So all this talk about adding a buffer tube to the mp15-22 pistol got me thinking about adding a buffer tube to my rifle. As it happened, I had an extra post-ban Bushmaster carbine style buttstock. It is a fixed stock with a rifle length buffer tube (so even if you could adjust it, you'd have a buffer tube sticking out the end).

Long story short, I ended up sawing off the fake buffer tube at the point where the receiver extension starts to taper down to the fake tube. The plastic ended up being thicker than I thought it would be so I had to hollow out the receiver extension so the threads of the buffer tube would fit.

I mounted an end plate (it hangs over a little, but I figure with a moe grip it won't be too noticeable).
In any case I used PC7 heavy duty epoxy around the threads of the tube (the tube fit very snug in the receiver extension to begin with).
I also added a carbine length buffer spring and buffer. I did this in the hopes that they will jiggle around a little with each shot to give a similar sound and feel as a real AR. Between the buffer and the BCG is an insert which does not move and sits flush with the receiver extension. The BCG will sit against this just as it did with the solid wall it used to and should function properly. But tests will be the final judge of that.

I know some of you will think me foolish for trying this. I can't argue with that. It was foolish, but I just had that itch. Overall I think it looks and feels better. I do plan on painting the lower OD green. Once the glue seams are finely sanded and the weather warms, I will paint it and his should hide most imperfections in the fitment.

Here are some pictures, cheers!

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Am I correct in thinking that you got the buffer tube to thread into the reciever and epxoied it in place? If so how much did you have to remove from your reciever for the buffer tube to fit?

nice job

Thanks! I had to use a 1" wood bit to remove the bulk of the receiver extension wall. The rest of the way was by using a curved file, lots of elbow grease. I'd say between the wood bit and the filing, I probably ended up removing 1 1/8 to 1 1/4" of material from the interior wall of the receiver extension. The threads would bite into the polymer, but I ended up abandoning the hope that the tube would thread its way in correctly. I filed the extension to the point where the tube just fit. mounting the end plate aided in making sure the buttstock stayed straight, the addition of the castle nut also helped.
By the way, the tube is commercial spec. I don't know if that really matters. The PC7 epoxy is incredibly strong too.

Wow. Can't wait to hear how it shoots and holds up over the next few months.

The ballsiest modification award goes to.............PainterlyShotgroup

Yeah, it could all end very badly I know. But I'm confident it will hold up, it's a .22

I'm sure it will be ok (knock knock). It looks like you did a fine job.

Thanks! I'll update on how it works. I don't think I'll be able to paint the lower until spring. So I'll reassemble it and test it out soon. I'm mainly concerned about the BCG being too sensitive to the mod and causing FTF,FTE Etc.
Hopefully it won't end in tears......

Sounds like the sbr bug is hitting hard this winter. Good job.

As long as the carrier sticks out of the back of the upper the same amount, I think you'll be fine.

Look at it this way, if it doesn't work or somehow brakes, you'll be the first to have a complete extra upper! You could have one scoped, and one with a dot/irons.

Sounds like I may have to start looking for a UBR.................

Forgive me, what is a UBR?

It's a Magpul stock that doesn't use a traditional buffer tube. It comes with a proprietary tube. The stock itself expands instead of adjusting on the tube.

i have an itch to fit an a2 butt stock to mine

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psalm 23:4 cause I'm armed

It can be done! You'd have to file off the little knob on the receiver end of the stock so it would fit flush. Or make a recess for it in the receiver extension.

Nice Job..

Also glad to know that the Original tube is Hollow and that square part is solid. I plan on doing a cheesy little mod that I will post up here but I wanted to know this info before attempting.



That would look cool too..

Doug,

You wasn't kidding was you! I bet your face was like when you took the saw to the tube and then when you drilled the hole you was like and then when you got the tube inserted you was like

Nice work!

Thanks! Anxious to reassemble and get it out shooting. The process was nerve racking believe me. there were definitely a few expletive moments. But it's like that line from "Reservoir Dogs" "Sometimes you just have to poop your pants, dive in and swim"

Cool man! Make sure to post it when you complete what you are going to do...

What part of California did you end up moving to, op?

That job hasn't come though yet. Fingers still crossed though. Why do you ask?

Ohhh, okay. Thought you were here already. Would be cool to shoot with a S&W forum member!

