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Airgun Pellet Swaging

3/4-E ogive dual-diameter pellet Corbin makes pellet swage dies for conventional .177 and .22 airguns as well as the full spectrum of diameters for specialty and precharged high-power airguns, including 45 and 9mm rifles, .12, .14, 5mm (20 cal) and .25 caliber. Any caliber of airgun projectile can be made using Corbin equipment.

Please note: for the sake of brevity, airgun projectiles are refered to as "pellets", even though they are bullets of a special design and can properly be called bullets. Do not take offence at the term. It is just a short-hand way of saying "hollow based projectile designed for use with compressed air propulsion weapons".
click for specification page Years of providing equipment for world-class competitors to make precision standard caliber airgun projectiles have proved that a simple, straight-sided pellet with hollow base can be the most accurate and reliable design (in higher pressure hunting/defense airguns, the base may be flat, cupped, or dished rather than hollow). The two factors of greatest importance for small bore pellets or lower pressure guns are:
  • Diameter must be an air-tight fit to the chamber.

  • Skirt thickness must be proper for the air pressure at the muzzle.

Shank Diameter
In order to immediately obturate (seal) the air pressure at the instant of firing, the diameter needs to be very close to that of your gun's chamber. Because the base is hollow, with "skirts" of a carefully designed thickness for the available pressure, the pellet will expand and seal in the bore. Actual matching the bore size is far less important than fitting the chamber, for this reason. If the pellet is too large, it will be hard to insert and may be deformed from the seating pressure. If the pellet is too small, air will escape around it before it can expand fully, giving poor fit to the rifling. When it is sized for a mild press fit into the chamber, it will seal well and utilize all the available pressure for propulsion down the barrel and for expansion into the rifling grooves.

Therefore, the first thing to discover is the diameter of your chamber. If you have an existing pellet that fits well, measure it and use that diameter. Or, place a lead cylinder or pellet in the chamber, and use a flat-ended cleaning rod tip on a cleaning rod to compress the pellet and expand it to a good fit, then measure it. If you are concerned about your ability to measure accurately, send five or six sample pellets to Corbin. One pellet might be slightly "off" or get damaged in the mail. Five or six will give us enough to take an average and come up with a useful number for the new die diameter.

Skirt Thickness
standard pellet The skirt thickness is the dimension measuring the flange or wall thickness around the hollow cavity in the base. This is typically the thickness of just one side, so that a .222 diameter pellet with a hollow cavity that is 0.192 in diameter at the base would mean a skirt thickness of 0.222 minus 0.192 equals 0.030 inches remaining, divided by 2 equals a skirt of 0.015 inches.

(Again, not ALL pellets need a hollow base. Very high pressure PCP guns may do fine with a flat, dish, or cup base instead. But spring-air and lower pressure guns generally need the expansion potential of the hollow base to produce a good pressure seal and get all the available energy while still engaging the rifling properly.)

Skirt thickness has to be carefully balanced so that the skirt is strong enough NOT to be torn off or damaged from passage through the bore, thin enough to expand instantly when hit by the release of compressed air in the chamber, and thick enough so that it will not expand as the pellet exits the muzzle. This means you may want a different skirt thickness for different kinds of airguns, and even for different barrel lengths.

A spring-air piston gun might use a skirt of only 0.010 to 0.015 inch thickness. This is a fragile edge, not suitable for bulk packaging, which needs to be carried in a container with multiple holes in a foam insert so the pellets are not deformed. The pellets also need to be seated with a seating tool to avoid pushing on the thin edge (a seating tool typically fits into the base cavity and pushes inside it, rather than at the edge).

TC nose A pre-charged compressed gas gun might use a skirt of .025-.035 inch thickness, depending on the pellet weight and barrel length (and the pressure level). This is not "written in stone" but simply an example. You can tell if a skirt is too thin if the skirt is left in the barrel, or if the pellet expands at the base as it exits the barrel. This will give poor accuracy. Recovering a few pellets fired into Sim-Test or other ballistic gel or water will show expanded skirts. Making the skirt thicker eliminates these problems. You can tell if the skirt is too thick because the velocity will drop due to lack of a good seal, and accuracy will suffer due to lack of expansion into the bottom of the rifling grooves. Too thick a skirt is generally less harmful than too thin, if the pellet fits the chamber properly.

