Boeing BMS Specification 300M / 4340M Low Alloy Steel Alloy Steel

BMS 7-26

300M / 4340M Low Alloy Steel – Steel Bars, Forgings & Tubing

Steel, 0.82Cr – 1.8Ni – 0.40Mo – 0.40–0.44C – 1.60Si – 0.08V, Consumable Electrode Vacuum Remelted, Normalized and Tempered

AS9100D / ISO 9001

Mill Test Reports

2–4 Week Delivery

877-237-6822

Quick Specification Facts

Spec Number BMS 7-26 (BMS7-26)

Material 300M / 4340M Low Alloy Steel

Spec Type BMS (Boeing Material Specification)

Category 300M & 4340M Alloy Steel

Composition 0.82Cr – 1.8Ni – 0.40Mo – 0.40–0.44C – 1.60Si – 0.08V

Condition Consumable Electrode Vacuum Remelted, Normalized and Tempered

Product Forms Steel Bars, Steel Forgings, Steel Tubing

Certification AS9100D / ISO 9001 with full MTR traceability

Specification Overview

BMS 7-26 (also referenced as BMS7-26) is a Boeing Material Specification covering 300M / 4340M low alloy steel in the forms of bars, forgings, and tubing. The material is produced by consumable electrode vacuum remelting (CEVM) and is supplied in the normalized and tempered condition. The nominal chemistry of 0.82% Chromium, 1.8% Nickel, 0.40% Molybdenum, 0.40–0.44% Carbon, 1.60% Silicon, and 0.08% Vanadium delivers an outstanding combination of ultra-high tensile strength, high impact resistance, and excellent toughness – making it one of the premier high-strength steels for critical aerospace applications.

300M steel (also known as 4340M) is a modified version of 4340 alloy steel with increased silicon content and the addition of vanadium, which significantly elevates the ultimate tensile strength while retaining excellent fracture toughness. The vacuum remelting process ensures exceptional cleanliness and homogeneity, minimizing inclusions and improving fatigue life. BMS 7-26 material is widely used in aircraft structural components, landing gear, and other flight-critical parts requiring the highest levels of structural integrity.

Available Product Forms

Steel Bars

Steel Forgings

Steel Tubing

BMS 7-26 material is supplied as Steel Bars, Steel Forgings, and Steel Tubing per specification requirements. Round bars are available in a range of diameters; forgings are produced to near-net or custom shapes; and tubing is available in standard and custom outside diameters and wall thicknesses. Contact our materials specialists for non-standard dimensions or special processing requirements.

Nominal Chemical Composition

Element	Symbol	Nominal %	Notes
Carbon	C	0.40 – 0.44%	Medium-high carbon – enables ultra-high strength after heat treatment
Silicon	Si	1.45 – 1.80% (~1.60%)	Key modifier vs. 4340; significantly raises tensile strength and hardenability
Chromium	Cr	0.70 – 0.95% (~0.82%)	Improves hardenability and corrosion resistance
Nickel	Ni	1.65 – 2.00% (~1.8%)	Enhances toughness, impact resistance, and hardenability
Molybdenum	Mo	0.30 – 0.45% (~0.40%)	Enhances hardenability and elevated-temperature strength
Vanadium	V	0.05 – 0.10% (~0.08%)	Grain refiner; improves strength, toughness, and fatigue resistance
Manganese	Mn	0.65 – 0.90%	Deoxidizer; improves hardenability and strength
Iron	Fe	Balance	Base metal

Chemical composition ranges are nominal. Consult the current issue of BMS 7-26 for precise minimum/maximum requirements. Aero-Vac provides full mill test reports (MTRs) with certified chemistry for every order.

Key Properties & Specification Details

Property / Attribute	Details
Specification Number	BMS 7-26 (BMS7-26)
Issuing Organization	Boeing (Boeing Material Specification)
Material Type	300M / 4340M Low Alloy Steel – Bars, Forgings, Tubing
Steel Grade	300M (4340M) / UNS K44220
Nominal Composition	0.82Cr – 1.8Ni – 0.40Mo – 0.40–0.44C – 1.60Si – 0.08V
Melting Practice	Consumable Electrode Vacuum Remelted (CEVM)
Condition	Normalized and Tempered
Available Forms	Steel Bars, Steel Forgings, Steel Tubing
Tensile Strength	Ultra-high – typically ≥280 ksi (1930 MPa) in hardened and tempered condition
Impact Resistance	High – excellent toughness relative to strength level
Hardenability	Excellent – deep hardening through large cross sections
Fatigue Resistance	Very High – enhanced by vacuum remelting and vanadium addition
Magnetic Properties	Magnetic (ferritic/martensitic)
Certification Available	AS9100D / ISO 9001, Certificate of Conformance, MTR

Typical Applications

Aerospace & Aircraft: Landing gear components, aircraft structural members, wing fittings, bulkheads, engine mounts, and other flight-critical applications requiring ultra-high tensile strength combined with excellent fracture toughness and fatigue resistance.

