The choice to buy a marine magnum is a diffcult one. It is a “niche” weapon in its stock form and while easy to modify, it can suffer from over modification. My 870 MM came from my local dealer brand new for $348.95. The first thing you notice when you open the box is the brilliant silver color of the matte nickel finish. It is coated inside and out with this finish that is extremely durable. The stock and forearm are black synthetic and while slightly ugly, they are well made and utilitarian. The barrel is 18″ long and makes for a short, handy weapon.
The gun was dissasembled, cleaned and inspected for flaws or damage. None was found. The gun comes with a factory magazine extension in matching finish that had to be installed before its first use. It replaces the magazine cap and has a brace that clamps to the barrel. It also comes with a replacement magazine spring.
Once the gun was ready to go I assembled the testing ammunition. The gun had a cylinder choke and can therefore shoot any 2 3/4″ or 3″ shells, including slugs, buckshot and steel. I procured the following types of ammunition for the tests:
Winchester 2 3/4″ steel and lead field loads for hunting
Winchester 2 3/4″ 00 buckshot
Winchester 2 3/4″ 1oz. rifled slugs
Fiocchi 2 3/4″ #4 buckshot
Federal 2 3/4″ #8 target loads
Remington 2 3/4″ STS preimer trap loads
Fiocchi 3″ magnum steel geese loads
Federal 3″ super steel duck loads
Winchester 3″ Super X magnum steel loads
Brenneke 3″ Super slam 1 1/8 oz. slug loads
Federal 3″ tactical slug load
These test were conducted over the span of a week of nice weather this past summer. Temps were in the 80’s and wind was negligible. Tests were conducted at several different shooting areas including the local public range, a public hunting area and a private shooting range I was allowed to use.
All hunting loads were patterned at 20 and 40 yards. Most loads patterned about 24″ at 20 yards and 35-40″ at 40 yards. This is a typical spread for a cylinder choke and i don’t reccomend doing any shooting beyond the 40 yard mark unless you are using slugs. Recoil with most of the hunting loads was acceptable but some of the 3″ magnum steel loads (most notably the Fiocchi geese loads left me with large bruises on my shoulder) were quite painful. The synthetic stock is hollow and makes the weapon lighter than its wood stocked counterpart, thus increasing the felt recoil of the weapon.
Slugs were shot out of the gun at 50 yard targets, 24″ in diameter. Almost all the slugs shot 3-4″ groups with the only notables being Brenneke 3″ super slam grouping at 2.25″ and federal 3″ tactical grouping at 7.5 inches. The recoil from all the 3″ slugs was significant but not painful. The 2 3/4″ slugs recoiled no more than regular shot loads.
Buckshot loads were pattered at the same distances and gave the same results as hunting loads.
At this point i stopped shooting for the day and returned home. I cleaned and oiled the gun for the next tests. The second set of shots were at the local trap range and all shootinig was #8 target loads from Winchester, Reminton and Federal. I was unable to purchase any Fiocchi target loads for these tests. All shooting was done from the 16 yard line and followed all rules of the trap club. This gun proved a dismal failure at shooting clays. When the gun is pointed up for “tall” birds the stock tends to bite your cheek badly. I borrowed some slip tape from another competetor and applied it to the stock.. This helped some but not alot. The shot pattern was not dense enough to break about 1/2 of the targets though the majority of them were chipped (chipped targets don’t count as broken). I expended about 400 rounds shooting trap and quit for the day. I had a bad bruise on my cheekbone from stock bite. The only notable failure was a “blooper” federal round. The shot and wad never left the barrel and had to be pushed out with a dowel. This was the only failure up to this point and it was decided to be an ammunition failure.
The next set of tests were conducted at a private range. I had acquired severla stock and grip options i wanted to experiment with. I purchased a Advanced technology pistol grip set with front and rear pistol grips and alos a Knoxx COPSTOCK and and ATI over reciever folding stock. I installed both pistol grips and Found while the weapon was “cool” looking, the grips made it harder to aim and handle. I shot a tactical course with IDPA paladin targets set up in different locations. The weapon bounced around badly from the recoil and i had several “short stroke” jams. After i finished the course of fire i removed the front pistol grip and reinstalled the facotry forend. This improved the weapons ergonomics markedly. While recoil was still heavy, the factory forend made the gun faster on second shots and target acquisition. I installed the Knoxx COPSTOCK and fired a few test rounds. After the fifth shot the stock cracked near the hinge point and a chip of plastic cut my cheek. I immedialty removed the stock from testing and returned it to the company. Later discussions with the company revelaed there was a wide recall on these stocks and mine had “slipped through the cracks”. While Knoxx replaced the stock free of charge, their customer service was lacking in profiency and quality. I DO NOT reccomend any of their products. The ATI folding stock also proved a failure. It fit and functioned perfectly but had more cheek bite than the factory stock. it was improved by grinding part of the plastic stock edge away and covering it with a foam cheek pad. This made the weapon comfortable to shoot but made it difficult to fold correctly. At this point i reinstalled the factory stock and forend and left them in place for the remainder of the testing. I do not reccomend the use of pistol grips or folding stocks on the 870 MM. My wrist and hand were sore for several days after the tests from heavy recoil. Many like the “cool” factor of the grips but in the real world, their constant use could result in carpal tunnel sysndrom or other hand and arm injury.
The field tests were held at the same range as the stock and grip tests were held. This range abutted a large, wooded area that held large numbers of rabbits, squirrels, and other small game. After aquiring the proper licenses, the owner allowed me to hunt in this area. The gun proved reliable and easy to handle in a real hunting situation. All shots were taken at 25 yards or less using #4 shot. I bagged my limit that day and the next. No failures of any kind were noted on this hunt.
Overall the 870 marine magnum is a well built, reliable firearm. The only complaint i have is with 3″ shells recoil becomes a problem and the gun is not suited AT ALL for shooting clay targets. Against small game at short range this gun is the perfect all-weather hunter. Its short overall length and ease of use make it an excellent choice for home defense as well.
