# Will a mil-spec AR-15 stock fit a commercial buffer tube?

**Verdict: No**

No. A commercial tube is about 0.022 inches fatter, which is enough that a mil-spec stock will not slide on. The other direction fits but rattles.

The two tube types look identical on a shelf and are not. A mil-spec receiver extension measures roughly 1.148 inches across the body; a commercial one is roughly 1.170. That 0.022-inch gap is invisible by eye and decisive in practice.

It matters in both directions, differently. A mil-spec stock will not go onto a commercial tube — the bore is simply too small, and forcing it is how people crack a stock or gall a tube. A commercial stock will go onto a mil-spec tube, but it sits loose and rattles, because it is sized for something fatter.

- **Mil-spec tube diameter** — About 1.148 in
- **Commercial tube diameter** — About 1.170 in
- **Mil-spec stock on commercial tube** — Does not fit
- **Commercial stock on mil-spec tube** — Fits loosely, rattles
- **Telling them apart** — Commercial rear face is sloped; mil-spec is flat

To identify what you have without a caliper, look at the back end of the tube. A commercial extension has a sloped, angled rear face. A mil-spec one is flat. Stock makers label their products for one or the other, which is the simplest confirmation that the distinction is real rather than marketing.

> **Caution:** Do not force a mil-spec stock onto a commercial tube. It will bind partway and can damage both parts, and a stock that has been forced on is not reliably removable.

## Sources

- [Magpul MOE Carbine Stock — sold specifically as Mil-Spec](https://magpul.com/moe-carbine-stock-mil-spec.html)
- [Wing Tactical — commercial versus mil-spec buffer tube dimensions](https://www.wingtactical.com/blog/commercial-vs-milspec-buffer-tubes/)

## More on AR-platform parts

- [Are M-LOK and KeyMod accessories interchangeable?](https://www.tactgpt.app/answers/mlok-keymod-interchangeable.md)
- [Will an AR-15 upper fit an AR-10 lower?](https://www.tactgpt.app/answers/ar15-upper-on-ar10-lower.md)

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Last checked 2026-09-02. TactGPT can make mistakes. Always check important info for accuracy. The information it provides is intended for educational purposes only. It does not give legal advice; verify any laws cited. Always follow all applicable laws and safety guidelines.

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