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MilSpec vs. Commercial Spec AR Buffer Tubes


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I get asked this a lot and I see people inquiring about this with enough frequency that a simple FAQ may help:


Real Steel MilSpec vs. Commercial Spec Buffer Tubes and Stocks:

Most real steel carbine stocks come in one of two sizes : MilSpec and Commercial Spec (aka Civilian Spec). Milspec was the standard for years, then one of the real steel companies (think it was Colt) started going after companies for making products to the spec they developed. As a result, some companies made slight alterations to the sizing and profile of their buffer tubes, thus the birth of the "Commercial Spec" buffer tube and stocks designed to fit it. A commercial spec buffer tube is typically longer and slightly wider than a Milspec buffer tube, and the commercial spec buffer tube often has a slanted end to the buffer tube (vs. the vertical end on the milspec buffer tubes). Eventually, the Milspec buffer tube was deemed non-proprietary, and everyone was allowed to make their buffer tubes to that spec, but there's still enough Commercial Spec tubes out there that some manufacturers like VLTOR and Magpul continue to make both MilSpec and Commercial Spec Stocks for them. Real gun users can use a Commercial Spec stock on their MilSpec buffer tubes ... but the stock will be loose due to the Milspec's tubes smaller diameter. Real gun users can NOT use a MilSpec stock on a Commercial Buffer tube because the commercial tube will be too wide, and even if they could fit it on, they can't collapse it down all the way on most stocks because of the Commercial Spec Tube's slanted back and length.

The Mil-Spec buffer tube is 1.148" in diameter while the Commercial buffer tube is 1.168" in diameter.


What does this mean for airsoft?:

AEGs - Most AEGs are based off the Tokyo Marui standard which is most similar to the MilSpec Standard. Airsoft Companies that follow this standard include G&P, Magpul, VFC, King Arms and many more (most actually). A TM Spec buffer tube is slightly smaller than MilSpec and has the same length and profile as the MilSpec (no slanted back). A Real Steel Commercial Spec Stock will feel ridiculously loose on an AEG Buffer Tube. A Real Steel MilSpec Stock may still feel a little loose on most AEG buffer tubes and even if your RS MilSpec Stock has a friction lock, like on the Magpul CTRs, it'll still be a tad loose. That said, I predominantly use MilSpec Stocks on my AEGs and I'm very happy with them. Whatever wobble/wiggle they have isn't really that noticeable to me.

Stocks designed specifically for AEGs sometimes have a slightly smaller inner diameter making them fit better on TM AEG Spec buffer tubes. However, most Airsoft stocks are MilSpec as they just copied the real steel counterpart which is why many of them are a little bit loose on our AEGs. The current generation of Magpul PTS Stocks allegedly have that slightly smaller diameter so they should fit better than the MilSpec tubes. Generally, for AEGs, I just suggest people get whatever spec (MilSpec or PTS Spec) they have access to. Just avoid Commercial Spec like the plague.

GBBs - GBBs are a little different. Many of them are much closer to Real Steel spec and that includes the buffer tube. Most buffer tubes on GBB ARs are MilSpec, so I would recommend going with MilSpec stocks over TM Spec stocks if you can.


A side note:

Magpul Stocks are pretty popular and one thing I have noticed is that Milspec and PTS Spec MOE stocks seem to have a smaller inner diameter than their CTR counterparts, so you may see even less looseness when those are used. (The MOE stocks were developed as an economical substitute to the CTR Stocks, and the MOE Stocks are simplified as they no longer have the CTR's friction lock. In order to circumvent the looseness of the buffer tube/stock design, they made the MOE Stock's inner diameter smaller for a tighter fit.)


Where to find MilSpec vs Commercial Spec stocks for the different stock tubes?:

If you're in the USA, most real steel retailers such as BravoCompanyUSA.com, RainierArms.com and SKDTac.com (to name just three) sell MilSpec stocks. Remember, if you're dead set on buying a real steel stock, you want MILSPEC, NOT COMMERCIAL SPEC stocks for airsoft. If you have an AEG and want a Magpul stock I'd suggest the PTS stocks, as they'd have slightly better fitting than the Milspec stocks (for AEGs). If you have a GBB, a real steel MilSpec stock may be better but you can probably force a PTS Stock to work with little effort. If you don't live in the US, you probably have no choice but to go with PTS Stocks but they are excellent alternatives.


Any suggestions on how to fix the wobbliness of my airsoft stock?:

I frequently hear people using a strip of electrical tape or in extreme cases a strip of duct tape stuck directly on the buffer tube or on the inside of the stock to act as a spacer between stock and buffer tube. Personally, I'd probably go with putting the tape on the inside of the stock as you never see inside it and you're constantly exposing the buffer tube when you collapse and extend the stock.




Hope that helps. If there are any further questions ask away and I'll do my best to answer them (if I know the answer that is).

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Do you have any information on how compatible ICS buffer tubes are with MAGPUL stocks or any other brand for that matter? I personally came across a problem when trying to fit a different type of stock for my ICS M4 and I came to find that the (chinese clone) stock was to small in diameter to fit over the buffer tube.

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  • 1 month later...

I'm currently upgrading my ICS M4 with Magpul MOE stock, forend & pistol grip. The MOE stock is a tight fit on the buffer tube but will slide with a little effort. The upside of this is that the stock does not wobble, the downside being its a pain to adjust. I also had the same problem with a Dboys Vltor stock which was even tighter than the Magpul. As an aside the Magpul pistol grip needs material removing to fit the width of the ICS gearbox.

Hope this info is of some help.



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  • 3 months later...

Just to add the standard stocks on Systema PTWs are commercial spec and as such airsoft stocks will not fit without modification.

There are several kits to convert the tube to milspec, and they usually include the parts for fitting a Li-Po inside as well.

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  • 3 weeks later...
  • 7 months later...


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