A couple of weeks or so ago, a question was asked about the merits of side-feeding rifle magazines. This concept was promptly rejected and it is certainly true that such mags have seen very little use, but I thought the idea deserved a run around the block, just to rehearse the arguments.

First of all, only two weapon families with side-mags have seen combat, AFAIK: the Johnson family of rifles/LMGs developed from the late 1930s to around 1944 (which also tried various other feeding systems), and the legendary German FG 42 of mid/late WW2. Interestingly, both of these were developed with the same purpose in mind: to provide special forces in general and paratroops in particular with the firepower of an LMG with little more size and weight than a rifle.

For more info about both weapons including range tests, try the excellent Forgotten Weapons site: https://www.forgottenweapons.com/

The side-mag besides, these weapons shared other characteristics: most notably, they both fired full-auto from an open bolt, semi-auto from a closed bolt, to combine single-shot accuracy with better cooling in auto. 

The FG 42 layout was effectively a "semi-bullpup" design, with an overall length reduced accordingly.

With the later Johnson LGMs, the magazine could be closed off from the feed, so that it was possible to maintain a steady rate of semi-auto fire by inserting clips or individual rounds while keeping the magazine full, ready for auto use. 

The major problem with both weapons is that they were designed around the full-power rifle/MG ammunition, which made such light guns something of a handful. Now, if Johnson had stuck with the .276 Pedersen, which developed only about half of the recoil, that could have made  a very neat package. 

The main practical advantage of the side-mag is that it permitted a very low firing position for better concealment. The main disadvantage is that the weight distribution with a full mag can be somewhat unbalanced. However, both weapon families seem to have achieved a degree of popularity among their users, if not the manufacturers (the FG 42 was initially VERY expensive, partly due the use of exotic alloys to keep the weight down.

Of course, the weight imbalance issue would be less of a problem now, with polymer magazines (not to mention polymer-cased ammo).

OK, open fire! 

autogun said:

OK, open fire!

Alright.

Did their layout have any advantage over asimilar design in top feed that isn't compensated for by the top feed's better balance and ability to be easily reloaded from either side? 

BlasTech E-11 Blaster Rifle in Galaxy far away, 

Side charging ar15 mag feeding Voere bolt action dressed up by Hera arms

autogun said:

The main practical advantage of the side-mag is that it permitted a very low firing position for better concealment.

Is the ability to get into a very low firing position the "main" advantage of a side mag, or is it actually the only advantage?

autogun said:

The main disadvantage is that the weight distribution with a full mag can be somewhat unbalanced.

There are other drawbacks of the side mag which are at least as bad, if not more so.

Magazine location is easy to use by right-handed shooters, but awkward for lefties.

Carrying a rifle with side mag can be problematic for a right-handed soldier versus a rifle with conventional vertical mag.

autogun said:

First of all, only two weapon families with side-mags have seen combat

Tony, are you intentionally leaving out a whole bunch of submachine guns that stemmed from the MP-18 and MP-28 (Erma EMP, Lanchester, Sten, Sterling etc)?

albumwar2.com

Jeff (Jefffar) said:

Did their layout have any advantage over asimilar design in top feed that isn't compensated for by the top feed's better balance and ability to be easily reloaded from either side? 

I think so. Taking the best-known example of a top feeder, the Bren, the in-line top feed meant that the sights were pushed to one side. As a result, the Bren could only be aimed with the right eye - lefties need not apply! 

Also, I think that the either-side top feed reloading was only an advantage if used as a two-man weapon. A side-loader is probably faster to change mags - it's only a one-man weapon. 

mpopenker said:

Tony, are you intentionally leaving out a whole bunch of submachine guns that stemmed from the MP-18 and MP-28 (Erma EMP, Lanchester, Sten, Sterling etc

Yes - I was keeping to one class of weapon, SMGs are sufficiently different to be looked at separately, IMO

stancrist said:

Carrying a rifle with side mag can be problematic for a right-handed soldier versus a rifle with conventional vertical mag

Yes it can, depending on the design and the circumstances it is used in. A bottom-mounted mag (i.e. virtually all current ARs) can be awkward to change especially when lying flat.

Incidentally, I am quite intrigued by the Johnson which combined a horizontal feed with the ability to add strips or rounds, leaving the mag full (not easy with top-feeds, I suspect, and considerably worse with bottom feeds). I can imagine this feature being very handy in some tactical circumstances.

Which leads to a question: is there any doctrine in any army concerning when to change partially used mags? If facing a succession of heavy attacks, soldiers are likely to want to keep a full mag on the gun, resulting in piles of part-filled mags around them (?) 

autogun said:

I think that the either-side top feed reloading was only an advantage if used as a two-man weapon. A side-loader is probably faster to change mags...

Looks to me like mag changes are at least as fast (if not faster) with a top-loader than a side-loader.

BREN (right hand shooter/right hand mag change)

BREN (right hand shooter/left hand mag change)

FG42 (right hand shooter/left hand mag change)

FG42 (left hand shooter/left hand mag change)

Johnson LMG (left hand shooter/left hand mag change)

Stoner 63 (right hand shooter/left hand mag change)

autogun said:

Incidentally, I am quite intrigued by the Johnson which combined a horizontal feed with the ability to add strips or rounds, leaving the mag full (not easy with top-feeds, I suspect, and considerably worse with bottom feeds). I can imagine this feature being very handy in some tactical circumstances.

I cannot imagine that this feature would today be considered as worth the complexity and weight.

When the Johnson LMG was developed, the USMC standard issue rifle was the M1903 Springfield.

There was some logic to designing the LMG so it could be loaded using M1903 5-rd stripper clips.

Especially since the Johnson M1941 rifle also was designed to be loaded using the same 5-rd clips.

autogun said:

Which leads to a question: is there any doctrine in any army concerning when to change partially used mags?

I cannot say.  I do not know what current doctrine is on that matter.

autogun said:

If facing a succession of heavy attacks, soldiers are likely to want to keep a full mag on the gun, resulting in piles of part-filled mags around them (?)

Typical practice in previous wars has been to refill empty (and part-filled) mags during lulls in the fighting.