Home / Custom Shop / LMT® Barrel Conversion
// SOT Custom Shop · LMT® MRP™ & MWS
LMT® MRP™ & MWS Barrel Conversion
Send us the barrel you want to run — an AR-15 barrel for the LMT® MRP™, an AR-10 barrel for the large-frame LMT® MWS, any length and any caliber — and it comes back converted to fit, inspected and recorded to the same standard as the barrels we sell.
- MRP™ $135 · MWS $175
- Any AR-15 or AR-10 barrel
- Any length or caliber
- 2–3 week turnaround
// How it works
Three steps
1 · Order online
Fill in the form below and check out — return shipping is calculated at checkout. We check that your barrel is a candidate and email you shipping instructions.
2 · Ship the barrel
When our email arrives, send the barrel — that is all we need; the form already has the model of the LMT® upper it will be paired with. Include the gas block, gas tube or muzzle device if you want them installed.
3 · Converted, inspected, returned
The LMT® barrel interface is machined by our LMT-dealer conversion partner. We inspect bore and crown, install and pin anything you ordered, record the barrel on our inspection record and ship it back. Plan on two to three weeks.
// Pricing
Per barrel
| Service | LMT® MRP™ | LMT® MWS |
|---|---|---|
| Barrel conversion | $135.00 | $175.00 |
| Barrels accepted | AR-15, any length or caliber | AR-10, any length or caliber |
| Install gas block | No charge | No charge |
| Install gas block with Rocksett® on the set screws | +$1.00 | +$1.00 |
| Dimple barrel for gas block set screws | +$5.00 | +$5.00 |
| Pin gas block | +$40.00 | +$40.00 |
| Install muzzle device | +$4.00 | +$4.00 |
| Muzzle device timing — neutral, right hand or left hand | No charge | No charge |
| Matching headspaced bolt (optional) | From $79.00 | $99.99 |
| Return shipping | Calculated at checkout | Calculated at checkout |
// Matching headspaced bolt
Add a bolt, headspaced to your barrel
Any conversion can come back with a matching bolt, headspaced in your barrel and recorded with it. Choose one in the request form.
| Bolt | Bolt face | Price |
|---|---|---|
| Microbest C158 MPI bolt kit, chrome (phosphate extractor) | 5.56 NATO / 6mm Max® bolt face | $79.00 |
| HM Defense HMB™ bolt, black nitride | 5.56 NATO / 6mm Max® bolt face | $135.00 |
| Young Manufacturing 5.56 M-16 bolt, black nitride | 5.56 NATO / 6mm Max® bolt face | $89.95 |
| Young Manufacturing 5.56 M-16 bolt, chrome | 5.56 NATO / 6mm Max® bolt face | $129.95 |
| Young Manufacturing 5.56 HMB™ bolt with cam pin, black nitride | 5.56 NATO / 6mm Max® bolt face | $99.95 |
| Young Manufacturing 5.56 HMB™ bolt with cam pin, chrome | 5.56 NATO / 6mm Max® bolt face | $149.95 |
| Young Manufacturing 6mm ARC HMB™ bolt, black nitride | 6mm ARC bolt face | $99.95 |
| Young Manufacturing 6mm ARC HMB™ bolt, chrome | 6mm ARC bolt face | $149.95 |
| Young Manufacturing 7.62×39 bolt, black nitride | 7.62×39 bolt face | $79.95 |
| Young Manufacturing 7.62×39 bolt, chrome | 7.62×39 bolt face | $129.95 |
| Young Manufacturing .308 bolt (Armalite pattern), black nitride | .308 large-frame bolt | $99.99 |
// Before you send it
Good to know
It is permanent. Once converted, the barrel can only be used on the LMT® platform it was converted for.
What we need. The barrel, and the model number of the LMT® upper it will be paired with — you do not send the upper. MWS conversions are for large-frame MWS uppers only. The service does not include a gas block or gas tube — send yours, and a muzzle device, if you want them installed.
Gas block and gas tube. Low-profile gas blocks give the most clearance inside the LMT® rail. For adjustable gas, a symmetric low-profile block such as RIFLESPEED or Superlative Arms fits; asymmetric designs can contact the inside of the rail. Your barrel sets the block diameter (.625″, .750″, .875″ or .936″) and the gas tube length. Most conversions use a standard bent gas tube; a RIFLESPEED block takes a straight tube.
Integral gas blocks welcome. Barrels with no commercial path onto the platform — such as the gas-block-integral HM Defense Monobloc® — are exactly what this service is for.
Where we can return it. We do not ship barrel assemblies to California, Connecticut, Delaware, the District of Columbia, Hawaii, Illinois, Maryland, Massachusetts, New Jersey, New York, Rhode Island or Washington, or to Denver, Colorado, or Cook County/Chicago, Illinois.
Your configuration. A barrel under 16″ on a rifle-configured firearm makes a short-barreled rifle. Since October 9, 2026, ATF no longer enforces NFA approval or registration for short-barreled rifles. That is an enforcement policy following the Jensen and Silencer Shop Foundation v. ATF rulings, not a change to the statute, and it could change. Taking an SBR across state lines still needs ATF approval on Form 5320.20, and state and local laws on short-barreled rifles still apply. The firearm’s configuration is the owner’s responsibility.
Warranty. We warrant the conversion and the fit. The barrel is modified from its original configuration, so any coverage from its maker is at their discretion.
// Conversion request
Tell us about your barrel
Fields marked * are required. This is a request, not an order — nothing is charged here.
LMT®, MRP™ and MWS® are marks of Lewis Machine & Tool Company. Second of Ten is not affiliated with or endorsed by LMT®. Monobloc® is a mark of HM Defense, LLC, used under license. Other product names are marks of their respective owners.