Primary & Secondary Podcast · Primary & Secondary

Will Larson Armorer 2018

June 30, 2025·59 min·4 clips

Larson argues that both Kalashnikov and Stoner designed their rifles to kill people, and once shooters lose sight of that to worry about FDE color matching, 'things have gone wrong.'

1. Primary & Secondary Podcast presents a live armorer class with instructor Will Larson covering AR-15 architecture for a group of students in 2018. 2. Larson is identified as an armorer with experience at Blackwater and overseas military deployments; his co-presenter Lane and other named students (Jason, JP) participate throughout. 3. The class's core thesis is that most AR-15 buyers and even department armorers cannot identify the difference between correctly spec'd components and inferior substitutes, which has real consequences for reliability. 4. The session opens with a survey of students' personal rifles, revealing a mix of mil-spec and commercial buffer tube extensions across brands including BCM, Sons of Liberty, Hodge, and Bushmaster. 5. Larson explains that commercial buffer tube extensions require commercial-dimension stocks and warns departments that a mixed inventory means a patrol officer with a broken commercial stock will need the correct commercial replacement — not the more common mil-spec part. 6. The B5 Systems SotMod stock is discussed: LMT attempted to sue B5 over the name, but the SotMod was developed at Crane Naval Special Warfare and nobody owns that designation, the same reason multiple companies build rifles called the Mark 18. 7. The upper receiver section covers the distinction between carbine and rifle flat-top uppers and the critical difference in M4 feed ramps, which are machined into carbine uppers to complete the feed profile with the barrel extension. 8. Larson describes a case from an Arizona law enforcement agency where an armorer installed flat-top carbine uppers on 20-inch patrol rifles, creating a lip that impeded feeding and rendered the SWAT team's rifles non-functional — 'basically clubs.' 9. He demonstrates that the OEM cost difference between a correctly spec'd upper with M4 feed ramps and one without is zero — a single additional CNC programming step — and argues the problem persists because consumers keep buying deficient guns without knowing the difference. 10. Larson references the Rock River Dremel effect — armorers grinding feed ramps into incorrect uppers post-assembly — as an example of a widespread shortcut that also removes the protective anodizing from the aluminum. 11. He surveys barrel markings and forge codes to explain how to identify genuine Colt, FN, BCM, and other manufacturers' uppers versus unverifiable commercial forgings, noting that military uppers require an F stamp for FN or a C for Colt. 12. The cleaning segment challenges military doctrine: Larson describes operating guns to 2,000 rounds on a wipe-down and re-lube cycle after abandoning the solvent-tank process he learned at Blackwater, attributing the elaborate original process to institutional inertia. 13. Larson delivers a history-of-design argument: the AK-47 was developed by Kalashnikov to arm Soviet citizens for communist expansion, and the AR-10 was developed by Stoner to counter it — both were weapons platforms designed to kill, not accessories. 14. He argues that the firearm community has lost sight of the rifle's functional purpose, prioritizing FDE color matching and cosmetic customization over whether the gun reliably feeds and fires. 15. The barrel section frames the barrel and bolt carrier group as the heart and lungs of the rifle, with everything else — rails, furniture, accessories — being secondary to those two components. 16. Larson discusses CIA barrels — unidentifiable commercial barrels with no manufacturer markings — as an accountability problem: when a gas block migrates and destroys the barrel, there is no one to pursue for a warranty claim. 17. A student's rifle with a migrating gas block and gouged barrel is passed around as a physical example of what happens when barrels are not properly dimpled for set screws. 18. The class format is a live in-person armorer course with physical components being passed around the room, questions from named students, and projected slides with photographs referenced throughout. 19. Law enforcement armorers, serious AR-15 builders, and competitive shooters who want to understand component compatibility and identify quality at purchase will find the class directly applicable. 20. Casual recreational shooters focused on aesthetics or those unfamiliar with basic AR-15 nomenclature will find the technical density challenging without prior foundational knowledge.

As heard by us

A practical, close-to-the-bench discussion of why small build details shape reliability.

This episode reads like a shop-floor lesson in why rifle systems behave differently once small manufacturing details, older parts, and mixed inventories start to stack up.

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Why you'd press play

If you want a practical teardown of rifle standardization and feed-ramp differences, this one gets technical fast.

Read the full recommendation in PlayNext →

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