After waiting 11 months, I finally received one of these shotguns from my distributor. It’s the model with the full-length pistol grip stock, Mossberg’s number 85370. I’ll be adding to this as I learn more about this shotgun but thought others might benefit from what I’ve picked up so far.

As received, the forend is slightly loose, as is the magazine extension. Some people on internet forums have installed a Scattergun Technologies (Wilson Combat) sling mounting plate between the magazine extension and the forend to remove the excess space and thus tighten up the forend. That works. The mounting plate for a Remington 870 is the correct fit, and the plate has a detent ball staked into the plate since a Remington needs a detent ball to secure the magazine end cap. Others are drilling a hole into the Mossberg’s forend for the detent ball. Instead, look at the plate and note which side Wilson Combat staked the ball in place, then turn the plate over and just drive the ball out with a punch since it’s not needed. Remove the magazine extension – note that the spring is incredibly long inside the tube – drop the plate in place – reinstall the extension and tighten the extension in place by hand. At this point, the excess play will be removed from the forend. The sling plate takes a 1 ¼” sling. Mossberg doesn’t include a rear swivel with the gun, so you’ll need a sling and one swivel if you’re adding a sling. And, Blackhawk’s big tactical sling that holds 15 rounds of ammo will not fit – the clips on the sling are too big to go through the swivel mounting hole in the buttstock (and that’s too much weight on a sling anyway).

To keep the magazine extension in place and prevent it from moving or becoming damaged if it encounters a door frame or other object, a clamp is needed between it and the barrel. Nordic Components has determined that the Mossberg is the same dimensionally as the Remington 870 in this respect also, so any Remington 870 clamp will work. I like Nordic’s clamp as it’s the most secure I have seen, so that’s what I installed. At this point, the front of the shotgun is absolutely solid.

The stock bolt handle is about the size of a pencil eraser and has several deep slots cut in it, making it adequate for its intended purpose. I wanted something larger so that I could reach over or under the shotgun if needed. Choate Machine and Tool makes an oversize (though not “too” oversize) bolt handle that proved to be just right. Their instructions say to just pull the stock bolt handle out. Mossberg’s manual says the same thing. You may find that pulling does not yield the desired result. At the end of the bolt handle (inside the bolt) there is a notch for a detent pin (or some such device) that holds the handle in place. Grasp the bolt handle, pull it to the rear and out in one motion. If that doesn’t work, then try forward, rear and out so that the pin is dislodged from the notch. When installing the new handle, slide it all the way in and then shake it back and forth so that the pin will catch in the notch.

The current opinion is that these shotguns need about 250 rounds to break in. That I do not know yet, but I have 250 rounds of buckshot and will add my results together with anything else I discover about these semi-automatic 12 gauge guns and report here as soon as possible.