Why the movement towards "enclosed" bolts?

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Eightball

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I got to thinking the other day--why is it that nearabouts every new rifle design today has a daggone near completely enclosed bolt mechanism? Take the AR--completely enclosed. The AK is less so (still has a handle on the thing), but has a "dust cover." Same with the G3, FAL, G36, SCAR, ACR, AR10, Barrets, SU16s, and nearabouts any other newer rifle. Compare that to, say, a Garand, with a bolt that is, more or less, completely "exposed." The M1 Garand, M1 Carbine, M14(+derivatives), possibly the SKS (kinda middling), SVT, G43 (yeah I know, some of those are stretching it a bit), etc. Bolt actions have it for obvious reasons, but even things like the Krag-Jorgenson, which you didn't necessarily feed from the top, had an open bolt still. I know, I know, I'm making some "you DIDN'T just ask that" kind of observations, but just to illustrate what I'm trying to get at.

My question is, primarily, why? Did I just overlook something in my tired, college-student brain? I mean, it isn't like those more "exposed-bolt" type firearms had all that many problems floating around due to the fact that the bolt was out in the open.
 
Eightball, you ever hear the old adage "live and learn"? Well the more crap you keep off the bolt area, the less likely you will have a problem with function. Most all the rifles you mentioned are rifles made to use in highly arid desert areas.
 
Well, let me summarize all the posts that the old farts on here are going to say eventually.

"Why? I'll tell you why, son! Because shooters these days are too damned lazy to keep their guns clean! They've got their little plastic Mattell guns that they think don't need cleaning, and they don't clean them! Then the bitch and complain when the darned thing jams! 'Oooooooh... my AR-15 jammed... why do I have to clean it so much?' WELL I'LL TELL YOU WHY!!! BECAUSE BACK WHEN I WAS A SOLDIER AT THE BATTLE OF BUNKER HILL, WE HAD TO KILL DINOSAURS WITH REMINGTON THUNDERBOLT .22 AMMO OUT OF PEASHOOTERS!!! THAT CRAP WAS DIRTY, AND WE HAD TO CLEAN THE BOLTS BY REMOVING THEM AND CHEWING THE FOULING OFF WITH OUR TEETH!!! WE DIDN'T HAVE THAT FANCY TEFLON CRAP, EITHER. AND YOU KNOW WHAT? WE LIKED CHEWING LEAD OFF OF OUR OPEN BOLT RIFLES. HELL, WE LOVED IT!!!!!!!!!!!!!!! 'WOOPEEEE LOOK AT ME!!!! I HAVE LEAD POISONING AND MY TEETH ARE EITHER BLACK OR NOT-EXISTANT!!!!!!!! AT LEAST I'M NOT ONE OF THOSE COMMIES LUGGING AROUND A CLOSED BOLT RIFLE!!!!!!!!!!!"

But that's just a guess of what they're going to say. Not sure what they're gonna say for real ;)
 
Kcmarine, you forgot about walking uphill both ways while doing it. Other than that, I'd say you summed it up just fine.
 
Would a more enclosed designed be more susceptible cold weather problems, like icing?

I only ask because I heard that the M14 did better than the AR in that regard.

Or is the issue more complicated than that?
 
CypherNinja, how many current conflict zones do you see in sub or close to freezing areas? I agree that the M-14 would be better suited for freezing battle areas. But most battle rifles today are manufactured to be utilized in more tropical and arid regions of the world. Someone chime in if you have evidence to the contrary.
 
kcmarine said:
Well, let me summarize all the posts that the old farts on here are going to say eventually.
Click to expand...

The thing most older people are going to say (for real) about your post... what the &^%$# does a 17 year old snot nosed wannabe know about anything?

But then... that would not be "High Road" would it... to stigmatize someone because of age difference....
 
The thing most older people are going to say (for real) about your post... what the &^%$# does a 17 year old snot nosed wannabe know about anything?

But then... that would not be "High Road" would it... to stigmatize someone because of age difference....
Click to expand...

Calm down, I think your the only one that didn't find it funny.
 
back to the OP...

in the case of the AR, it's gas that directly blows the bolt back. if the bolt wasn't enclosed, there wouldn't be a seal, and the result would be a stiff breeze in your face accomplishing nothing.
 
The M16 / AR system has basically an aluminum tube with a steel bolt in it sliding along on some rails. Aluminium is light weight but not as strong and durable as steel. I'm pretty sure the "enclosed" reciever was a must for strenth and gas system performance but also aids in accuracy and enables them to keep the rifle light weight. The AK on the other hand has a dust cover. Needed for more than one reason. Keeps dirt out and body parts away from moving components. It's not required for proper operation though and doesn't add any strength to the reciever.
 
