Description
The Luth-AR BS-15M is one of those parts you don't think much about until you need one, and when you do, this is the kind you want. It's a 6-position mil-spec carbine buffer tube built to standard dimensions, so it plays nice with the huge world of AR-15 stocks and lower parts already out there. Whether you're finishing a fresh build or swapping out a beat-up tube, this one keeps things simple and dependable.
What Sets the BS-15M Apart
Luth-AR machines this receiver extension from 6061-T6 aluminum and finishes it in a Type III hardcoat anodized black coating, which is the same tough treatment you'll find on quality mil-spec parts across the industry. The six positions give you a good range of adjustment for length of pull, so you can dial in a comfortable fit whether you're running body armor, a heavy coat, or just want the stock tucked in tight. At 7.25 inches long, it matches the standard carbine footprint that most collapsible stocks are cut for.
Fitting the Luth-AR Buffer Tube to Your Build
Since it's true mil-spec diameter, this tube accepts the wide majority of mil-spec collapsible buttstocks, and it pairs cleanly with Luth-AR's own MBA-3, MBA-4, and MBA-5 stocks if you're building around their lineup. Installation is the usual carbine tube routine: thread it into your lower, seat the buffer retainer and spring, slide your castle nut and end plate on, then stake it down and torque to spec. Keep in mind this is the tube by itself, so you'll want a buffer, buffer spring, castle nut, and end plate on hand to complete the assembly.
Made in America and priced to be an easy add to any parts order, the BS-15M is a smart pick for builders who want reliable fitment without overthinking it. It's the workhorse part that just does its job and gets out of the way, which is exactly what you want from a buffer tube.
Key Specifications
- Manufacturer: Luth-AR
- Model: Mil-Spec Buffer Tube
- Manufacturer Part Number: BS-15M
- UPC: 859819007133
- Product Type: Buffer Tube / Receiver Extension
- Fitment: AR-15, Mil-Spec Diameter
- Positions: 6-Position
- Material: 6061-T6 Aluminum
- Finish: Type III Hardcoat Anodized Black
- Length: 7.25 in (7 1/4")
- Color: Black
- Country of Origin: Made in USA
What’s Included
- Luth-AR BS-15M 6-Position Mil-Spec Carbine Buffer Tube
Frequently Asked Questions
Does the BS-15M work with any mil-spec AR-15 stock?
Yes, it's cut to true mil-spec diameter, so it accepts the wide majority of mil-spec collapsible buttstocks on the market. It also pairs directly with Luth-AR's MBA-3, MBA-4, and MBA-5 stocks. Just make sure the stock you're using is mil-spec and not the slightly larger commercial diameter.
What's the difference between mil-spec and commercial buffer tubes?
Mil-spec tubes have a smaller outer diameter (around 1.148 inches) and a rolled-forward thread, while commercial tubes are slightly larger and cut differently. This BS-15M is the mil-spec version, which is the more common standard and gives you the biggest selection of compatible stocks. Match your stock to the tube diameter and you're good to go.
Do I need any other parts to install the Luth-AR buffer tube?
The BS-15M comes as the tube only, so you'll want a buffer, buffer spring, castle nut, and end plate to complete the assembly. If your lower is bare, a buffer retainer and detent spring round out what you need. Many builders grab a full carbine buffer kit alongside the tube to cover everything at once.
Is this the 6061 or 7075 aluminum version?
This BS-15M is machined from 6061-T6 aluminum with a hardcoat anodized black finish. Luth-AR does offer a separate 7075-T6 version under a different part number if you're after that alloy. For a standard AR-15 build, the 6061 tube handles the job just fine.







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