Why are magazines loaded from the bottom so common?

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BSA1

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I have been studying the designs of WWI and WWII small arm weapons which has provoked a thought to me.

Why are modern long guns (both military and sporting) made with magazines that are loaded from the bottom of the receiver so common?

Before you answer consider the disadvantages of the detachable magazine that fits from the bottom of the receiver.

1. A magazine that extends past the bottom of the receiver (most typically more than 5 rounds) makes shooting from prone position difficult. The gun must be held high enough off of the ground because of the length of the magazine. For a soldier this exposes him to be being seen and to enemy fire. For the hunter an awkward prone position can mean a missed shot or wounded animal.

2. The magazine can accidentally fall out of the gun only be discovered when it is needed later. Soldiers carry extra mags so it will take them longer to get their weapon working. For the hunter though it could mean the end of the hunt unless they carry a extra magazine (which of course is always a good idea).

3. Magazine changes in long guns are more difficult than with a handgun. With practice changing magazines in a pistol can be made smoothly, naturally with little time taken from looking at the target. With rifles the magazine change is more difficult. The magazine release is not easily reached by the thumb and it is not a natural movement like with handgun where it is hand touching the other hand.

There are some interesting designs that feed from the top and side of the receiver. Of course the Garand rifle is the most successful American design for loading from the top and many bolt action hunting rifles are loaded from the top.

However one of the disadvantages of bolt action rifles that load from the top also have the magazine floorplate to be opened from the bottom for easy unloading. This means the floorplate can be opened accidentally with the resulting loss of ammunition.

So what about feeding from the side of the receiver? It doesn’t interfere with the sight picture, allows for a better prone position, is easier to see the magazine well for magazine changes. One of most successful military long guns that come to mind is the British Sten gun.

Or how about an angle feed from the top of the receiver? Off set at enough of angle to allow for normal sighting. Reloading will be super easy along with be able to tell at a instant if the magazine is still in place ready for action.

A top, side and angle feed could also have a non-detachable magazine and be fed with the stripper clip.

I am trying to recall but didn’t the Japanese have a side fed rifle or submachine in WWII? I do recall they had a crew served machine gun that fed from stripper clips for the side of the receiver.

I know the AR/M-4 isn’t going away anytime soon but is this a idea worth pursuing?
 
Top load has been done, Bren machine gun, and some Japanese machine gun that fed from an open topped hopper, some Russian machineguns fed from a top mounded "pancake drum". Main problem is interference with the sights and increasing the width of the gun.

From the side is good for prone -- Stirling and Sten used it, but it makes things 3-dimensionally awkward. Same problem with bottom loading drums like the PPsH or Thompson, they work but add their own set of problems.

Been done, if there were any real advantages over the standard bottom loading detachable box magazine or top loading stripper clip designs they'd have taken over in modern designs.

If you don't want a bottom loading box mag, belt-fed seems the next best option.
 
I thought about the hopper feed but that is a crew served weapon. I am talking about individual small arms.

A lot of ideas have been tried especially in the early 20th century. With todays computer aided designs I wonder what could be designed or redesigned?
 
Aren't you overlooking the ambidextrous quality inherent in a bottom feed weapon platform? Not to mention the increased mechanical complexity involded in making something like the Calico or P90 feeding system work.
 
Keeping the weight of a magazine, and effectively, a rifle in line with the center mass of the receiver helps keep the rifle upright and not canting to one side or another. Try a rifle with a heavy optic on a cheap bipod and you'll see what im talking about. Most mags aren't long enough to cause that much of a problem. Also try falling on a mag protruding towards your chest and you will see why there aren't more rifles like that.

Sent from my LGLS740 using Tapatalk
 
I'd love to see someone make like a semi-auto closed bolt Owen clone or just something with a top feeding magazine that takes Glock 33 round "happy sticks" as it were. With a slide-fire stock adapter it could make an excellent and fully legal ersatz buzz gun.
 
Aren't you overlooking the ambidextrous quality inherent in a bottom feed weapon platform?

