Are there any issues matching a Spikes Tactical AR-15 lower (with Spikes lower parts kit) to a BCM M4 Upper Receiver group with 16" barrel? Both chambered 5.56 NATO.
Is there any reason to not match these up, and instead use all Spikes or all BCM parts?
That would work fine, the color might not match perfectly, but the gun would function the same as if they both came from the same company. Check out AR15.com for building advice.
