Upgrading AR buttstock...


April 11, 2010, 09:08 PM
I have a Bushmaster with collapsible buttstock and I am thinking of upgrading to the Magpul ACS buttstock shown here:


I will be doing the upgrade myself and have never taken off an AR stock before. Will I be able to use the Bushmaster buffer tube and recoil spring? Are there any other parts I will need?

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April 11, 2010, 09:37 PM
Is the tube on the Bushmaster from the factory, or was it built from misc. parts? If it's stock from the factory, you'll need a stock for a commercial size tube, not a milspec one. Other than that, it's just as simple as taking the old one off, and putting the new one on.

Here's the link for the same stock, but in commercial (http://www.midwayusa.com/viewProduct/?productNumber=657859). The only catch, is it's out of stock.

April 11, 2010, 09:41 PM
I started to answer this but seanie! said it exactly right.

April 11, 2010, 09:43 PM
OK, so the Bushmaster uses a commercial buffer tube I guess?

What about the Colt 6920? is that commercial or milspec?

April 11, 2010, 09:46 PM

April 11, 2010, 09:49 PM
This is probably a stupid question, but why would there be a different buffer tube for commercial versus military AR's? I don't understand why they would design either differently.

April 11, 2010, 10:28 PM
commerical one is cheaper to make. which means...hold for it...MORE PROFIT. Go Capitalism.

April 11, 2010, 10:39 PM
commerical one is cheaper to make. which means...hold for it...MORE PROFIT. Go Capitalism.

From looking at them, I dont see why it is cheaper to make.

April 11, 2010, 10:57 PM
The commercial tube is extruded aluminum. The milspec tube is forged aluminum. The commercial tube is cheaper, the milspec tube is stronger. There are also dimensional differences, owing to the manufacturing process. The differences are pretty small, but big enough that you need to get the right stock to fit on the tube.


April 11, 2010, 11:01 PM
Coronach got it right, its in the production process. Really no need to switch to one or the other. Just keep with what you got..unless you want to go really hardcore with a total milspec rifle, which is good, but not really necessary.

Gary G23
April 12, 2010, 07:51 AM
"From looking at them, I dont see why it is cheaper to make. "

They can buy 6061 aluminum alloy for one third the price of 7075T6. Since 6061 is only half as strong as 7075T6 they make it a little thicker so it doesn't break, until you drop the rifle anyway.

April 12, 2010, 09:32 AM
Thanks for the info.

Is the mil spec buffer tube really twice as strong as commercial?

Is it worthwhile to upgrade to a milspec tube for a SHTF rifle?

April 12, 2010, 10:07 AM
Nobody seems to have published test results on bending the tubes to the breaking point. Whether it's "twice as strong" is certainly open to question until hard numbers are actually known.

SHTF criteria are questionable, too. Training and skill sets are more important. While having a reliable rifle is important, having reliable skills in tactics and target acquisition will do more. Neither tube is designed to fail in common use, what could somebody be doing that would endanger the operability of the weapon rather than use an alternative? Moot point, any reply is just imagination gone wild, not reality.

Commercial and milspec tubes are not interchangeable, a fat tube won't fit the skinny hole in the other stock. It's recommended to match them and get the best fit, not beat two parts together. Save that kind of thinking for a SHTF situation.

April 12, 2010, 10:24 AM
To be fair, he did not say that the tube was twice as strong, just that the material in it is twice as strong. Since the tube with the weaker material is also thicker, it is not clear exactly what that translates into as far as the relative strengths of the final products.

I suspect that the milspec tube is stronger, but I don't have any data to support it, and I'm also pretty sure that it's not so much stronger that I'd worry about it enough to switch out a commercial tube that I already owned. That said, all of my ARs have milspec tubes.


April 12, 2010, 10:59 AM
Tirod, commercial-spec tubes fail fairly regularly in carbine courses and such. And the cost to upgrade is very small. The AR telestock is notoriously about the weakest buttstock put on any rifle, even with the mil-spec tube, so why make it even weaker with a commercial spec tube?

April 12, 2010, 11:02 AM
Also most milspec tubes should be of good quality while it's likely there's more variance with commercial tubes. Just looking at two recently a Bushmaster commercial tube appeared to be of better quality than a Del-Ton and both sliders fit better on the Bushy. However I'd suspect that both are better than the Chinese complete buttstocks you see for $35.

April 12, 2010, 11:04 AM
Listen to me from experience chief, if you are getting a Magpul ACS stock, you will need a MIL SPEC BUFFER TUBE. Magpul has not made the ACS for commercial buffer tubes yet, supposedly in the summertime they will release it.

April 12, 2010, 11:26 AM
I have decided to add the ACS stock to a Colt 6920, which has a mil spec buffer tube. I guess if I like it I will eventually add one to the Bushmaster also, and either wait til a commercial tube ACS version comes out, or just change the commercial tube to milspec.

April 12, 2010, 11:28 AM
Here's a mil-spec buffer tube for $20:


I have a couple of these, one in use with a Magpul MOE stock. They're good. (Not much to get excited about with a buffer tube.)

April 12, 2010, 12:12 PM
The ACS is a great stock, it locks into place and doesn't move one bit. Comfortable on the cheek and looks great, you will be happy with this upgrade.

April 12, 2010, 02:23 PM
If I swap out the buffer tube on my Bushmaster, will I be able to use the same buffer, recoil spring, castle nut, etc? or do any of those parts have to be changed out too?

April 12, 2010, 02:50 PM
As long as you're sticking with a carbine length buffer tube, you can reuse your existing buffer/spring/castle nut. "Etc." could include a lot of things, but apart from the buttstock itself, you should be able to reuse any parts on the new buffer tube setup. Castle nuts are cheap and I would suggest buying a spare, but the size is the same so you don't actually need to.

April 12, 2010, 04:11 PM
Mil-spec extension tubes in stock here;
As are mil-spec ACS stock in black;

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