by looking down the gap behind the bolt using a flashlight. Don't worry, it's still there. The electric blue of my brother's prototype buffer made this easier to describe.
And there you have it. Your gun is is fixed and no longer collecting dust in the closet and is ready to shoot another day!