What Uppers Work with DPMS Gen 1 Lower Receivers?
Finding compatible uppers for your DPMS Gen 1 lower receiver can be tricky, as there are variations in specifications across different manufacturers. This guide clarifies what you need to know to ensure a safe and functional AR-15 build.
Understanding DPMS Gen 1 Specifications:
The key to finding a compatible upper lies in understanding the unique specifications of the DPMS Gen 1 lower receiver. Unlike the more standardized Mil-Spec AR-15 lowers, DPMS Gen 1 receivers have a slightly different dimensional profile, particularly in the area where the upper receiver mates with the lower. This difference can cause compatibility issues if you're not careful. The most significant issue is the slightly oversized receiver extension (or buffer tube) opening.
Identifying Compatible Uppers:
While many uppers might seem to fit, it's critical to find one explicitly designed for DPMS Gen 1 lowers. Here's what to look for:
- Manufacturer Specifications: The most reliable way to ensure compatibility is to check the manufacturer's specifications. Look for uppers explicitly stating compatibility with DPMS Gen 1 lowers or receivers with the same dimensions. Some manufacturers might advertise "DPMS Pattern" uppers, but this doesn't guarantee compatibility with the first generation.
- "DPMS High" or "DPMS Low": You may encounter this terminology. "DPMS High" refers to uppers designed for later DPMS generation receivers, which tend to be more closely aligned with Mil-Spec. Therefore, "DPMS Low" is often used to refer to uppers designed to work with the older Gen 1 design and its specific dimensions. Look specifically for this terminology.
- Direct Observation (If Possible): If you can physically examine an upper receiver before purchasing it, carefully inspect the receiver extension opening. A slightly smaller opening is a good indicator of potential incompatibility.
Potential Issues with Incompatible Uppers:
Using an incompatible upper receiver can lead to several serious problems:
- Loose Fit: The upper and lower may not lock securely, resulting in unsafe operation. This can lead to malfunctions, and potentially dangerous issues like the bolt carrier group failing to fully cycle.
- Excessive Play: An upper with excessive play can cause parts to rub against each other, leading to premature wear and tear.
- Functional Failures: The action might not function reliably due to misalignment of critical components, resulting in jams, misfires, or even a catastrophic failure.
Where to Find Compatible Uppers:
Your best bet is to purchase both the upper and lower receiver from the same manufacturer. This helps guarantee compatibility. However, if you already have a DPMS Gen 1 lower, carefully research the upper receiver you are considering to verify its precise compatibility. Reliable online retailers often provide detailed specifications and can help you find what you need. Remember to always verify compatibility before you purchase any components.
Conclusion:
Building an AR-15 requires careful attention to detail. When using a DPMS Gen 1 lower, choosing a compatible upper receiver is critical for safety and functionality. Double-check manufacturer specifications and, if possible, examine potential uppers carefully before purchase to avoid potential problems. Remember safety is paramount when working with firearms.