Tools Required
You can swage pellets either in your reloading press or in any of Corbin's swaging presses. The advantage of using your reloading press is that you don't need to buy another press. But the advantage of using a swaging press is 300% faster production, greater precision, and less manipulation of the components and tools (see Reloading Press versus Swaging Press for details).

Reloading Press
Pro-1-R Pro-Swage Die In a reloading press, you can use the PRO-1-R PRO-SWAGE DIE. Click the underlined name to read about this kind of die. Remember, the same tool and procedure applies regardless of the caliber you choose -- one die per caliber, of course, but we don't list every single caliber as we can make anything you want. The same die makes almost any weight, but you need to specify the diameter, the skirt thickness (if you know what you want, otherwise we go with the most commonly requested skirt), and the minimum and maximum weight you expect to make. Weight is adjustable, but we can move the range to cover a different span depending on what you want.

With a reloading press, your nose punch typically fits into the slotted ram. You can also precisely pre-adjust the lead core weight using a "weight-adjusting" punch, which is optional. Or you can just cut or cast the lead core as close as possible and use that. It won't be quite as precise as if you extruded surplus lead using the bleed punch and then formed the nose, but it will work better than most factory pellets, which are banged around in a bulk container before you receive them.

You may also want to include the optional "weight adjusting punch" which is a bleed-hole punch, allowing you to pre-adjust the core weight before forming the pellet. This gives you greater weight control and precision, but is not absolutely necessary for good pellets. In the Corbin swage presses, the dies have built-in weight adjustment which takes place as the pellet is formed, saving one step and one additional component, but this is not practical with the design of reloading presses.

Swaging Press

CSP-2 Press Pellets of .458 or smaller diameter can be formed in the CSP-1 S-press or the CSP-1H Hydro-Mite press, with -S type dies (1-inch OD body, 5/8-24 shank). Most people shooting spring-air guns will find the CSP-1 press with -S type dies to be exactly what they need, since the calibers are typcally under .458 diameter.

Pellets larger than .458 can be formed in the CSP-2 Mega Mite or the Hydro Press, with -H type dies (1.5-inch OD body, 1-12 threaded shank). Both the CSP-2 hand press and the CHP-1 Hydro Press are capable of 50 caliber, even up to 20mm.

A single-diameter pellet can be swaged in a LSWC-1-S die. This die fits into the ram of the CSP-1 press. It forms the base with an internal punch that also ejects the bullet from the die on the down stroke, and the nose is formed in a cavity in the end of the external punch. The edge of the punch forms a small shoulder, which gives this kind of bullet the general classification of "semi-wadcutter", regardless of the actual shape of the nose projecting beyond this shoulder. This kind of pellet has proven itself in international competition at the highest levels, provided the diameter is matched correctly to the chamber and the skirts are the proper thickness for the air pressure at the muzzle. (Too thick and there is poor expansion, too thin and the pellet base flares on exit from the muzzle, or separates in extreme cases.)

This is the complete package you would need for pellets of a given diameter, up to .458 size:
  1. CSP-1 S-Press, also for reloading your centerfire cartridges.

  2. LSWC-1-S Lead SWC die, with HB punch, TC nose: specify diameter.

  3. CSL-2 Swage Lube, a little goes a long way.

  4. LW-10 lead wire, closest diameter that is smaller than caliber.

  5. PCS-1 Core Cutter, with die insert to fit above wire.

If you wish, you can replace the lead wire and core cutter with the CM-4a core mold, and your own supply of soft lead.

