Building your first AR-15 is an exciting milestone for firearm enthusiasts, but it’s also a journey filled with potential missteps. While assembling your rifle from scratch can be highly rewarding, mistakes in planning, assembly, or part selection can lead to frustration or, worse, a poorly functioning firearm. Let’s break down the ten most common mistakes people make when building their first AR-15, so you can avoid them and build a rifle you’ll love and trust.
1. Failing to Plan the Build

The biggest mistake many first-time builders make is jumping into the process without a clear plan. What role do you want your AR-15 to serve? Will it be a lightweight rifle for home defense, a precision long-range platform, or a budget-friendly all-purpose firearm? Define your purpose and budget first. Without this roadmap, you risk overspending on unnecessary parts or creating a mismatched rifle that doesn’t meet your needs.
2. Cheaping Out on the Barrel and Bolt Carrier Group

The barrel and bolt carrier group (BCG) are the heart of your AR-15, handling the brunt of wear and tear. Opting for subpar components in these areas can result in unreliable performance or faster wear. Look for barrels and BCGs that have been high-pressure tested (HPT) and magnetic particle inspected (MPI) for quality assurance. Investing in these critical parts will pay off with better accuracy, longevity, and reliability.
3. Spending Too Much on Low-Impact Parts

It’s easy to get caught up in flashy upgrades like engraved lower receivers or skeletonized parts, but these add little to the rifle’s functionality. Keep your spending proportional to the rifle’s performance needs. For example, there’s no need to spend more than $100 on a lower receiver unless you’re after specific features like a threaded bolt catch or integrated trigger guard. Focus your budget where it matters most – on the components that directly affect reliability and accuracy.
4. Using the Wrong Tools

Building an AR-15 requires specific tools for a smooth and damage-free assembly. Skimping on proper tools, like roll pin punches, vice blocks, and torque wrenches, can lead to frustration, scratched parts, or even broken receivers. Invest in a basic toolset designed for AR-15 assembly, and you’ll save yourself a lot of hassle and ensure your build is completed correctly.
5. Ignoring Proper Headspace Checks

If you’re assembling the upper receiver yourself, don’t overlook the importance of checking headspace with go/no-go gauges. Improper headspace can cause serious safety issues, including misfires or even catastrophic failure. While many pre-assembled uppers are headspaced correctly at the factory, it’s still worth double-checking for peace of mind, especially if you’re using mismatched barrels and BCGs.
6. Not Cleaning or Maintaining the Rifle Properly

Even after building the perfect rifle, neglecting regular cleaning can lead to reliability issues. AR-15s, particularly direct impingement models, are notorious for accumulating carbon buildup in the chamber and bolt carrier group. Cleaning these areas after every range session is essential to maintaining your rifle’s performance. Use specialized tools like chamber brushes and bore snakes to keep everything in top shape.
7. Overspending on Aesthetics

Looks matter to some degree, but focusing too much on the appearance of your rifle can lead to overspending on parts that don’t enhance performance. For instance, choosing an expensive handguard for its aesthetics instead of its weight or modularity might leave you with a rifle that’s heavier or less practical. Function should always take precedence over form, especially for your first build.
8. Cutting Corners on Small Parts

Detents, springs, and pins may seem insignificant, but they’re critical to your rifle’s functionality. Cheap or incorrectly sized small parts can cause malfunctions, from a failing safety selector to a misaligned takedown pin. Stick to reliable lower parts kits from reputable manufacturers to avoid these headaches.
9. Underestimating the Importance of Shooting Practice

After finishing their build, many people take their AR-15 to the range once or twice and then let it sit unused. This is a mistake. Shooting is a perishable skill, and regularly practicing with your rifle will ensure you’re familiar with its operation, recoil, and sights. Plus, regular use will help you identify any issues with your build before they become critical.
10. Settling for Parts You Don’t Really Want

Sometimes budget constraints or impatience lead to settling for parts that aren’t exactly what you want. While it’s tempting to save a few bucks or buy what’s immediately available, this can lead to dissatisfaction down the road. If you’ve got your eye on a higher-quality component, like a premium trigger or bolt carrier group, it’s worth waiting until you can afford it rather than rushing the build with something inferior.
A Learning Experience

Building an AR-15 is a hands-on learning experience, and mistakes are part of the process. However, by planning ahead, investing in quality components, using the right tools, and prioritizing practice, you can create a rifle that’s both reliable and tailored to your needs. Avoid these common pitfalls, and your first AR-15 build is sure to be a rewarding success.
Have You Compromised on Components?

What specific role do you envision your AR-15 playing in your collection, and how does that influence the parts and features you prioritize? Have you ever compromised on a component for budget reasons? If so, did it affect your satisfaction with the build or its performance over time? How much do aesthetics factor into your decision-making process when selecting parts? Do you think form should follow function, or vice versa?

Growing up in the Pacific Northwest, John developed a love for the great outdoors early on. With years of experience as a wilderness guide, he’s navigated rugged terrains and unpredictable weather patterns. John is also an avid hunter and fisherman who believes in sustainable living. His focus on practical survival skills, from building shelters to purifying water, reflects his passion for preparedness. When he’s not out in the wild, you can find him sharing his knowledge through writing, hoping to inspire others to embrace self-reliance.