Spikes Tactical FN barrel steel is 21CrMoV511

[stahljaeger]

I just got a new Spikes Tactical CHF 14.5" mid length barrel

It is marked with:

ST FN DIN 21CrMoV511 CHF 5.56 NATO 1/7 CL HP MP

I looked up 21CrMoV511 to try and learn more about that steel

Its composition

Carbon (C) 0.17-0.25
Silicon (Si) 0.30-0.60
Manganese (Mn) 0.30-0.60
Phosphorus (P) 0.035 max
Sulfur (S) 0.035 max
Chromium (Cr) 1.2-1.5
Nickel (N) 0.60
Molybdenum (Mo) 1.00-1.20
Vanadium (V) 0.25-0.35

Tensile Strength 650-880 MPa (94,270-127,630psi)
Yield Strength 350-550 MPa (50,760-79,770psi)
Fatigue 275 MPa (39,880psi)


It is used for components operating at temperatures up to 540C

Here http://www.spikestactical.com/new/z/forum/viewtopic.php?f=8&t=1789 Spikes implies this is the steel used in the M249 barrels but doesn't actually say that.

Is this the infamous "machine gun steel?"

Does anyone know more about this steel?

[JBowles]

I just got a new Spikes Tactical CHF 14.5" mid length barrel

It is marked with:

ST FN DIN 21CrMoV511 CHF 5.56 NATO 1/7 CL HP MP

I looked up 21CrMoV511 to try and learn more about that steel

Its composition

Carbon (C) 0.17-0.25
Silicon (Si) 0.30-0.60
Manganese (Mn) 0.30-0.60
Phosphorus (P) 0.035 max
Sulfur (S) 0.035 max
Chromium (Cr) 1.2-1.5
Nickel (N) 0.60
Molybdenum (Mo) 1.00-1.20
Vanadium (V) 0.25-0.35

Tensile Strength 650-880 MPa (94,270-127,630psi)
Yield Strength 350-550 MPa (50,760-79,770psi)
Fatigue 275 MPa (39,880psi)


It is used for components operating at temperatures up to 540C

Here http://www.spikestactical.com/new/z/forum/viewtopic.php?f=8&t=1789 Spikes implies this is the steel used in the M249 barrels but doesn't actually say that.

Is this the infamous "machine gun steel?"

Does anyone know more about this steel?

It's basically the same as 4150 CMV but with a lower carbon content and nickel added, the lower carbon content makes it a bit easier to work and I assume the nickel is there make up for the loss of hardenablity and adds some toughness. The reason this steel is used is because it hammer forges' better than 4150.

[eodinert]

I believe that 'machine gun steel' verbiage comes from FNs marketing material.