Genesis Arms has released their Gen-12 upper and conversion kit for AR-10s. This conversion upper promises to drop on to your AR-10 lower and with Genesis mags you’ve got a 12 Gauge AR! Creating such a conversion is not an easy task. A lot has gone into creating the Genesis 12. Yes there are AR look-alike platforms out there, but the Gen-12 is an actual upper for your AR-10 DPMS Gen 1 308 pattern.
You don’t have to change buffer systems, but may want to swap magazine and bolt catches. More on that in the video below.
The Gen-12’s barrel and bolt are spring loaded. The barrel actually cycles a bit like on a Howitzer or Barret. This serves to delay opening of the action until the spring in the barrel has overcome the rearward pressure. Essentially it’s a delayed blowback operation. A major benefit of this is that the bolt carrier doesn’t need to weigh a ton to keep recoil impulses manageable. It also means that you can keep your standard Ar10 buffer and recoil spring.
Genesis Arms has a “beef up” kit that helps ensure reliable operation. The kit included a modified bolt catch and magazine catch as well as stronger springs for both. One of the unique issues of 12 gauge is that although the recoil’s peak force may not be as high as some rifle calibers it has a longer dwell time. In layman’s terms 12 gauge creates a long push instead of a short and snappy shove. This puts a different type of strain on catches.
Another challenge that Genesis has overcome is the magazine. Rimmed cartridges rarely play nicely in box magazines. That challenge has been dealt with before, but not in a magazine narrow enough to fit into an AR-10 receiver. Part of making that work meat omitting the ramp above the catch on the magazine that usually guides the receiver’s catch home on a magazine. In order to make that work the Genesis magazine catch is ramped on both sides. It is still compatible with standard AR-10 magazines so installing the Genesis catch doesn’t mean losing the ability to still use a .308 upper.
There are a lot of impressive design features built into the Gen-12 in order to keep it compatible. I’ll get it out to the range and run a variety of rounds through it to see how it fares. As you saw in the video one of the biggest challenges with shotgun ammo in box magazines is that they don’t all have the same overall length. You can buy the same load labeled as 2 3/4″ or 3″ shells from three different manufacturers and have three different actual overall lengths. Shotgun ammunition makers haven’t had to worry about it in the past because a tube-magazine fed shotgun can’t tell the difference.
For more information about the Gen-12 and Genesis Arms check out their website here.