Smyth Busters: AR-15 Small Parts Kits Are NOT All the Same
In this episode of SmythBusters, Steve and Mike dive into a surprisingly important topic: Are all small parts kits for the AR-15 created equal? At first glance, it might seem like a bag of springs and pins wouldn’t matter much—but according to these two experts, that assumption couldn’t be more wrong.
What You Will Learn
By watching this video, viewers will learn why the small parts in an AR-15—like springs, detents, pins, and triggers—play a critical role in the rifle's reliability and performance. Steve and Mike explain how differences in materials, manufacturing processes, and quality control can make or break your build. Whether you're assembling a new rifle or upgrading components, this video helps you understand what to look for in a high-quality small parts kit and why cutting corners on these pieces can lead to major issues.
Benefit
Watching this video will help you avoid common pitfalls when choosing or installing small parts in your AR-15 build. You'll gain practical tips from industry experts on how to identify quality components, ensure long-term reliability, and get the best performance from your rifle—all without wasting time or money on subpar parts.
Why Small Parts Matter
Mike opens the discussion with a crucial insight: AR-15 malfunctions are often caused by the smallest, most overlooked components. When a gun fails, it's usually not the rail falling off or the barrel being out of spec—it’s a $2 spring or a subpar detent that causes the problem.
Spring Material: Not All the Same
One of the first things Mike checks is spring material. Low-grade options like 302 or 303 stainless can't be properly heat-treated, leading to shorter service life. On the other hand, materials like 17-7 stainless are heat-treatable and offer far better durability—especially important for components like hammer springs.
Triggers and Fire Control Groups
Even within mil-spec tolerances, trigger performance can vary wildly—from 5.5 lbs to 9 lbs pull weight. That’s a big spread. Quality manufacturers, including Sons of Liberty Gun Works, BCM, and PSA, refine their triggers to deliver a consistent, crisp break every time—removing the "trigger lottery" effect.
These improvements matter when it comes to reliability, reset, and consistent hammer strikes, which are essential for accurate and dependable shooting.
Material and Finish on Detents & Pins
Even tiny parts like detents and pins make a big difference. If they’re made from the wrong material (e.g., zinc-plated instead of cadmium-coated), they’ll wear out faster and possibly cause functional issues. Loose or "squishy" detents, for example, can lead to unreliable engagement in pivot and takedown pins.
High-Stress Parts: The Bolt Catch
One of the most stressed parts in the AR-15 small parts kit is the bolt catch. It has to withstand the full force of the bolt being slammed forward repeatedly. If this part isn’t made to the proper spec or treated correctly, failures are common—and dangerous. A broken bolt catch can leave debris rattling around inside your rifle.
Don’t Skimp on Quality
The price difference between top-tier small parts kits and low-quality ones is often just a few dollars. So why risk your rifle’s reliability to save a couple of bucks? Mike recommends always going with known, reputable brands that adhere to proper materials, processes, and quality control.
Final Thoughts: Quality Control Is Key
Even if the parts are made from the right material, poor QC can ruin everything. Mis-sized pins or improperly finished components can force you to use a hammer during installation—never a good sign. As Mike puts it: "If you’re fighting your parts during install, something’s wrong."
You, the builder, are the final quality control checkpoint. Lay out your parts, inspect them, and make sure everything fits as intended.
Myth: Busted ✅
So, are all AR-15 small parts kits created equal? Absolutely not. From spring material and trigger consistency to detents and bolt catches, the quality of these small components has a major impact on how your rifle performs.
If you’ve had your own experiences—good or bad—with small parts kits, let us know in the comments. And don’t forget to subscribe for more Smith Busters episodes from Brownells and Sons of Liberty Gun Works.
