Is this BCG compatible with the Partisan Disruptor FRT?

Yes. The MPI Nickel Boron BCG has an M16 cut, which is required for reliable operation with the Partisan Disruptor FRT. The M16 profile carrier tail provides the geometry the Disruptor's reset lobe needs to function correctly.

What calibers does this BCG support?

This BCG is chambered for .223 Remington and 5.56 NATO and is compatible with all mil-spec AR-15 platforms in those calibers.

What is the advantage of nickel boron over standard phosphate finish?

Nickel boron provides a harder, slicker surface than phosphate. It reduces friction between the bolt and carrier, runs cleaner with less fouling buildup, and is significantly easier to clean. It also offers excellent corrosion resistance.

What is Carpenter 158 steel and why does it matter for the bolt?

Carpenter 158 is the MIL-SPEC steel specification for AR-15 bolts. It provides the correct balance of hardness, toughness, and fatigue resistance under the high-stress cycling of semi-automatic fire. It is the same standard used by military contractors.

What does magnetic particle inspected (MPI) mean?

Magnetic particle inspection is a non-destructive testing process that detects surface and near-surface cracks in ferromagnetic materials. Every MPI-tested bolt is individually inspected to confirm there are no stress fractures or defects before it ships. It is the industry gold standard for bolt quality verification.

The Takedown Tools

MPI Nickel Boron AR-15 BCG — M16 Cut | .223/5.56

Name: MPI Nickel Boron AR-15 Bolt Carrier Group — M16 Cut
Brand: MPI
SKU: MPI-NiB-BCG-M16-556
Price: 159.99 USD
Availability: InStock

$159.99

Quantity

American Made Guarantee

Ships From the USA

Supports American Business

Shipping & returns

Share shipping times, return policy, or product details here. You can also connect this to a product metafield with the dynamic source icon.

Why American-made

Share shipping times, return policy, or product details here. You can also connect this to a product metafield with the dynamic source icon.

Overview

A fully MIL-SPEC Nickel Boron coated AR-15 Bolt Carrier Group built to run hard, clean easy, and last. M16 cut carrier, Carpenter 158 steel bolt, magnetic particle inspected — everything correct, nothing cut short. 100% USA made.

FRT Compatible: M16 cut carrier is required for reliable function with the Partisan Disruptor FRT. This BCG meets that requirement. If you're building an FRT platform, see our Disruptor + HFRT Buffer Bundle — or add this BCG to complete the setup.

Specifications

Caliber	.223 Remington / 5.56 NATO
Finish	Nickel Boron
Carrier Cut	M16 Cut
Carrier Material	9310 Steel
Bolt Material	Carpenter 158 Steel
Extractor & Ejector	4140 Steel — Nitride Coated
Cam Pin	4140 Steel
Firing Pin	8740 Steel — Hard Chrome Finish
Gas Rings	MIL-SPEC
O-Ring	MIL-SPEC
Inspection	Magnetic Particle Inspected (MPI)
Origin	100% USA Made
Price	$159.99

Features

Nickel boron finish — harder, slicker, and easier to clean than phosphate or standard nitride
M16 cut carrier — required for FRT builds; compatible with all standard AR-15 platforms
Carpenter 158 steel bolt — MIL-SPEC standard, same spec used by military contractors
9310 steel carrier — high-strength alloy with excellent fatigue resistance
4140 steel extractor & ejector with nitride coating — added hardness and corrosion resistance
4140 steel cam pin — matched hardness to carrier for long service life
8740 steel firing pin with hard chrome finish — corrosion resistant, dimensionally stable
MIL-SPEC O-ring and gas rings — correct sealing and gas management from day one
Magnetic particle inspected — every bolt individually tested for surface and subsurface defects
100% USA made

Why Nickel Boron?

Nickel boron is harder and has a lower coefficient of friction than phosphate. That means less heat buildup, less fouling adhesion, and a BCG that wipes clean in seconds rather than minutes. It runs reliably with or without lubrication — important for high-rate-of-fire applications like FRT builds where the BCG cycles under greater stress and frequency than standard semi-auto use.

Combined with an M16 profile carrier and fully MIL-SPEC internals, this BCG is one of the most capable drop-in upgrades available for any mil-spec AR-15 platform.

FRT Compatibility

The Partisan Disruptor FRT requires an M16-profile BCG for reliable reset function. The M16 carrier tail provides the extended geometry that engages the Disruptor's reset lobe during the cycling stroke. A standard semi-auto carrier will not provide consistent reset. This BCG meets that requirement and is a direct recommended pairing for any Disruptor build.