Oh definitely! I'll let you know. For a second there, I thought you were going to tell me what I did is illegal in CA. Haha

Okay I managed to sneak out quick and put around 150 rounds through the gun. I am happy to report that so far the gun works FLAWLESSLY!
No degrading of accuracy, no malfunctions of any kind. After I finished shooting I broke the gun down and inspected the bolt, inside of the upper and of course the lower. All normal. no indication of wearing or stresses.

The only difference that stood out to me, and I'm not sure if this is of any consequence, but it did seem that you felt the recoil differently. I didn't hear the "sproing" sound you get with a real AR from the buffer spring and tube, but there was a kind of knock or clunk as though the buffer does move slightly or something. Could also have to do with the hollow, open nature of the spacer the bolt rests against.

In any case I didn't mind the clunk, in fact I liked the feel of it. Made the gun seem more substantial. Might not be for everyone though.

I will continue to update if something bad happens.....

Hey Doug,

When you did this mod, did you actually thread the lower so the tube threads in? Or did you just get it close so it was a tight fit and then use the epoxy? I'm thinking the type of plastic the lower is made out of, would take threads nicely, may be no need to use epoxy?

At first I was naive and thought the threads on the tube would cut threads in the receiver extension, but I couldn't get it to work. It kept wiggling on me and would not go in straight. I didn't have any kind of tap, so I decided to get the fit as tight as I could and use the PC7 (strong stuff I must say). I am okay with it being glued in. I think if you have the right tools the plastic will take threads, I just wasn't able to do it with what I had.

Oh and I managed to get the lower painted OD green. I really like it. I'll post some pics soon...

These are bad quality pics but....

the boys

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Maybe I missed something, but why did you cut out the STOCK buffer tube only to re-install an AR15 Buffer tub??? Why not just leave well enough alone... Help me understand this... I like the fact it looks more like a real AR15, so I'm guessing that is the reason... Just a dumb city old boy... thanks.

^
Exactly! It feels more like one too. I'm sure as heck not going to put an AK stock on it....lol

Isn't it the pistol that you did this too?

NO. I want to be clear here. This always was and will remain a RIFLE. I cut the integral Buffer tube/buttstock off my rifle and replaced it with a real AR15 fixed carbine style buffer tube and buttstock.

I total read it wrong in the first post, ill learn to read slowly.

maybe you should attend "dereck zoolanders school for kids that cant read good... and stuff" hahaha just playin with ya

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psalm 23:4 cause I'm armed

Thanks, I'm on the same page now... and I like it... good job.

I would have thought the Same w the threading. Did you try to heat the female end up a Lil bit w like a Tile heater? I bet that would done it.

Also the Green lower looks Real good. great Job...

The thought crossed my mind, but I think it would take a lot of heat to make the polymer frame malleable and I feared in doing so I'd be running the risk of over heating and warping or distorting the receiver extension.

Thanks! I like the green as well. We'll see how long it stays on there though...

Did you get your cover installed yet?

Not yet, plan on doing it tonight. I also need to Pin my Stock.
I'll get er done tho.

& agreed w the possible warping, I was just thinking the surface would carve threads a Lil smoother if heated.

Looks good Doug!

Yeah you would have to spend some money on the tap to do the threads and I'm not sure what the size is. I'm sure it's googleable

Thanks Brett. While I didn't lay out a step by step procedure for what I did, I think the goal of this thread is to help anyone who's been curious about the possibility of doing this to know it can be done. Also, I'm sure with the right tools a much better job of this mod can be accomplished.

There is a chance your gun won't cycle properly now. Anything that will affect the recoil will often lead to stovepiped cases in a .22LR firearm. Unlike an AR a .22 is a blowback action which needs all the recoil assist the action has to get the bolt to cycle properly. They have a relatively narrow range of bolt movement that will successfully fire and cycle the next round in the chamber. It will either work, but differently maybe or it won't work at all and you will have a nice wall ornament. If you had left the spring and buffer out it likely would still work like stock.

Looks good, Nice job!

Mark

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It works like an off the shelf 15-22. I never had issues with the gun before I modified it and have had NO ISSUES with it since I modified it.
I was very aware of how movement of the bolt could lead to poor cycling and other malfunctions, which is why I put that insert in and made sure it sat flush with where the back of the bolt sits.
The insert that goes into the tube that the bolt rests against actually fits into the tube and has a lip that catches on the rim of the tube. It doesn't move at all so it provides a solid backstop for the bolt to rest against. The buffer and spring were more just for weight.
The gun functions 100% as it should.

Well it is good to know that you still have a functioning rifle.