Mossberg 940 JM Pro Semi Auto Shotgun Review

Mossberg's new 940 JM Pro is one fast race gun.

April 03, 2020 By Chris Cerino

There have been shotguns made for almost every need. I suggest “almost” because as long as the scattergun has been around, it has been customized to meet specialized needs. Engineers at O.F. Mossberg & Sons have created another shotgun that’s certain to catch the eye of more than one crowd. If you’ve pined over the idea of an over-the-counter “shotty” to meet your 3-Gun needs, the Mossberg 940 JM Pro may be the one.

From woods and waters, to law enforcement and home defense, shotguns still play a considerable role in the world of firearms. There is no doubt in my mind as a former Special Weapons and Tactics (SWAT) operator, that shotguns are a frontrunner in the application of force. From the most violent suspects to breaching doors, shotguns get the job done, sometimes solely by intimidation. Then there are all of the competitive disciplines. Shotguns will never become obsolete.

It was sometime in late 2018 when I became aware of Mossberg’s pursuit to make an out-of-the-box, 3-Gun-ready shotgun — a complete system that fixes anything that came up short on their 930 JM Pro Series. This was much anticipated news, as I happen to be the owner of more than one imperfect 930. The news was made only more interesting by the fact that the “First Family of Shooting,” Jerry Miculek’s family, would be involved.

The Mossberg 940 JM Pro is based on what Jerry and Lena Miculek felt was necessary to make the 930 appropriate for 3-Gun competition. (Photo by Alfredo Rico)

A 3-Gun shooter myself, I’ve tried to fashion a cost effective, reliable shotgun to meet my competitive needs, but I ended up angry, frustrated and relieved of hard-earned money. The modifications necessary to bring the 930 JM Pro up to speed, as well as the constant maintenance to create necessary reliability, made me wonder if it would ever happen.

Trying to make a sporting or field gun meet the demands of 3-Gun is costly and requires technical knowledge. Extended magazine tubes for capacity; enlarged controls to ease operation under stress; accurizing for long-range slug engagements; and the potentially disastrous cutting away of receiver material for specialized loading techniques are all mandatory for making a field gun a 3-Gun shotgun. Mossberg attempted this with the 930 JM Pro, but it didn’t meet some of those requirements. Also, there’s the issue of fit. Length of pull, drop at the comb, and cast are not easily changed on many shotguns, especially those with composite stocks. Enter the Mossberg 940 JM Pro.

If, like me, you’ve longed for an over-the-counter, 3-Gun-ready shotgun, long no more. The newest addition to Mossberg’s shotgun line is not what the 930 JM Pro was. More than simply bearing Jerry Miculek’s initials, the new 940 action is a detailed, ground-up build that’s sure to impress you and your wallet.

Gun School

Mossberg introduced the replacement of the 930 series at the Gunsite Academy (gunsite.com). The 940 JM Pro combines Miculek’s genius and ingenuity with appropriate factory installed accessories, engineering and value. Mossberg Engineer John Raciti was pleased to tell those of us in attendance, “We are proud to offer a complete solution when it comes to providing a 3-Gun-ready semiauto shotgun right out-of-the-box. This is the first shotgun produced that can be quad-loaded out-of-the-box.”

He was right. I can’t find a mass-produced shotgun capable of quad-loading straight from the box. 3-Gun ready, though? We’ll see.

Joining us at the Gunsite Academy were both Lena Miculek and her always pleasant father Jerry, smiling as they passed out the new shotguns to reviewers. The differences between the 930 JM Pro and 940 JM Pro were immediately visible. Lena even brought Load-2 and Load-4 shell holders for us to use on the range. First, we learned what makes the 940 different from its predecessor, and I can say that it’s much more than gold-tone appearances. (In fact, it also comes in all-black.)

Presented to us was a dressed-up model with a gray-toned anodized aluminum receiver and gold-anodized accents. Either version, the gray or the black, sports a newly designed 24-inch vent-rib barrel with a HiViz fiber-optic front sight for rapid sight picture. Having a bright sight up front makes a difference when shooting fast by helping the shooter put the picture together quickly. If you don’t like the color, change it. Additional light tubes are included in a variety of colors. If you’re inclined, the receiver is drilled and tapped to mount a rail for your optic of choice.

External improvements don’t stop there. From the black, extended Briley choke tubes — the 940 JM Pro comes with three — to the fully adjustable competition-ready stock, there’s much to appreciate. For example, the machined and beveled feeding port was designed for any style of loading, but it is especially useful for quad-loading. Also, notable is the slimmed down forend with its improved feel and ergonomics.