Good point. The magazine release on the AR/M-4 is not ambidextrous as well as guns that have push button safety on the trigger guard although I understand your point that the safety can be moved to the other side for lefties. A true ambidextrous design is the safety mounted on the top of the tang.

I will rate this point as both plus and minus.

Not to mention the increased mechanical complexity involded in making something like the Calico or P90 feeding system work

Any idea about how well the Calico system works?

A stripper feed is a simple time proven device that works well.
 
The Australians liked the top feed Owen SMG.
The Johnson LMG was side feed, just to add to the list of examples.

One advantage of the top magazine is that Gravity is working for you. The magazine spring is not having to lift the weight of the cartridges. More help in a LMG like Bren than a SMG like Owen. Neutral in a horizontal magazine.
 
A bottom feed magazine keeps the rifle in two dimensions. Length and height essential, width isn't a concern. If the magazine feeds from the side it adds the width dimension and increases the perceived bulkiness of the rifle. I prefer the more or less streamlined M4 and would really hate if it had a magazine sticking out the side.
 
For a gas operated* semi-automatic or full auto weapon you have constraints about where you can put the operating rod to cycle the action. Running the op rod on the side either requires a contorted piece of steel like the Garand, M1 Carbine, or M14, or leads to a wider rifle, like the AUG.

Most builders want to keep the bore of the rifle/MG as low as possible to reduce climb, so they put the gas system on top of the bore. That makes the top the obvious place to put the operating rod too. Since you want as slim a weapon as possible, the bottom is the next best place for the magazine. Yes, most MGs have top mounted feed systems and bottom mounted gas, but muzzle climb isn't as important on a crew served weapon that's intended for bipod and tripod use.

Everything is a compromise. We have the weapon designs we have because they tend to be the least bad set of compromises.

One disadvantage of the top mounted mag is that it can be a target indicator. A book I read about fighting in the Pacific theater talked about how good the Japanese were at camouflage, including tying brush and leaves to the top mounted magazine of their light MGs. So you just shoot below the shaking bush to hit the gunner.

BSW

*Recoil operation brings its own advantages and disadvantages, chief among which is that no successful recoil operated personal weapon has ever been mass issued that I'm aware of.
 
I would think, the old rule applies. Form follows function. If you want something you can pull in tight to your body, you need something narrow. A big magazine hanging off the side gets in the way. On the top, optics have troubles, and it can allow gunk from the field to get into the action easily. Also, a mag loaded generally keeps the weapon upright when hanging on the bottom.
 
Calico's helical top load magazine was an interesting approach, which even worked in full auto.

Another "left field" is the FN P90 top feeder, with the rounds held transversely across the arm and spun into alignment at the action.
That keeps the overall height of the magazine low, which obviates need for offset sights and the like. It does have the problem of not scaling up for longer-length cartridges.

The design that does not seem to have had much use would be a double-lateral magazine, which would balance the loading to either side of the arm. Something along the lines of the double drum used by the MG 42 perhaps. (Not the 50 single drum, that was merely a case to hold a belt of linked ammo.)

The Johnson LMG, with its 20 round box magazine of .30-06 on a BAR-sized arm was criticized for how that loaded magazine wanted to cause a port list into the arm.
 
A loved one has a 45 ACP that loads from the side, with a 30 round magazine. It looks like an SMG but it's semi-auto. The balance is really goofy, so I guess that's one disadvantage. The only other I can think of is fighting in close quarters can be obstructed in terms of positions behind and moving to/from cover.
 
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Many years ago in Egypt, I had a Bren gun that we found at a British dump near Siwa oasis. The Bren feeds from the top, and as a result the sights have to be on the left side of the gun -- so a left-hander can't use it very easily,

The Johnson Light Machinegun was magazine-fed from the left, and was quite clumsy and awkward to carry as a result.
 
The 1989 Krag-Jorgenson US service rifle was loaded from the side and fed in a manner that wasn't quite bottom-up.


One thing to really ponder is the pendulum effect of a larger magazine being located below the rifle's action.

For a weapon that only weighs somewhere between about 6 and 10 lbs, generally speaking, having ammo and a feeding device hanging off as a lever arm to one side, or out the top is going to add rotational torque while you're trying to hold it steady straight up.


