How to Use a Corbin S Press - A Thread Geared Toward Beginners

Setting up Your Corbin Precision Core Cutter:​

It is sold separate from the press, unless you get a package deal (press, die set, cutter, lube, wire). Approx $100 by itself. If you’re handy you can probably make your own. In my opinion it’s not a must buy item.


Diagram of the Corbin Precision Core Cutter


I used an old piece of scrap countertop so I can move the cutter around and mount it in various orientations. I’m thinking about using C-clamps to hold this section of countertop to my workbench. An issue I already encountered was that since I didn’t install the bench stand in an area with mounting the cutter on this in mind, the scrap wood is a little wide and hangs over the edge a few inches. I was able to hold it with one palm resting flat and two spools of lead wire on top of it to weigh it down until I dig out some clamps.


Poorly thought out bench stand placement in relation to the core cutter mount.


I used these wood screws and two small washers to affix the cutter.


Before cutting cores, be sure to tighten this grub screw on the bottom of the cutter. It holds the die (bushing) in place. Blue Loctitie is definitely recommended on the grub screw securing the dies.


If you do not, the die can get stuck on your lead wire. It’s not extremely hard to remove, but why deal with the annoyance if you don’t have to? When I first used mine it took a few minutes for me to understand why the die started coming off with the lead wire strand.


I secured it with a 5/64 Allen wrench. You may want to use Loctite or Vibratite on this grub screw. Mine keep coming loose while cutting cores. Within the core cutter there are two dies (bushings) that the wire feeds through and both can loosen up with use. When the pictured die (bushing) comes loose, be sure to bend the cutter arm 45º to 90º before replacing the bushing. If you do not, you will insert it too far and will not be able to push the handle down to cut cores. In a worst-case scenario, you may damage the die if you really try to force the cutter handle down onto the die (bushing) installed too deep (going into holes for the top and bottom dies/bushings in the arms on both sides of the pivot) and obstructing the handle.



Then I used a 3/32 drill bit to pilot shallow holes on the marks to start the wood screws. Sorry, no pic of the holes drilled.


Next I aligned the holes of the cutter mounting bar up over the pilot holes, placed washers over the screws, and started to screw them into the pilot holes by hand. I then used an electric driver to fasten them through the holes in the mounting bar to secure the cutter. The result is the first photo of the cutter mounted earlier in this post. I thought that mounting the cutter perpendicular to the tabletop would allow the cut cores to easily drop into my box below. They do not drop down each time. I have to push or pull them with my fingers. Sometimes they will drop into my hand on the downstroke. I’m cutting .340” wire. I may change my mounting position if this continues.

I like the core cutter the content creator made in the following link

Cutting Cores:​

The first step is to clean the lead wire. There are various ways to do do this. You may use a Scotch Brite pad (green or red) or a copper pot scrubbing pad (DO NOT USE STEEL WOOL OR STEEL PADS) to scrub dirt, dust, and grime off of the surface of the lead wire. Next, wipe to down with oil or an organic solvent (I use acetone). Clean and wipe the wire in 18"-24" sections at a time. Then, cut your cores. Initially I didn’t change the settings on the core cutter from the way that it arrived. Doing so I dropped cores roughly around 8 grams or 123 grains. Thank you @Long_Shot for reminding me to add the wire cleaning step and for the Scotch Brite suggestion.

Spool of .34 pure lead wire.


Corbin core cutter with box below to catch cut cores. I like using an empty egg carton to catch the cores and lead flakes from the cutter.


Wire being fed into cutter to cut cores. Be sure to feed the wire in all the way to the stop screw.


Cores in box that need to be weighed and pressed into slugs.


Weighing random cores throughout the process helps me to keep track of consistency. Because the nut on the stop screw in the core cutter loosened and I moved the stop screw, my cores are different sizes. Others had to be cut with wire cutters because the lead wire was so twisted and bent up at certain points it was hard to feed it into the dies without the edges digging into the wire. The reason the wire was bent up so much at certain points because I’m still getting my workspace organized and I did not have the wire spool hanging or situated in a place that allowed a continuous and easy feed into the cutter without bending or twisting it.


Cores that I cut from .34 wire using the Corbin core cutter.

Setting Up Dies to Swage in the Corbin S Press:​

Before you begin, determine which sort of projectile you want to swage. Here I’m swaging a hollow-ogive, hollow point, flat-base slug. 125 grains is the target weight.

This is a two-part swaging process.
Pt.1, Step 1 - Select the dies and punches. Once I select a die and internal punch set, I use a clean shop towel or clean cloth dampened with acetone and several acetone soaked Q-tips to remove oil from the punches and from within the bores of the die(s). I let them sit a few minutes to allow the acetone to evaporate.

.357 die with an internal hollow-ogive punch.


