A customer asks Will to build a quad MG 42 that he can take to a gun show that weekend. Will is hesitant given costs and timing but the customer is persistent and has the money to get the job done. Will can't say no. Meanwhile, a gun collector brings in a 19th century French Palm Pistol. Will, who has a sweet spot for historical firearms, can't help himself and buys the gun... even though it doesn't fire. Will tells Vince to fix the gun so it will fire and triple the gun's value. And a customer walks in with a right-handed AR 15, but he is left-handed shooter. He wants the action of the gun changed to fit his left-handed needs. Of course, Will and his team are just the guys to get all this done.

The Red Jacket crew tackles the nearly impossible - taking a fully automatic Mk 19 Grenade Launcher, and converting it into a silenced, single shot select fire weapon. Meanwhile, Kris tries to make a hunting rifle float for a customer, while Will builds a version of a knife that shoots.

Will brainstorms combining a shotgun and a taser for the police, but someone in the shop will need to be tased for the demonstration. The Red Jacket team revives a demilitarized WWII-era anti-tank gun to honor a veteran, while Will lays down the law for Kris who needs to back off on the front office flirting.

Things get crazy when Will tackles a WWII-era 57mm cannon. Meanwhile, Vince gives an AR-15 the Red Jacket treatment for Super Bowl champion and New Orleans Saints kicker Garret Hartley. Then, things between Kris and Stephanie take an unexpected turn.

The Red Jacket crew creates a dual mounted M240 Bravo machine gun and Mark19 grenade launcher for the local sheriff's Gulf Patrol Boat. Will restores a WWII German Luger after he's inspired by the gun's great battlefield capture story. And Kris finally steels himself to respond to Will's ultimatum — does he choose Steph or Red Jacket?

Will and the Red Jacket crew resurrect an 82mm Russian mortar, and push its limits going HE - high explosive - while testing. Then, tempers flare when Kris has trouble building the new, RJ Desert AR. Also Ted Nugent stops by for some belt fed, full auto madness.

In this explosive season finale, Will, Steph and Kris head to Vegas to demo the Red Jacket Desert AR - an American gun built to challenge the AK during all-conditions desert warfare. Then, everyone is stunned when Red Jacket loses a valued member.

Jon Weiler of Professional Marksmen Inc. commissions the Red Jacket crew to integrally suppress a .50 caliber sniper rifle. This is one of the largest caliber gun rounds — and gun — in the world. And they only have a week to do it. Will, Joe, and Kris work through the night to come up with a plan.

Vahan Kelerchian from Armament Services International has a client willing to pay $50,000 to get his Japanese auto cannon repaired — but he needs Will's help. Will tells him he is backed up and can't do the job for months. Vahan leaves an unhappy customer. Joe, who recently lost his second job teaching, sees the situation unfold and decides to take on the job himself — and enlists the help of the other RJ guys. Everyone is nervous but they are willing to do it for Joe.

Jesse James surprises the crew at Red Jacket Firearms as he stops by the shop to have them build a custom WWII BAR machine gun for him. He wants to help with the build, and had been talking to Vince about the weapon. Jesse wants Vince to lead the build. Tension builds with Vince in the shop again.

Red Jacket is put to the test when a 70-year-old, $150K, full auto 40mm Bofors cannon, with over 500 parts, breaks down 4 days prior to its sale. Also, the crew resurrects an 1855 Volcanic Pistol. Then, a rockin'.38 Special's secret markings reveal its royal lineage.

Red Jacket Firearms redefines armored cars when they conceal fully automatic M-16s and Claymore mines in an armored Porsche for a client that needs protection as well as the ability to fight back. Meanwhile, Steph goes rogue and builds a custom AR behind Will's back. And Jesse James returns to Red Jacket with his engraved BAR parts. The team assembles his gun and together they take it to the range where Jesse fires the custom-built weapon.

Max Brooks, best-selling author of The Zombie Survival Guide and World War Z, drops by Red Jacket Firearms to discuss the ultimate zombie gun. Max wants to use a .22, but Will wants to use an M16. RJF divides into two teams: Team Max and Team Will. Team Max builds with the civilian in mind – small and lightweight, with plentiful ammo. Team Will builds with the military in mind – big bangs and full auto mass destruction. Both guns are put to the test when the teams meet up in the woods for a nighttime zombie apocalypse shootout. And while Will and team are knee-deep in their zombie gun builds, a Lewis Gun – a World War I–era machine gun – comes into the shop for repair. Will tasks Steph with the project. She knows this is a test to see if she can fix it – and she’s up for the challenge.

The Red Jacket crew bring an antique, blackpowder Lyle Cannon back to life for Aerosmith rocker Joe Perry. But one cannon is never enough. Kris and Flem repair and then square off to prove whose WW2 cannon is better: a German PAK 36 or an American 57mm.

An avalanche expert challenges Red Jacket to build a gun that saves lives. Will agrees to reactivate a 57mm recoilless rifle for a mountain rescue team in the Pacific Northwest. Kris must build a mountain of snow in the bayou to test out the gun!

The Red Jacket team attempts to un-bust a busted myth from Mythbusters. Tory Belleci and Kari Byron come out to Louisiana to help the team break the famous James Bond myth. Will Red Jacket be able to blow up a propane tank with a single gunshot?

A Benelli M4 shotgun is redesigned for competition shooting.

When two clients order 3-gun competition sets for their dads, Kris decides to secretly make a third set to honor Will. The gunsmiths agree to the overtime, but late nights lead to rookie mistakes that embarrass Will when he test fires before the client.

Someone from Red Jacket must jump out of a helicopter after a special services contractor asks the team to build a tight quarters Para-shotgun. As things get hot, Will takes a call that may change Red Jacket forever...

A hurricane isn’t the only thing brewing in this season's premiere. A blacklisted visitor shows up mid storm. An important order's mishandling wreaks havoc on the shop; meanwhile the largest weapon in Red Jacket history may also prove to be the most problematic.

With the SOCOM order still on hold Will is on edge so he decides to clean house. He builds a hybrid gun out of Red Jacket spare parts. Will keeps the boys busy on an R & D project, and has an explosive confrontation with Vince.

Flem modifies an MK-7 for a sub-machine gun champ’s upcoming competition. In the meantime, desperate for revenue, Will agrees to overhaul a rusted out anti-tank cannon. Tempers flare between Joe and Kris as the missing SOCOM barrels put everyone on edge.

Money is tight, Red Jacket has gone into the red and cutting down on OT causes tempers to flare. Steph brings in the Olympic shooting team to make a commemorative gun. Will has the crew build an MG-34 for two clients in order to keep the doors open.

In an exciting challenge the crew modifies a PKM from a three man to a one-man combat unit. Will restores a Lefever rifle destroyed in a tornado. Kris makes a deal hoping he'll save Red Jacket but when Will gets bad news, he's ready to close RJF forever.

As the SOCOM order finally gets completed, Tom's unpredictable ways put his job on the line. Will and Flem have a heart to heart about his future at RJF. The crew is challenged when a client brings in an Oerlikon that sent him to the hospital once before.