Spacecraft & Defense: Missile and rocket motor cases, launch vehicle structural components, spacecraft fasteners and fittings, and defense applications demanding maximum strength-to-weight ratio under extreme loading conditions.

Motorsports: High-performance racing suspension components, drivetrain parts, roll cage elements, and other high-load structural applications where the exceptional strength-to-weight ratio of 300M provides a competitive advantage.

High-Load Structural Applications: Pressure vessels, ultra-high-strength fasteners, tooling components, and structural assemblies where conventional high-strength steels are insufficient to meet weight and performance targets.

Forgings & Machined Components: Near-net-shape forgings for aircraft parts, precision-machined structural components, and custom aerospace hardware where the unique properties of 300M / 4340M vacuum-melted steel are specified by design engineers.

Frequently Asked Questions – BMS 7-26

What is BMS 7-26 and what does it cover?

BMS 7-26 (also written BMS7-26) is a Boeing Material Specification covering 300M / 4340M low alloy steel in the forms of bars, forgings, and tubing. The material is produced by consumable electrode vacuum remelting (CEVM) and supplied in the normalized and tempered condition. The nominal chemistry of 0.82% Chromium, 1.8% Nickel, 0.40% Molybdenum, 0.40–0.44% Carbon, 1.60% Silicon, and 0.08% Vanadium delivers ultra-high tensile strength combined with exceptional impact resistance and fatigue life. BMS 7-26 is widely used in aerospace, spacecraft, and motorsport applications requiring the highest levels of structural performance.

What is the difference between 300M steel and 4340 steel?

300M (also called 4340M) is a modified version of 4340 alloy steel. The key differences are the significantly elevated silicon content (approximately 1.60% vs. 0.15–0.35% in standard 4340) and the addition of vanadium (approximately 0.08%). These modifications substantially increase the ultimate tensile strength of 300M compared to 4340 – typically achieving ≥280 ksi (1930 MPa) vs. 4340's typical range of 200–260 ksi depending on heat treatment. The vacuum remelting process used for 300M / BMS 7-26 further improves cleanliness and fatigue performance over air-melted 4340. For design-critical aerospace applications where maximum strength-to-weight ratio is required, 300M under BMS 7-26 is frequently specified.

Does Aero-Vac supply BMS 7-26 with full mill test reports and certifications?

Yes. All BMS 7-26 material supplied by Aero-Vac is fully traceable to mill test reports (MTRs) confirming chemical composition and mechanical properties per the specification. We are AS9100D / ISO 9001 certified with a 99.6% quality rating. Every order ships with certificates of conformance, material certifications, and chemical/mechanical test reports. Electronic delivery of all documentation is available for fast turnaround. If your Boeing program requires additional special process certifications or source approvals, our quality team can coordinate as needed.

What sizes of BMS 7-26 material does Aero-Vac stock?

Aero-Vac maintains inventory of BMS 7-26 steel in bars, forgings, and tubing across a range of standard sizes. Round bars are available in diameters from small cross-sections up to large billet sizes; tubing is stocked in standard OD and wall thickness combinations. For custom forging shapes, near-net forgings, or non-standard dimensions, our team can source from our global supplier network or arrange custom mill production. Contact us with your specific size requirements and we will provide a prompt quote with availability and lead time.

What are the typical lead times for BMS 7-26 material?

In-stock BMS 7-26 material is typically available for same-day or next-day shipment. For custom-cut or specially processed orders, our standard lead time is 2–4 weeks—significantly faster than the industry average of 8–12 weeks. Custom forgings or specialty items requiring mill production may require 4–8 weeks depending on quantity and dimensions. We prioritize urgent aerospace and defense requirements and will always provide honest, upfront delivery estimates. Rush processing is available on select items. Contact our team to discuss your specific timeline.

Can Aero-Vac provide value-added processing for BMS 7-26 material?

Yes. Aero-Vac operates a complete in-house processing facility at our Port of Kalama location. For BMS 7-26 300M / 4340M alloy steel, we offer precision saw cutting, surface grinding, turning, milling, and heat treatment services. We also provide comprehensive mechanical and non-destructive testing services in-house. Having all capabilities under one roof allows for faster turnaround, tighter quality control, and reduced overall cost compared to using multiple vendors. Contact us to discuss your specific processing requirements, including custom forging coordination and machining to near-net shapes.

Need BMS 7-26 material or a custom quote?

Our alloy steel specialists can provide fast pricing, availability, and technical guidance for your BMS 7-26 / 300M low alloy steel requirements.