Pictured below are a die and internal hollow-ogive punch separated. The die is on the right, the punch on the left. Notice the nipple on the bottom of the internal punch? This can be used to differentiate an internal punch from an external punch (which will be flat on the bottom non-polished portion).


Profile shot of die and hollow-ogive internal punch put together. The threaded portion of the bottom of the die screws into the ram.


Pt.1, Step 2 -Insert external punch (that forms the bottom of the projectile) into the floating external punch holder at the top of the S Press (above the die and ram). To do so you must unscrew this floating punch holder retainer at the bottom of the external floating punch holder.



Hold the retainer's threads facing up and carefully insert the punch through the retainer. Try not to scrape the polished portion of the punch or its finely machined edge on the inner diameter of the retainer. Screw in to the top, but leave the nut loose.


Insert the base of the punch into the external floating punch holder, align the retainer nut's threads, and screw into the punch holder. Two hands may be best so you do not drop your punch.


Pt.1 Step 3 - align threads on the die with those in the ram. Insert threaded base of punch into the ram. You can hold the punch with your off hand to prevent it from falling out.


Then screw the die into the ram.


Here's the die screwed all the way into the ram. The small hole seen midway down the body of the die is where the sprue (excess lead) exits the die. The catch tray is easy to install by slipping it over the die, working it down past the bleed hole.


I’m not sure if there is a specific order that is preferable for installing the punch and die. I think it’s best to install them in the order that affords you the most room to move your hands and punches in and out of that space without bumping the punches into anything.

Swaging a Projectile:​

Pt.1, Step 4 - Select a cut core that’s around 4-5 grains heavier than the target weight of the projectile you wish to swage. The more you do this I think the more precise you can be with the core’s weight being closer to the finished projectile’s weight. Roll the core around on a lubricated surface or lube your fingers and rub lube around the projectile (I use Corbin Swage lube. It doesn't take much). Don’t forget to lubricate both cut ends of the core. Then place it on top of the center of the opening on the die or atop the punch. If you place it on the punch you’ll have to hold the core while slowly pushing the ram up until it meets the above punch. Be careful not to pinch your fingers /gloves between the punch and core. Be sure to guide the core so that that bottom of the core enters the die with little resistance.


Here’s a photo of the core being formed. Notice the excess lead being extruded (ejected) from the die through the bleed hole forming thin strands of sprue. Pay close attention to the line going around the external punch. This is the limit line. It should always be visible above the face/top of the die. lowering it further risks damaging your external punch and the bore of your die.


Pt.1 Step 5 -Remove formed core. Below is a hollow-ogive core formed atop the die ending the first step of the two-step process. Depending upon the depth of the hollow in the ogive, it may difficult to remove the formed core from the punch with slippery gloves. Keep a clean dry cloth or paper towel close so you can use it to grip the core in order to remove it easier. It may take a tight grip using the dry cloth (between your fingers) and a small amount of force to twist and pull the lubed formed core up and off of the punch. It shouldn't take a lot of force, if it does you likely didn't use enough lube on the ends. If you pull too hard you may risk hitting the base of the formed core against the external punch above. I'm mindful not to touch the punch in the floating pouch holder with the cloth. I don't want to introduce dust or debris into the die. Notice that the punch has lube that has accumulated on it making it easier for foreign particles to stick to it. Brush any lead flakes off of the surface of the die and into the catch tray below.


Complete forming of the hollow-ogive cores. There’s an unformed core on the stamp pad. I used a blank stamp pad that is usually used to soak up ink for rubber stamps to hold lube to lube cores. I poured a small amount of Corbin swage lube on the pad, used a finger to smear lube across the pad to absorb it so that I can roll cores around on the pad in order to lube cores before swaging. I tried swaging a core without lube. I had to use pliers to gently work it off of the hollow-ogive punch. Don’t do it! @Ca_Varminter thanks for the blank stamp pad suggestion.


Pt.2, Step 1 - Unscrew and remove the hollow-ogive punch and die from the ram.


Pt.2 Step 2 - Select a hollow-point forming die and punch set.


Install them into the ram the way that you installed the previous punch and die set.


Pt.2, Step 3 - Select a formed core to press into a slug. Be sure that the formed core has adequate lube around the cylinder and around the rim of the hollow.


Place the formed core (open cavity facing down) onto the die face over the opening of the hollow-tip forming punch.


Pt.2, Step 4 - Press the formed core into a hollow-ogive, hollow-point slug.


Pressing the formed core into a slug.


Pt.2, Step 5 - When you lower the ram you should see an inverted hollow-point slug. At this stage rotate the slug 180º as it sits on the die, then raise the ram again pressing the slug a second time to ensure a more uniform shape and weight. Finally lower the ram and remove the slug.