Obvious 940 JM Pro accessories include the oversized charging handle and bolt release for effortless manipulation. Both are as functional as they are good looking. It may not seem like much, but having the bolt release done at the factory saves a lot of the time and frustration in trying to drill and tap that little button perfectly. Closing the bolt quickly after reloading is the benefit.

Capacity isn’t just a concern for 3-Gun, but a concern for snow goose hunters and anyone who wants the added capacity. The extended magazine is a two-piece system fashioned together at the fore-grip nut. The 940 JM Pro holds nine-plus-one rounds, the perfect number for shooting in the Tactical Optics division of 3-Gun. Also notable is that the steel portion of the magazine tube connected to the receiver is coated in boron nitride (BN). If you know anything about gas-operated shotguns, you’ll know that this can be a hard part to clean. BN keeps carbon from bonding to the metal.

The Mossberg 940 JM Pro’s loading port is factory enlarged and beveled specifically for quad-loading with either a strong or weak hand. Even if you don’t quad-load, rest assured that shucking two shells is really fast, and if you still load a shotgun one shell at a time, the shell lifter (i.e., elevator) has been modified to make it longer. This alleviates the dreaded thumb pinch or thumb-nail cut when there’s just enough room for your thumb to get stuck between the elevator and the receiver.

Shotguns work best when they fit the shooter. The 930 version had the ability to adjust the drop at the comb. The new 940 has adjustability for this, as well as cast on and off and length of pull. Maximizing performance through proper fit requires a modern system or an expensive and experienced craftsman. Proper stock fit helps in shooting more comfortably and alleviates getting a beat-up cheek bone from hard-recoiling slugs.

Internally, the hard, smooth finish of BN graces many of the critical components including the magazine tube, gas piston, gas ring, hammer and sear. Ease of cleaning is a secondary benefit of the coating. Having it on the parts of the 940’s redesigned gas system ensures reliability.

Some visible changes and other non-visible changes have been made to the gas operation. Having enlarged gas ports allows reliable use with 1-ounce shot loads and 7⁄8-ounce low-recoiling slugs, vital to 3-Gunners and recoil-sensitive shooters. The previous steel spacer tube is replaced with a corrugated, perforated and anodized aluminum spacer. According to Miculek, the new sleeve “provides relief for gasses and debris movement.” The redesigned gas piston redirects hot gasses away from the magazine tube keeping it cleaner. The single piston ring is designed to prevent seizing and is easier to remove for cleaning. Supposedly, the design changes to the gas system means cleaning is required less often.

Fouling of the gas system was a big problem with the outgoing 930. Mossberg says the new self-cleaning piston may allow firing of up to 1,500 rounds between cleanings. I don’t know that I’d chance it, but those predictions will surely get you through a match or two before you need to get down and dirty. In the words of Mossberg, the 940 JM Pro is “completely redesigned for fast-paced, reliable cycling in all environmental conditions.”

On the range, there were 20 or more guns. After a quick safety briefing, Gunsite instructors allowed Team Miculek to take the lead. Jerry started off with information about cyclic rates and load preference, and after a quick lesson on how to hold the gun to make it do your bidding, Jerry let it rip. I don’t know that he’s capable of firing a single shot, and I suppose doing so would be anticlimactic. What he does do is fire pairs. Jerry shoots pairs so fast you’d swear he’d only fired one shot. He demonstrated that the 940 will cycle as fast as you can fire.

After some showmanship from Jerry, Lena got us on line with our guns. First, we practiced with the new quad-loaders provided by King Competition (kingcompetitionproducts.com). Lena allowed us to choose between two or four shells at a time based on our ability. I chose to load four. The crisp 5-pound trigger was clean and quick to reset. Our drill was to shoot two, load two and get back on target as fast as possible. The guns ran well with a mixture of 1-ounce and 11⁄8-ounce loads.

After close-in work and loading, we moved to using slugs. Being optimized to the Miculek slug preference, it was obvious the 940 is a 7⁄8-ounce slug slinger. At 50 yards, firing the low-recoil slugs was the equivalent of plinking with a pistol-caliber carbine. Higher powered, 1,600 feet-per-second (fps) slugs of the 1-ounce variety printed higher because of their speed. Burying the HiViz front sight was the fix to get hits. For Gunsite’s Safari Scrambler, we only fired the 1,600-fps slugs. Obtaining hits out to 125 yards was simple when I buried the front sight low. With three misses on 14 targets, I figure I could get them all with 7⁄8-ounce slugs. Gunsite made a great venue for shotgun training. I only wish we had more time.

Mossberg taking another bite at the 3-Gun-shotgun apple is cause for other manufacturers to start rethinking their products. For those people who’ve been wanting to try the 3-Gun game, but haven’t because of the shotgun component, you now have a viable option. Knowing the people behind this new shotgun, I’d say that the 940 JM Pro is worth a serious look.