Our Product Line-up
GMI Engineering builds precision swaging tools for airgun shooters and small slug manufacturers.
Every die is machined to micron tolerances — the same tooling principles behind championship-winning competition slugs. Whether you're making your first slug or running a small production line, there's a GMI platform built for it.
Three things hold true across the entire range:
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Precision machining
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Honest value and our commitment to deliver
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Free worldwide shipping with Kits and bundles.
Not sure which platform is right for you? Compare them below, or message us your rifle and caliber and we'll point you to the right kit.
Freedom Series - Press
Freedom Press – Mark II
A production-grade swaging press, milled from solid tool steel and built to run for years.
The Freedom Press – Mark II is built for shooters and small manufacturers who need consistent, repeatable slugs at volume. It’s a ground-up redesign of our original press: a toggle-action mechanism on a solid steel chassis, running on hardened bushings and bearings with Misumi hardware throughout.
Built from solid steel.
The frame is milled from a single block of tool steel, fitted with hardened bushings and bearings, and designed to run maintenance-free. The toggle action delivers its full force at the end of the stroke — exactly where the work happens.
Built for volume.
A full swaging cycle takes two to three seconds — in practice, 8,000 to 15,000 slugs per week. The fixed depth stop in the ram doubles as the ejection mechanism, so forming and ejection happen in one continuous motion. No separate step, no wasted movement.
Every caliber, one press.
The Freedom Press accepts the full Freedom Series die range, .177 through .357 — change the die set, not the press. The adjustable, lockable punch holder sets slug length and weight, and the closed-die design forms true boat tails.
What owners say.
“Outstanding in every way. Customer service is second to none, and the slugs the dies make are flawless.” — Robert, verified owner
“Exceptionally well built, with outstanding machining and a solid, confidence-inspiring feel in use.” — Brett, verified owner
Rated 5.0 from verified buyers.
Who it’s for.
This is a serious investment for serious output. If you shoot occasionally, the SOC Kit or SlugMaster will serve you better and cost far less. If you’re producing at volume — for your own shooting or to sell — this is the tool built for it.
Only Die Sets
Precision die sets for the Freedom Press — and other presses via adapter.
Each die set is machined for the Freedom Press Mark I and Mark II and can run on other compatible presses using a GMI adapter (sold separately).
Available across all calibers .177 to .457, with adjustable grain-weight options and solid-nose or boat-tail configurations.
SlugMaster
Introducing the Slugmaster :
Affordable Precision for the High-Volume Shooter
Full swaging control on your arbor press — no dedicated press required.
The SlugMaster gives you the capabilities of a dedicated swaging press in a kit that runs on a standard arbor press.
Adjust slug weight, set hollow-point depth, and form true boat tails — all from a single die, without buying a replacement insert for every weight.
It's built around the Freedom V3 punch and pin-holder system: a closed die with auto-bleed (no trimming required), an adjustable nut that sets slug length and weight, and a depth-adjustable hollow-point pin. Available .177 to .30.
The trade-off is honest: like any hand-assembled kit, you reset the parts for each slug, so it's slower than a dedicated press. What you get in return is full adjustability — boat tails, variable weight, tunable hollow points — at a fraction of the cost of a press.
Who it's for: experienced shooters who want maximum versatility from one compact kit.
SOC Kits
SOC Kit — The Cowboy Swage Kit
The simplest, most affordable way to make your own slugs.
The SOC (Smooth Ogive Curve) Kit is our original product and
the most affordable swaging kit in the world, starting at $350.
Five parts that stack together, a standard arbor press, and you're making accurate slugs with a smooth ogive that meets the body cleanly — just like premium commercial slugs.
It's a fixed-weight kit: each die makes one slug weight. You set the nose — flat, dimple, or hollow point — by swapping pins, and adjust weight a few grains with different base punches.
Available in every caliber, .177 to .457.
Built to be simple and to last. Many of the first SOC kits from 2019 are still running today, having made millions of slugs between them.
Throw it in your bag and forget it.
Who it's for: shooters who want one reliable kit for their caliber — and the ideal starting point before stepping up to an adjustable system.
After-Market Solutions
Press-Slug Die Set
Aftermarket Die Set for Press-Slug® Press Systems
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Now Compatible with Press-Slug® Press Systems – GMI Engineering die sets can now be directly installed on Press-Slug presses with no modifications required.
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Aftermarket Precision – This is a high-quality aftermarket upgrade, not an OEM part, and not affiliated with or endorsed by Press-Slug®.
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Enhanced Accuracy & Performance – Enjoy the trusted GMI quality, performance, and consistency, now on your existing Press-Slug® setup.
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Advanced Hollow Point Tuning – Comes with a depth-adjustable hollow point pin holder for improved customization and slug balance.
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Plug & Play Installation – Designed for effortless installation; simply mount the die set and start swaging.
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⚠️ Disclaimer – GMI Engineering does not claim ownership of the Press-Slug® brand and supplies this die set exclusively as an aftermarket solution.
Drop In Kits compatible with Corbin® Press Systems
Drop-In Die Set Kit for Corbin® made
presses.
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Now Compatible with CSP1® and 2, Hydro® Press Systems – GMI Engineering die sets are precisely built to fit common swaging press platforms that use industry-standard die threading and dimensions, with no modifications required.
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Premium Drop-In Kit – This is a high-precision drop-in solution, not an OEM product, and not affiliated with or endorsed by any original manufacturer.
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Enhanced Accuracy & Performance – Experience the trusted GMI quality, consistency, and precision-engineered results on your existing swaging setup.
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Advanced Hollow Point Tuning – Features a depth-adjustable hollow point pin holder for refined control over cavity depth, weight distribution, and final projectile performance.
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Plug-and-Play Installation – Designed for effortless mounting; simply install the die set with the adapter and begin swaging immediately.
⚠️ Please Note: This Equipment is an aftermarket product developed independently by GMI Engineering. It is not an OEM part, nor is it affiliated with, endorsed by, or manufactured by Corbin®. The brand name is used strictly to indicate product compatibility. Used under Nominative Fair Use policy - Report any discrepancies if found to GMI Engineering
