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The injection gun is where product meets the job. Colt builds one from a bare block to field-ready in front of the class — every nipple, valve, fitting, and injector — then covers the operating discipline and the cleaning ritual that keep it alive. Specs cross-checked against the MixMaster Pro User Manual v7.0.
After this module, you'll be able to assemble and tear down the MixMaster Pro from a bare block, apply the Teflon rule correctly (pipe threads yes, JIC flares no), run the valves with proper discipline, tune injectors for output and cold weather, execute the end-of-day cleaning that protects the block, and diagnose the common failures from the manual's own troubleshooting table.
The MixMaster Pro is Alchatek's plural-component injection gun — the tool at the end of the heated hoses for slab lifting and Deep Lock work. A and B resin meet inside its mixing chamber, which means the gun lives its whole life one missed flush away from becoming a paperweight. That's why this session exists.
Those numbers are from the User Manual, and the last two are why the Safety module's rules follow this gun everywhere: fluid injection injuries can happen at as little as 100 PSI, and reacting foam in a large mass makes enough heat to auto-ignite. Goggles always; never point it at anyone.
The gun block comes in aluminum (light, inexpensive, soft — never overtighten) and stainless steel (more solid, same care). Colt's format for the session: build one by hand, from a bare block, in front of everyone.
Every port on the block has one job. Learn the map and assembly stops being mysterious:
Assembly starts at the back: straight nipples thread into the block, converting its threads to accept the A and B ball valves — the on/off controls for each resin.
"The ball valves, they are a consumable. They're probably the primary consumable on this thing. You're gonna change them out frequently."— Colt, Alchatek Technical Training
What kills them: ISO working its way behind the white nylon seal inside the valve and tearing it, which lets material bypass a "closed" valve. Weekly-to-biweekly replacement is normal; consistent cleaning is what gets you to the long end of that range. (One more seal-killer from the manual: never soak ball valves in AP Soak 130 — the soak chemical itself damages the seals.)
The hoses from the proportioner land on JIC swivel fittings, and the sizing is the safety system: #5 JIC for the Iso (A) side, #6 JIC for the Poly (B) side. The two sizes physically cannot cross-connect — it is impossible to put the A hose on the B port. Both PMC and Graco heated hoses match these fittings.
The flush side of the gun is its own little plumbing project, and it's the part that keeps mixed foam from curing in the block:
The front rebuilds in minutes: hex plugs back in, the mix chamber (lifting tip) threads into the center, and the injectors — the metering orifices — seat into their side ports. Three sizes:
Two connection options at the tip: the 3/8" hammer-in port spins onto the mix chamber (the manual's trick: chuck the port in a cordless drill and spin it on — the threads cut into the nylon), or the button head coupler for galvanized Deep Lock tubing.
"When you open up these valves, they're all the way on, or all the way off. If you go slightly in the middle... you might not have an even mixture coming out."— Colt, Alchatek Technical Training
The handle assembly is a bolt, a nut, a spacer sleeve, and four plastic washers — the washers sit on each side of the connection so the handle rotates freely instead of binding.
"The handle is kind of an optional part in my opinion. I know half the contractors I go visit have removed the handle. It's not even there."— Colt, Alchatek Technical Training
Why crews pull it: it gets in the way working tight to concrete, and it finds your knuckles. The current machined aluminum handle is a real upgrade over the old plastic one that snapped — but whether you run one is preference, not procedure. Try both ways; keep what your hands like.
Teardown is assembly in reverse — flush lines first, then JICs, then ball valves (valves can also be serviced without full disassembly). Then the rules that protect the block:
Straight from the User Manual — the symptoms you'll actually see and the order to check things in:
| Symptom | Check, In Order |
|---|---|
| A-side pressure high | Clean the A injector → verify the A check valve works → check the wye strainers on the proportioner |
| B-side pressure high | Same sequence, B side |
| Only B discharges when valves open | Clean the A injector; confirm the A check valve is clean, working, and installed in the correct direction |
| Only A discharges | Same checks, B side |
| Material leaking past valves | Replace the valves — scarred seals from poor cleaning (or AP Soak exposure) don't recover |
| Injector won't seat fully | STOP — never force or tap. Remove it and clean the block port thoroughly with a wire brush |
| Port pulls off the mix chamber | Clean the mix chamber threads so the nylon port can bite securely |
| Water leaking from the mix chamber | Replace the flush valve and the ball-and-spring check valves |
| Output too low / too high | Swap injectors: .035 for less, .07 for more |
Source: MixMaster Pro User Manual v7.0 (rev. July 2025), Troubleshooting section.
Score at least 4 of 5 to unlock module completion.