After my tour of the POF facility yesterday, I was temporarily loaned two POF upper receiver assemblies, one of which is photographed below.

The upper assembly has a 16" fluted barrel with a carbine length gas system. It is built around the reinforced POF upper receiver and uses the POF modular rail system, which is equivalent to a 9" free float rail in terms of length.

It's remarkably light and well balanced - this rifle would have a neutral center of gravity with a lighter stock. For those of you who are not familiar with how I define various centers of gravity, and why this is important, click here. (Parts 2 and 3 are coming very soon, I promise).

It has a two position adjustable gas block - "normal" and "suppressed."

The large barrel nut functions as a heat sink, shedding heat rapidly.

The gas key has been clearanced to allow for installation of the POF Roller Cam Pin....wait a second...the gas key?

That's right, this upper has a gas tube, not an op rod!

This upper retains all the features of the POF P-415 uppers, with the important exception that it functions much like a standard AR-15. There are important differences - the gas tube is of a different design, is held in place using a dowel pin instead of a roll pin, and, of course, the gas plug regulates how much gas gets back into the action. Hence the name - Regulated Direct Impingement Kit. I'm told that it may be offered in various forms. As this is a prototype, details may change. I'll be comparing this upper to a POF op rod upper as well as standard AR-15s in the next few days.