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PINPOINT bullets Pellets with a smooth ogive and NO step shoulder can also be swaged using two different methods (in addition to the two different presses depending on caliber). The first method is to use a CSW-1 core swage die to create a precise cylinder of lead for the core, bleeding off surplus material to leave an exact weight on each stroke. Then this core is put into a PF-1 point forming die, which has a smooth ogive or nose shape diamond lapped into the die cavity itself. Since there is no "nose punch" per se (only a small ejection punch), there is no need for a shoulder on the bullet nose. The conventional PF-1-S or PF-1-H die has a spring-wire ejection pin to poke the bullet out by the tip, on the down stroke. It is automatic and greatly speeds up the operation: the bullet simply rises out of the die as the ram is retracted.

A second method uses a PF-1-SC or PF-1-HC custom version of the point form die. This custom version does it all in one stroke! It has bleed holes to extrude surplus lead and adjust the weight, it forms the base and the nose at the same time as it expands the core of lead to full diameter, and it has a pressure sealing, honed ejector punch fitted to a precisely sized ejection pin hole in the die. This pressure sealing ejector must be synchronized in length to the precise depth of the die cavity, which will vary slightly with the hand lapped die cavity in each die. A number marked on the die and on the punch head specifies the exact length, so that the die maker can replace the punch or the die without having to receive the old one back for measurement and syncronizing (which means adjusting the punch length so it comes exactly flush with the end of the die cavity).

The short-hand term "sync" is used to indicate on order forms that the punch is synchronized and pressure sealing fit to its die. A sync punch usually has a larger diameter ejector than a normal spring-wire ejector, and can be used to create a flat tip or a hollow point. Having a projection on the tip, a little smaller than the rest of the punch, will form a hole in the tip of the bullet. So you can, in one quick stroke, make a smooth ogive lead bullet with any sort of base design (flat, cup, dish, etc.) and adjust the weight, and create a hollow point cavity. All these operation might take several steps if used in separate dies, so the value of the custom PF die can not only save time, but may also be less expensive than several separate components.

The only caveat is that the sync punch is absolutely necessary to allow pressure build up sufficient to do all this in one stroke, so it adds the slight additional burden of keeping track of exact punch length, not mixing a sync punch made for one point form die with another one made for a different die, and always telling the die maker the sync number (or numbers) written on the die and punch when ordering a replacement. The ejection pin itself is removable from the punch head, so that you can replace damaged punches without having to buy the entire punch, just the PUNCH-HI or PUNCH-SI (which means, punch Insert).

Obviously, if you opt for the PF-1-SC or PF-1-HC for making pellets you do not need a CSW-1-H core swage. But, you can use one first to pre-form cores if you wish. The advantage may be, in some shapes and designs, that the ends will be more smooth or the edges less likely to have lube voids, etc. Don't worry too much about that unless it happens, because normally, it won't. Because people want all sorts of unusual designs for hollow points and nose and base shapes, there are some cases where the flow of material is such that it traps lube or otherwise doesn't want to fill out as well as usual. In those cases, pre-swaging the core can be the solution. Or changing the offending shape, of course! Swaging is mostly science, but there is a little art involved too...

Additional Items Needed:

LSWC-1-S die
  1. A way to make lead cores...
    • Lead wire (LW-10) of a size to fit easily into the die
    • A core cutter (PCS-1) of the same size
    • CM-4a core mold and your own lead supply
  2. Swage Lube (CSL-2)
Optionally, you may want to get additional nose punches, or base punches for different skirt thicknesses. A good selection would be:

  • Keith nose punch
  • 3/4-E nose punch
  • Conical nose punch
  • Target Wadcutter nose punch
  • Button Nose Wadcutter nose punch
  • Weight Pre-adjusting punch (PRO-SWAGE only)
click for design info

  • Flat base punch (extremely high power guns)
  • Dish base punch (very high power guns)
  • Cup base punch (extra high power guns)
  • Hollow base with .030 skirt (shorter barrel high power)
  • Hollow base with .025 skirt (medium barrel high power)
  • Hollow base with .020 skirt (longer barrel high power)
  • Hollow base with .015 skirt (medium or lower power short barrel)
  • Hollow base with .012 skirt (medium or lower power long barrel)
LSWC-1-S die

Note: We don't know exactly which skirt thickess is best for your particular gun, or exactly how long or how much pressure will work best with a given skirt. These are just rough guidelines to give you an idea of practical skirts. The only way to know what is best is to try it. Having a couple of extra punches lets you adjust the pellet design to match a different power level or barrel length.