Consider the keel weight of a sail boat.

[resize=500] 2000px-Capsizing_effect_of_keel.svg.png [/resize]

You want that weight down below, keeping the rifle stable, not sticking off to one side trying to tip the gun over.
 
Calico's helical top load magazine was an interesting approach, which even worked in full auto.[/I]

Another "left field" is the FN P90 top feeder, with the rounds held transversely across the arm and spun into alignment at the action.
That keeps the overall height of the magazine low, which obviates need for offset sights and the like. It does have the problem of not scaling up for longer-length cartridges.

The design that does not seem to have had much use would be a double-lateral magazine, which would balance the loading to either side of the arm. Something along the lines of the double drum used by the MG 42 perhaps. (Not the 50 single drum, that was merely a case to hold a belt of linked ammo.)

The Johnson LMG, with its 20 round box magazine of .30-06 on a BAR-sized arm was criticized for how that loaded magazine wanted to cause a port list into the arm.



As well as the bottom mounted helical magazine of the Bizon SMG.
 
As someone who has carried an M16 over many a mile, I would think having a magazine hanging out the side of the rifle would be very awkward and much more difficult to deploy quickly when necessary.
 
Dont forget the shifting weight of the magazine as it empties. This is a 'real time' center of gravity shift, taking place while in use, with side mounted magazines and with a top or bottom fed. The side mounted magazines have more of an issue with such, when it comes to controling aimed fire and full auto.

The side mounted mags make the weight shift horizontal as well as vertical, unlike top/ bottom mounted mags, which can be longer and carry more ammo without major control while firing issues, due to the shift of weight while doing so, but a large cap top mounted mag might become a balance while carrying it around. Low center of gravity for a large cap mag, a compromise would be the length.


Also, In the dark, 'hands find hands" makes for easier instinctive reloading.
 
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The Johnson LMG had a 25-round, single-stack magazine, with the feed lips machined into the receiver. That made the magazine much longer than a comparable double-stack magazine, and made the gun quite difficult to carry.
 
Top mag requires offset sights, or very tall sights --not a good solution unless the stock comb is necessarily high (see: P90 & AR57)

Mag out the side generally makes the gun impractical for slung carry (see: old photos of Nazis hopelessly trying to patrol comfortably with their MP28s)

I will say that both side and top-loading mag systems seem best suited to short, 'squat' designs, since they allow for a short overall length without near the drawbacks of a under-side magazine in a bullpup arrangement. I am actually looking into the possibility of a side-feeding bullpup design that uses P90-like magazines which may be inserted onto either side of the receiver.

TCB
 
On the other hand, a "conventional" bottom 30 round magazine can keep you from getting into as low a prone position as you might like. NRA lets you use a 20 round AR magazine or one of lower capacity or a single shot adapter only if of the same external dimensions as the 20. Tradeoffs all the time.
 
Good comments and discussion.

No one has mentioned the tube magazine commonly used in lever action centerfire and 22 rifles.

The Spencer used in the Civil War had the magazine in the butt stock and was loaded from the rear. It was quick to reload using the Blakeslee Cartridge Box. The original Spencer main disadvantage was the ammunition of the period.

For use in modern times the buttstock makes for limited ammunition capacity and size of the cartridge.

Then there is the Henry that loads from the front of the magazine tube. It proved itself to a practical design during the Civil War and has evolved since then.

The traditional lever action rifle has withstood the test of time well and remains a very practical long gun. It is narrow, has a flat receiver, smooth forearm and barrel that are snag free, easy to carry with no worries about losing the magazines. It is easy to reload and can be topped off with a single round unlike the Garand. It's magazine capacity is limited with current military doctrine.

Going prone no problem. Excellent in heavy brush and woods. Lightweight for long hikes.

With the designs such as the 1894 Winchester it can handle powerful cartridges. The design of the lever gun is so close to perfect that few changes have been made to it. Stainless steel, laminated stock, sights mounted of the receiver such as Williams and Skinner are merely refinements making the gun even more durable for rough usage. With the modern top rail a scope can be quickly detachable,
 
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