Swaged Pellets and Air Rifle Bullets

Swaged Pellets are the premier ammunition for today’s high powered pellet guns.  PCP slugs or pellets, sometimes referred to boolits, can be produced in a couple of methods.  Swaged slugs offer the most consistent and accurate ammo on the market.

Swaging bullets or pellets involves using cold lead which placed into a die made of hardened steel to an exact diameter.  A punch from both the top and bottom of die are pushed towards each other with the inserted lead between them.  The swaging machine is set to stop when the two punches reach a certain distance between each other.

Corbin Swaging Press
Corbin Swage Press

This distance is what makes the bullet, or pellet, the overall length.  This also will dictate the weight of the pellet which is a combination of which base and nose it is made with along with the  overall length.  If you want a smaller pellet, simply make the two punches cycle closer together as the machine pushes the punches towards each other.  Or, further apart if you want a longer, heavier slug you make the punches stop further apart.

Swaging Punches
Swaging Punches to go into the hydraulic press

Because the die is a set diameter, when the pellet is made it is exactly that diameter.  Similar to a sizing die, the swage die is perfectly round and perfectly sized the pellets come out perfect each time.

Swaged Pellets vs Cast Bullets

Swaged pellet are made from cold lead.  As the lead in the swage dies is compressed is forms the shape of the die (diameter) and the nose shape of the nose punch and base shape of the base punch.  The lead inserted into the machine, called a core blank, has more lead that necessary to make the pellet.

As the punches are pushing towards each other and lead is fully formed inside the nose and base punches, the excess lead is bled through the die in small strips.  This makes the pellet come out perfect each time with the same weight from pellet to pellet.

Swaged boolits or bullets can be sized if needed.  Because the bullet started out perfect, the sizing die will make is a tiny bit smaller diameter but still very concentric.

Cast pellets are different.  They are made from molten lead which is poured into a mold.  After the mold cools it is opened and the boolits fall out into an awaiting vessel.  This method has some problems that are not associated with the swaging process.

Casting Problem 1

The mold is made from two pieces that fit together.  This is required for the process because that is how the bullets are released from the mold they were poured into.  The problem is there are tolerance issues with the two pieces fitting together, the better the fit, the better the pellet, the looser the fit, the worse the pellet will be.

Typical Casting Mold
Typical Casting Mold



Swaging uses a solid piece die making a perfect concentric pellet each time.

Casting Problem 2

Pouring pure lead can make some wrinkled and unfilled molds.  This makes the pellets not concentric, not the same each time, and can be heavier on one side or another which causes them to be inaccurate at longer ranges.

Wrinkled bullets on left
Wrinkled bullets on left

Many casters will add tin or other additives to the pure lead to make them cast better.  This can significantly increase the hardness of the lead. We have seen sellers selling these bullets for airguns saying it is soft lead at a BHN (lead hardness) of 10, not what we should be using.  Pure lead, like Nielsen Specialty Ammo uses, should be around 5-6 BHN.


Swaging wants to use pure lead because it is softer and easier to push through the swaging dies.

Casting Problem 3

Casting uses a mold which has a specific size in diameter and length.  It also will have a specific nose and base.  In order to change any of these factors requires another mold.  Each different nose, base, length or diameter requires a mold for each variant.  So if your gun wants a 145 grain bullet but the only mold is 175, that is all you can get.  If you want a slightly shorter or longer bullet than a caster can offer, too bad, they don’t have a way to make it.  If you want a different base or nose, same sad story.


Swaging offers many options within the caliber you order.  For example you may want to order a hollow base or boattail.  No problem, we insert that punch into the die.  You choose which nose you want, like a 3/4e round nose or a Keith nose.  Again, the machine is set with that nose.  Next you decide how long or heavy you want it, the machine is adjusted to make that exact pellet.  Any base, any nose and length.

Casting problem 4

The casting process uses molten lead to be poured into the die which can trap air in mold.  The air can not escape because the lead is so heavy so tiny air bubbles can be trapped in the mold.  This means there is no lead in that void since the air is taking up the space.  This can cause the bullet to be heavier on one side than it is on the other.  This can make the pellet wobble and cause it to be inaccurate, especially at longer ranges.


Swaging uses cold lead and bubbles are forced out under the extreme pressure the machines uses to compress the lead together.  This make a perfect pellet each time.

Casting does have it’s place in the air gun world.  If they are cast well they can be ok for plinking and are normally fairly cheap because they can be produced quickly by hand or by automated machines.



High Power Air Rifle Ammo