Ar Upper Wont Fit Lower: A Comprehensive Guide
When it comes to fitting an AR upper receiver to a lower receiver, many enthusiasts encounter issues that can be quite frustrating. Whether it’s due to incorrect dimensions, manufacturing defects, or simply a poor fit, understanding the reasons behind this problem and how to address them is crucial. In this article, we will delve into the various aspects of why an AR upper might not fit a lower receiver, and provide you with practical solutions to ensure a seamless integration.
Understanding the Basics
Before we dive into the specifics, it’s important to have a basic understanding of the components involved. An AR upper receiver is the part of the firearm that houses the barrel, bolt carrier group, and other internal components. The lower receiver, on the other hand, is the part that holds the magazine, trigger, and other external components. Both receivers are designed to be compatible with each other, but sometimes, they may not fit perfectly.
Common Reasons for a Poor Fit
There are several reasons why an AR upper might not fit a lower receiver. Here are some of the most common ones:
| Reason | Description |
|---|---|
| Incorrect Dimensions | Manufacturing tolerances can lead to slight variations in dimensions, causing a poor fit. |
| Manufacturing Defects | Defects in the receivers, such as burrs or uneven surfaces, can prevent a proper fit. |
| Corrosion or Rust | Corrosion or rust can cause swelling and make it difficult to fit the receivers together. |
| Improper Cleaning | Failure to clean the receivers properly can lead to debris or gunk that prevents a good fit. |
Addressing the Issues
Now that we’ve identified the common reasons for a poor fit, let’s explore some solutions to address these issues:
1. Inspect the Receivers
Start by inspecting both the upper and lower receivers for any visible defects, such as burrs, uneven surfaces, or corrosion. Use a fine-grit sandpaper or a deburring tool to smooth out any rough edges. If there’s significant corrosion, you may need to use a wire brush or a chemical cleaner to remove it.
2. Clean the Receivers
Thoroughly clean both receivers to remove any debris, gunk, or oil. Use a solvent and a soft cloth to clean the surfaces, and then wipe them down with a dry cloth. This will help ensure a good fit and prevent future issues.
3. Use a Receiver Block
A receiver block is a tool designed to help align and hold the upper and lower receivers during assembly. By using a receiver block, you can ensure that the receivers are properly aligned and reduce the risk of a poor fit.
4. Apply Lubrication
Apply a thin layer of lubricant to the mating surfaces of the upper and lower receivers. This will help reduce friction and make it easier to fit the receivers together. Be sure to use a lubricant that is suitable for firearms, as some household lubricants can damage the receivers.
5. Seek Professional Help
If you’ve tried all the above solutions and still can’t get the upper and lower receivers to fit, it may be time to seek professional help. A gunsmith can inspect the receivers and make any necessary adjustments to ensure a proper fit.
Conclusion
Dealing with an AR upper that won’t fit a lower receiver can be a challenging task, but with the right knowledge and tools, you can overcome this issue. By understanding the common reasons for a poor fit and following the suggested solutions, you can ensure a seamless integration and enjoy a reliable firearm. Remember to always prioritize safety and seek professional help if needed.
