Quote Originally Posted by cdmiller View Post
I’ve only handled one a couple of times. How do you tell manufacture date on one?
I can't tell you anything about manufacturer date, but I can help you visually inspect a rifle to help you know what generation the parts are on the specific model you're considering buying.

So, there appears to have been a evolutionary upgrade cycle with these. Everything from the pistol buffer tube used on the pistol versions, to pistons, to the carrier group have evolved.

You can easily see what generation the bolt carrier group is in a couple of ways:

1. Look at the firing pin retention pin in the carrier. You can see this if the ejection port cover is open. If it's split, like the cotter pin on an AR15, it's the old carrier assembly. If it's solid, it's the new captive, solid pin that the new carrier group uses.

2. Retract the charging handle and look at the bolt lugs through the ejection port. The old bolt uses squared lugs just like an AR15. The 2nd Gen bolt has rounded lugs like a KAC SR-15. The Virtus-type bolt (only compatible with the new Virtus barrels) is also rounded, but the back faces of the bolt lugs are angled toward the bolt face instead of parallel with it.

The MCX vs Virtus barrel is easy:

The original MCX barrels have the gas block at roughly 5" from the receiver and are close to a pencil barrel profile. The Virtus barrel's gas block will be much closer to a carbine-length gas block position on an AR15 and will be noticable thicker than pencil profile toward the receiver.