The pilum, or javelin is a very dangerous weapon and is designed to kill individual opponents while at the same time breaking the cohesion of a body of enemies – it is a charge-breaker – and was thrown immediately before contact, at ranges between 15 and 25 meters.  The small point could penetrate a shield and wound the man behind it, or even pierce armor.   It has often been said that the pilum was designed to get stuck in an enemy's shield, forcing him to discard it, but of course its primary function was to kill.  However, the shield-disabling capabilities of the weapon would be a very visible and important side effect!  A shield with a pilum stuck firmly in it would be very cumbersome, due to the leverage of the shaft.  An oncoming Roman would be able knock the shaft aside to pull the victim's shield out of place, or simply step on it (if it's close enough to the ground) to rip the shield out of the hand.  If the pilum is loose in the hole it has made, the buttspike will dig in and act like a doorstop, possibly very suddenly.   There would only be a few seconds from the time the pila hit to the moment when the Romans arrive with swords and shields ready, not long enough to set a shield down and yank out a pilum.  One can well imagine the effect of hundreds of pila crashing into a line of barbarians who are just starting to charge.  As well as those wounded and killed outright, many men will suddenly be tripping over pila and shields, or trying to stop and back up to remove pila from their shields (or bodies!), thus disrupting the entire formation and stopping the impetus of an enemy’s charge.

The javelin or pilum consists of a long iron head with a small point, and a wooden shaft.  On the most common type, the bottom of the head widens into a flat tang, which is riveted into the widened top of the wood shaft.  The second type has a socketed head, and a third type, less well-known, has a spike tang.  In the first century AD, some tanged pila are shown with a spherical weight, presumed to be lead, behind the joint block.  Apparently the weapon had become lighter over the centuries, and the weight was added to increase its "punch".

Pilum heads are 14" to 30" long, with pyramidal or barbed points c. 2" long.  The iron shanks are about 1/4" thick (round) below the point, swelling to c. 3/8" or 1/2" square at the base.  The tang is an inch or more wide, and can be rectangular or slightly flaired.  (Before forging the tang, it's a good idea to fold up c. 6" of the shank, then flatten, to strengthen the tang and allow more width.)  There is no evidence that the points were specially hardened--they penetrate simply due to their shape.  Likewise, the iron shank cannot really be described as "soft", it bends on impact because it is thin.

The wood shaft is made all in one piece, generally ash, though oak or hickory are also acceptable.   Overall it is 4 to 5 feet long, making the complete weapon 5-1/2 to 7 feet in length.  Most of the length (or all of it, for a socketed pilum) is round in section, about 7/8" to 1-1/8" in diameter.  At the top of the top of the shaft is the tapered, square-section "joint block", 5" to 8" long.  It is slotted to receive the tang, and capped with an iron ferrule or collett which is secured by 2 little iron wedges.  (Since the ferrule is also tapered, it works best to allow a little of the wood to project above it, to be splayed out by the wedges.)  Two or three rivets hold the tang in place; a socketed head needs only a small nail.

All iron parts of the pilum should be black from the forge, imitated if necessary by heating the piece and wiping it with oil.  The buttspike is a cone made by wrapping a triangle of sheet steel (20-gauge).  The point is sometimes hammered into a square-section spike, but the seam is usually not forged shut.  It is secured to the shaft with a small nail.  The head can be riveted to the shaft with regular nails if you first heat the heads red hot and give them a few raps with a hammer to make them look forged.  Use a washer at both ends of the nail and peen the end flat like a regular rivet.  Washers can be cut from blackened sheet steel with a cold chisel; round washers can be used but first remove any galvanization and blacken them.

 
The wood may be treated with linseed oil, but should not be stained.  An ash 2x2 can be worked down to the proper shape by first sawing the shaft section down to 1" square, then using a drawknife and rasp to round it.  Then saw the joint block to its desired shape.  Starting with a hole-digger handle--mostly round with a square-section end--is another option.

       Click on the image at left for a larger version.  The junction blocks of two pila are shown, one with two rivets and one with three.  Next to them is an unmounted pilum head showing the flat tang, as well as a ferrule, two nails with forged heads, washers, and a buttspike of wrapped sheet steel (3-3/4" long).

       At right is a typical point, roughly full size.  Below is a socketed pilum head by Mark Morrow (click for a larger view).  It is 24" long and weighs about 12 ounces.

       If your pilum head bends when thrown (as it should!), and you wish to avoid stressing and eventually breaking the metal by simply bending it straight again, heat the bend red-hot with a propane torch or in a forge, and quickly hammer it back into shape.  Do not quench it in water to cool it!  (See the page on Armoring Hints.) 

       A couple original pilum heads can be seen here: http://www.romancoins.info/MilitaryEquipment-spear.html.