Solution to Incomplete Tip or Base Formation

With thin skirts and sharp edges on the nose, especially in light weight hollow base pellet designs, it is possible that the pressure needed to flow lead into the narrow spaces within the die will be relieved through the weight-adjusting bleed holes in the die. This can lower the pressure below the point needed to make a nice, sharp edge or a complete finished base with a smooth, even edge.

If you are having this issue with a specific design, one solution is to get a special pellet swage internal punch, which has a removable nut on the tail end. This punch will sit higher in the die with the nut attached, blocking the bleed holes so that lead pressure will be able to rise and fill out the pellet edges and base. The nut unscrews so that the punch drops further into the ram, exposing the bleed holes. Then the same die can be used both as a core swage, to adjust the core weight with the nut removed, and as a core seater, with the nut installed, to block the bleed holes.

This will work if the pellet length and weight is small enough so the space left in the lead semi-wadcutter die, with the bleed holes blocked by the internal punch, is still long enough to hold the complete pellet and a caliber or two length of the external punch (for alignment). Usually, an airgun pellet is relatively short compared to its caliber, so this will work. It does not work for any bullet that is longer than a caliber length less than the distance from the bleed holes to the die mouth.

Internal punch with nut installed Internal punch with nut installed for swaging pellet shape, blocking bleed holes < High

Extrusion >
Internal punch with nut removed Internal punch with nut removed for adjusting the weight in first step

To order this special punch, order an internal punch for the desired caliber (PUNCH-SC 220 INT LSWC, for instance). Then add the words "Adj.Bleed Hole Blocker". This is a "custom" punch which is not usually in stock, but it can be made to order rather quickly.

Other Information...
Pellet made in the LSWC-1 die Shotgun Slugs are different from airgun pellets primarily in their weight and diameter, but not so much in their general design and tools. You can make a .410 shotgun slug even in a reloading press or the S-press. You can make 20 and 12 gauge slugs in the Corbin Hydro Press (and, with some effort, in the large CSP-2 Mega Mite hand press) using -H type dies. Viewed from a distance, the shotgun slugs would look similar to airgun pellets and vice versa!

If you would like to make dual diameter pellets, or pellets without the small SWC shoulder caused by using a nose punch (the edge of the punch can't be zero thickness, and that's what forms the little SWC shoulder), it can be done using other special dies. But in general, the best results and lowest cost, easiest operation and highest production is with the straight sided, SWC-shoulder style of pellet, which is very much like a match pistol bullet except for the particularly thin skirts and hollow base depth. In fact, the same tools are used to make hollow base pistol bullets, with a different diameter swage die but the same LSWC-1-S, LSWC-1-H, or PRO-SWAGE style having a somewhat thicker skirt and shorter hollow cavity in the base.

You can order directly on www.SwageDies.com secure web store by clicking the "padlock" symbol at the top of nearly all web pages.

PO Box 2659, White City, OR 97503 USA

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Diana dual pistol recoilless single stroke spring air gun Can you tell what's wrong in this picture? Diana dual pistol recoilless single stroke spring air gun Diana dual pistol recoilless single stroke spring air gun
The Diana Model 10 used two pistons, one moving backward to cancel the momentum of the main piston compressing air behind the pellet, resulting in virtually no spring/piston recoil. The trigger could be adjusted for position, overtravel, pretravel, and two levels of trigger force. Both the front are rear sight had click adjustments. The front sight adjusts for profile width, and the rear for windage and elevation. The "barrel weight" is a rotating grip that covers the sights and forms a handle, used to "break" the barrel downward to cock the gun. The gun cannot be fired until this cover is rotated back under the barrel, after cocking. At 30 meters, the gun could put five 177 caliber pellets into a single ragged hole (the same might not always be said for the shooter).