Any problems with light target/low recoil loads in a 940?

[dcurtis101]

This is a novice question but my searches didn't uncover any previous threads on the subject. If there are any please point me in the right direction.
Question: In reading I've come across concerns that "some" auto loaders have issues with light/low recoil loads. Should I have this concern with a 940? I have some Winchester 1/8oz. #7.5 shot AA "light target loads" but haven't tried them yet.
Also, it's not very clear to me what classifies a load as "light" or "low-recoil". If someone could elaborate on the differences I'd appreciate it.
Thanks in advance for your help!

 

[Jmm14534]

dcurtis101,
No question is a bad question when you’re talking about firearms. Better safe than sorry.
Your Winchester AA #7.5 shot has a load of 1.125 or 11/8 oz of shot. That would be considered a “heavy” load. There are some shells that have 0.875 or 7/8 oz of shot and these would be considered “light” loads. Generally the lighter the load the lighter the recoil is but this is not the only reason one chooses the load they want. Velocity of the shot is another. The higher the load the faster the shot travels. Cheap shotgun ammo usually uses 7/8 oz. This is OK with a pump but could cause problems with a semi. The DR EQ (dram equivalent) is the amount of powder that pushes the shot. Some ammo boxes do not publish this parameter but it can be determined from velocity. If you choose ammo with a velocity of 1100 or more feet per second then you are shooting heavy loads.
A semiautomatic shotgun uses the energy from the blast to cycle the action. Some semi actions may not be 100% reliable with lighter loads. There are ways around this if it’s necessary.
My M930 Snow Goose eats anything I run thru it but it’s been pretty heavily modified. Most of these mods are already part of the M940. If your semi doesn’t like light loads then don’t use then. Get some “heavier” loads. The ones you have are OK.
There is also high brass and low brass but that’s another story.

 

[Bobster]

Adding to what Jmm said, if it is a brand new gun, sometimes there is a "break-in" period that will mate metal parts together and "clean" some of the rough edges from manufacturing. It may require a couple boxes of higher-power loads to achieve reliability. Refer to the Owner's Manual and call Mossberg if you don't have one, they will send it to you.

It is always good practice to clean and oil a new gun, just in case. I prefer to "ease-in" a new gun by filing/sanding sharp edges from stampings and other parts. Sometimes the receiver/bolt may need smoothing/polishing. Do not smooth things that are supposed to be sharp like the sear and extractor.

IMO, owning a gun is like owning a car, many questions on operation can be found in the OM. Also, if you don't know how to do minor repairs/disassembly, you shouldn't be driving/shooting one. Checking oil, fluids and tire pressures are a couple "essential" skills as are field-stripping and barrel removal with a shotgun.

 

[Jmm14534]

What Bobster said. One of the drawbacks of a semiautomatic shotgun is the disassembly, inspection and cleaning. A new shotgun absolutely needs this. Once you start shooting it the maintenance frequency will be self evident. It will go through a break in period.
I’ve attached a few photos of a complete disassembly of one of my M930 semi shotguns.
A complete tear down and thorough cleaning is at least 4 hours. Basically a football game.

 

[dcurtis101]

A wealth of great practical information. Just what I was hoping for. Thanks to you both for taking the time to reply. Much appreciated!
The Mossberg customer service folks do recommend a "break in period", which seems perfectly logical to me so parts and tolerances can loosen up a bit to work together smoothly. They say I should run some 1400 fps shells for this purpose. Didn't say how many shells constitute a break in period. In my last exchange with them, I mentioned shells with 1400 fps are to hard to find for me (1150-1250 seem to be the norm) and they replied;
"The 1400 is not a "hard line", I would stick above that point to break in tolerances then you should be fine around the 12-1300 threshold".
This seems conservative, but that's what you'd expect their position would be I guess. Hopefully the 12-1300 threshold is not a hard line either. I'm still left with trying to locate 1400 fps shells...
Good advise on maintenance. I'm familiar with maintaining semi-automatic handguns. Autoloader shotguns are new to me so I'm a bit apprehensive. I'll get over that soon enough. I've been through the manual several times and there's video by Jerry Miculek and his daughter on full maintenance. I appreciate the precision design and operation of firearms so I actually enjoy the cleaning aspect. I don't feel comfortable going at parts with a file just yet. A gunsmith I'm not.
Great pics! Thanks for sharing them. I'll have to get me one of those exploded part mats for my 940.

 

[Jmm14534]

Run some of these through it. As many as you can. Your shoulder will take a beating but all target loads will seem like a walk in the park afterwards.

 

[dcurtis101]

Thanks, I will do so. At 1600, those should definitely move.

 

[Jmm14534]

Nice. Get a half a dozen boxes of slugs and set up 2 or 3 targets at slightly different ranges and angles and do some speed shooting and reloading exercises. You can mix in some lighter target loads. It won’t hurt anything. If they result in stoppages then you will get some practice clearing the mix up and getting back into the fight. This will give you some good practice and let you see how accurate you are with the slugs at various ranges. I usually do 10, 15 and 20 yards (ie. Home defense distances). Use the target loads at the lower distances and the slugs at the longer distances. If you are a hunter then take some shots at 50 and 100 yards with the slugs and see where you are at.