I'm in that age group where I have shot both, appreciate both, over 50, and I thought it was gut bust'n funny.

I never did get all the lead out between that last molar....BUT I LIKE IT THAT WAY.
 
I really don't see the difference in the two for 'keeping dust out'; it's most likely related to having a stronger structure. Think about it; dust or sand is going to get in your weapon just as much with an 'enclosed' bolt as it is with a more 'exposed' one. It's not as if the bolts on both of the different rifles in question do not open to eject a spent casing, and both designs are NOT going to prevent finely-grained particles from getting in if they are dumped into the receiver and need to open to eject and load another round into battery. I'd say it's more of a design perk than KEEP DUST OUT YEEARGH.
 
The trend is not a new one.:)

In 1889, Marlin introduced its first solid-top, side-eject lever gun with a precision-fit bolt to keep the rain and dirt out, to compete with the open-top Winchesters.

marlin_model1889.jpg
 
are you talking enclosed bolt as in the bolt lugs locking inside the bbl. or enclosed bolt as in a dust cover of some sort? the Japs had dust covers on the Arisaka action bolt rifle most of these were discarded by their troops. check out some of the high end ($) bolt action Blaser rifle they have both.
 
Compare that to, say, a Garand, with a bolt that is, more or less, completely "exposed." The M1 Garand, M1 Carbine, M14(+derivatives),
Click to expand...

There are advantages to the "open bolt" system of the Garand. You can read about the decision of Winchester to use a open bolt for the Carbine in the book "War Baby". They found that cartridge ejection was more certain when there was no receiver walls to get in the way. With an open bolt system the operator can instantly see a cartridge jam or an empty weapon. An open bolt system is also easier to clean.

More modern designs emphasize reduced manufacturing. The Garand, M14, and M1 Carbine used two lugged bolt designs. Their receivers were expensive forging, required a lot of expensive and complicated machining. All had side mounted operating rods.

But I think the real starting point is with the locking mechanism. That drives the configuration of the rest of the design.

If you notice, most semi autos use a multi lugged bolt similar to the M16 bolt. This type of bolt and associated carrier are very common. The upper or the receiver is essentially a tube. The less holes you cut in the tube, the stronger it stays. The closer you can get to a tube, the cheaper the receiver. Tubes are easy to make.

A cover is necessary for the AK and the FN because of the chance of getting your hand between the back of the bolt and the receiver.

There are other influences on designs, that are not apparent at first. The Garand and the M14 were designed to be fed from the top with clips. In the book "US. Rifle M14" by Blake Stevens, there is a long post WWII memo from the user about the evils of magazines. After WWII this idiocy was understood for what it was, but prior to WWII, this faction was so dominant that Garand was forced to get rid of his box magazine and make his design loadable from the top with a eight round clip. After WWII, the Neanderthals still had so much influence that in the 50’s, you see 20 round stripper clips for the FN/FAL, and the M14 magazine was called a “semi detachable” magazine. To placate this faction, the M14 has a clip slot on the top. I doubt anyone ever used it to reload their magazine in battle.

As stated before, having an enclosed system is not evil. There are a lot of enclosed systems that are very successful.
 
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This, of course, is just my 2 pfennings, but I call BS on the "closed bolts keep the weapon cleaner". My M4, after firing 10 rounds, is *way* dirtier than my Mosin after the same amount. All that gas that pushes the bolt back is filled with carbon and other filth. It makes for a weapon that *has* to be kept 110% cleaner than a old-school bolt action, or dare I say, even a Garand, to function reliably in combat situations.
 
Closed/covered receivers are nothing new. Arisakas and Siamese mausers had dust covers. There were even canvas action covers for the supposedly 'mud-proof' enfield rifles.
 
This, of course, is just my 2 pfennings, but I call BS on the "closed bolts keep the weapon cleaner". My M4, after firing 10 rounds, is *way* dirtier than my Mosin after the same amount. All that gas that pushes the bolt back is filled with carbon and other filth. It makes for a weapon that *has* to be kept 110% cleaner than a old-school bolt action, or dare I say, even a Garand, to function reliably in combat situations.
Click to expand...
You're confusing debris/mud/dirt/gunk from the environment with carbon and powder residue from the cartridge/gas system. The FAL and AK have an enclosed bolts, and they're no dirtier than a M1 or M14 inside (or at least not appreciably so). The AR is dirtier not because its bolt is enclosed, but because it uses direct gas.

Enclosed bolts have two advantages:

1. External debris is kept out of the action to a much greater extent

2. Enables the mounting of optics directly over the bolt (in some designs)

Mike
 
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