Our Apex uses a DPMS LR-308 pattern low profile receiver . The Alpha uses an SR-25 pattern receiver. The Vanguard uses a standard AR-15 pattern receiver. The Viper uses a standard AR-15 pattern receiver with a PCC ejection port. Due to differences in the DPMS LR-308 across manufacturers, we can only guarantee fit with the following lower receivers. Contact us with questions on your specific lower. ADR Tactical

While we would love to offer a configuration that is chambered in the .277 Fury, we cannot accept the liability issues surrounding the cartridge. SAAMI max average pressure is 65k psi for safe conventionally made firearms. The brass cased Fury cartridges operate at or below this limit. The hybrid cased ammunition, however, does not. They operate well above the safe limits of conventional rifle barrels, especially those in AR rifles.

The major limitations are on component form, fit, and function. There are, however some other specific restrictions due to supplier limitations. Examples include: - Matched headspace bolts may only be offered with specific barrels and chamberings. - Some chamber options are only available for use with adjustable gas blocks. - Some chamber options may come in limited barrel contours, lengths, and finishes. Please contact us with what you are looking for a custom upper build and we would be happy to assist you in figuring out what we can do for you.