Barrels for Nerf

At this moment this page only focuses on the ~53 caliber barrels as this is the most common size.

* Little information about this steel was provided so a weak carbon steel's data was used. This may not be accurate, though, few'll care because steel is a very uncommon barrel material.

What the table means

MMC# refers to the material's product number at McMaster-Carr except for PETG, which links to One Man Clan's PETG sales thread.

OD is the outer diameter of the tubing. Units are inches.

ID is the inner diameter. Units are inches.

rho is the density of the material. Units are lb/in^3.

E is the modulus of elasticity of the material. This is a measure of how easily the material deforms. Higher numbers deform less for a certain load. Units are psi.

Sy is the yield strength of the material. This is the amount of stress the material can take before permanently deforming. Units are psi.

E*I is the modulus of elasticity multiplied by the area moment of inertia of the tube. This describes how stiff the tube is. A stiff tube can not be bent easily. Stiffer tubes are more resistent to bending from their own weight and being struck. They also are resistent to vibration, which does reduce accuracy in firearms but probably has no effect in Nerf. Units are lb*in^2.

Ur is called the "modulus of resilience". It represents how much energy the material can absorb per unit volume before permanent deformation occurs. Because the modulus of resilience depends solely on the material properties and not the geometry, it is multiplied by the tube thickness so that comparisons about the dentability of the material can be made.

To determine if the material will at least yield from being struck, find the "kinetic energy density" of the material impacting the tube and compare it against the value of Ur*t (units are lb*in/in^2). The kinetic energy density is the kinetic energy multiplied by the impact area.

def is how much the free end of a horizontal 36 inch barrel will sag in inches calculated with elementary beam theory. The bending is exaggerated with longer barrels, hence why I used a longer barrel here. The variables involved are barrel length, linear density (lb/ft), and stiffness (E*I).

Pcr is the critical buckling load in pounds for this barrel with a length of 12 inches. Basically, this is how much force must be applied at the end to bend (buckle) the barrel. This really only shows in Nerf when blasters are dropped on their barrels or when barrel tapping.

Each material in summary

CPVC:

Pros: Reasonably cheap. Excellent impact strength.

Cons: Heavy.

PVC:

Pros: Cheap. Excellent impact strength.

Cons: Heavy.

PETG:

Pros: Cheap. Lightweight. Clear.

Cons: Terrible stiffness. Prone to damage. Extremely low critical buckling load.

Al (6063-T5)

Pros: Cheap. Reasonably lightweight. Very stiff.

Cons: Will dent easier than other aluminums.

Al (2024)

Pros: Reasonably lightweight. Very stiff. Good impact strength.

Cons: Expensive.

Al (6061-T6)

Pros: Reasonably lightweight. Very stiff. Good impact strength.

Cons: Could be cheaper, but is not expensive.

Brass

Pros: Can telescope. Reasonably lightweight. Stiff.

Cons: Very easy to dent. Tarnishes.

Steel

Pros: Extremely stiff.

Cons: Extremely heavy. Could be cheaper, but is not expensive.

Copper

Pros: Extremely stiff. Good impact strength.

Cons: Extremely heavy. Could be cheaper, but is not expensive.

Stainless steel

Pros: Extremely stiff. Shiny.

Cons: Extremely heavy.

Observations

Aluminum and brass are comparable. The primary differences between the two is that aluminum is not designed to telescope like brass, brass can dent far easier than aluminum (shown in the Ur*t column), and aluminum is a little more than twice as stiff.

The differences between the different types of aluminum are subtle. They vary only in yield strength and price in this table. The differences in yield strength are amplified in the impact strength before permanent deformation column. Given only minor differences, there is little reason to buy the stronger alloys, at least from McMaster-Carr. Other places (such as Online Metals) may have different prices and stronger alloys may be cheaper and thus worthwhile.

PETG wins huge in weight. However, PETG also loses huge in many strength categories. A thicker walled PETG with the same ID would be desirable. Another clear plastic such as polycarbonate might also be a good idea.

PETG has absolutely terrible stiffness. This is shown quite evidently in the critical buckling load, which is less than 10 pounds. Either be careful with PETG, sleeve it in something else (which would make it much heavier), or use it in a structure like a turret where the geometry would increase the stiffness.

In terms of price, PETG and sch. 80 PVC are winners. 6063 aluminum is the next closest.

The heavier metals, steel, copper, and stainless steel, are rare, and rightly so. They are very strong by virtue of their geometry and material, however, they are also extremely heavy.

Which should I use? / Which is best?

Use materials that are readily available to you and fit the darts you intend to use. For spring blasters you want a tighter fit to allow pressure to build higher due to the slow initial flow. For pneumatics you want a smooth fit because too tight fits introduce non-negligible energy losses to friction, however, be sure that the fit is not loose or energy losses to leaks around the dart will occur.

As all of these materials have approximately the same diameter (until additional tables of different average calibers are made), your decision relies on the properties of the material.

When you want something to telescope, brass is the best choice as it was designed to telescope.

If you want optical clarity and/or low weight, PETG would be a good choice.

If you want a material that mixes a variety of properties, 6063 aluminum is cheap, strong in all measures, and reasonably lightweight.

Other useful links

• Barrel materials @ NerferWiki
• Guide To Barrel Material @ NerfHaven

Sources

Most data was taken from each product's respective McMaster-Carr page or from memory.

http://www.harvel.com/tspp-cpvc-pipe.asp

http://www.harvel.com/tspp-pvc-pipe.asp

http://www.visipak.com/materials.html

http://www.visipak.com/clear_plastic_tubing.shtml

http://www.nacobre.com.mx/ing/En_CI_Brass%20%20260.asp

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©2007 - 2010 Ben Trettel
Last modified on 2009-04-08 22:32:27.