Pt.2, Step 6 - Weigh it if you like and start pressing the next formed core into a slug. This slug was a tenth of a grain under my target weight which is acceptable to me.


Pt.2, Step 7 - Sort slugs by weight. Those that come out too heavy (less than 5 grains over the target weight) will be reformed to the closest lower weight that is a multiple of five (a 127 grain slug will become 125 grains). Those that come out too light will be swaged down to the next lowest grain weight that is a multiple of five (a 123 grain slug will become a 120 grains).

Weighed and sorted slugs.



Finally I use shop paper towels or clean cloth lightly soaked with acetone to wipe the outside of my dies & punches. I use acetone dampened Q-tips to clean the bores of the dies and to wipe the bores with dry Q-tips until they come out fairly clean. Next I use a clean cloth doused with oil to coat my punches and dies before wrapping and stowing them. I use oil soaked Q-tips to oil the bores of the dies. This is to prevent rust during storage. I live in a humid region and this is helpful in the event that my power or air conditioner goes out. It is not recommended to use solutions containing rust inhibitor on Corbin dies and punches.

Late night learning


Had to cull these. All of the cores were not sized the same as I was adjusting the punch. This is the result of the smaller cores.


Edit 08/10/24: I reworked the culled slugs. Most were turned into 120 grain slugs. One or two were turned into 125 grain slugs.


Of all of the slugs measured, they all consistently measure .357 in diameter. This is what precision looks like.


It almost looks like I know what I’m doing. The depth of the hollow points were pretty consistent with very slight variances of at most 0.05 mm. It’s tough to get a range on the weights. I need another scale. The one I used doesn’t measure tenths or hundredths. I’ll have to grab another one this week. There were some variances in height as great as 0.19 mm. This must be corrected. I have an idea why this occurred. The cores varied in size as I was adjusting my top punch. When I went to swage the ogive, some of the cores were too short to form properly along with the taller and more consistent slugs with a proper ogive and tip formation.


I’m about half as happy as I was rounding the bases during puberty. It’s starting to feel like I’m getting my money’s worth.

The scale I tried weighing slugs and cores on and they weighed 8 grams before and after. I don't think I took any before photos. 8 grams = approx 123.459 grains. Obviously these slugs weighed over 8 grams before swaging. 8.3 grams = 128.089 grains. Maybe 8.2 - 8.4 grams was the actual core weight range.


I grabbed another scale after throwing two away that stopped working. It's a cheapo that some tall redhead sold me at a head shop. I'm not sure sure how consistent it will be, but it came with a calibration weight and I have a set to test against it. 8.1 grams = approx 125.002 grains.

The greatest weight variance was maybe 1.3-1.5 grains. I don't think it will take long to get that under control. As long as I can get all of my slugs within 0.3 of a grain, I'll be happy. Does that seem reasonable?
I’ll make it a point to post the steps to setting up the press tomorrow.

Ca_Varminter said:

My Sweet-Spot for raw cores is 2 to 3 grains heavier...
I like to make sure There is Enough Excess lead to eject out the bleed port.
I have heard that if you cut to close.. Not enough lead is extruded out the port
This can cause the Bleed Port to Plug-Up!!

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@Ca_Varminter weighed mine loosely 3 grains over weight, but my scale isn’t precise. The before and after weights were the same which was around 123 grains. Grabbed a scale so I’ll get a better weight later.

Airgun-hobbyist said:

Keep this culls and press adjust their weights to match each other, even if going down 10 grains or more. Shot together, they'll likely shoot the same group size.

The single longer slug in the center is the moa accurate 155 grain, next to the shorter 140 grain culls that I will be testing out for groups.

View attachment 486814

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@Airgun-hobbyist Thanks for the tip. I’d planned to re-swage them. I’m just not quite sure if I’m limited on shape or size. I obviously don’t want to drop too much weight.

Thanks to all who are contributing to the thread.

woogie_man said:

Would be interesting if Corbin made a die that would accept the bleed offs and press them into a core that can be used for a slug.

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@woogie_man As I stated before, I think it's best to use solid lead cores to swage. All that I have read in the Corbin literature suggests this. However, they do offer core molds where you can melt the lead flakes and sprue and cast them into cores. I've seen videos of guys swaging with cast cores in the S Press as well. Here's a link to the core mold. You just have to determine which size mold you need. I've also seen videos where folks have made their own core molds. Just as long as it produces solid lead cores that can be cut is what I think is important. https://www.corbins.com/shop/corbin-core-mold-516?page=4#attr=448

I added a diagram of the front view of the press to the beginning of the first post. If anyone has any suggestions or corrections please let me know. Not being able to find a labeled diagram of the press was driving me crazy when I was reading about swaging before I got a press. Coming across new terminology with no context can be daunting when you don't know what all of the parts and components are.