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pjp
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PostPosted: Fri Nov 09, 2012 3:28 am    Post subject: Reply with quote

BoneKracker wrote:
If you have javascript disabled, it erroneously says the picture has been deleted or moved. If you toggle it on, it erroneously then loads the first picture in the series, which is a sleeping puppy, not the target.
Interesting. It was there after sikpuppy indicated it was there. Maybe I'd enabled javascript, but it didn't "work" until I went back or something like that.
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wswartzendruber
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PostPosted: Fri Nov 09, 2012 9:15 pm    Post subject: Reply with quote

The story to far: Picture
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Bones McCracker
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PostPosted: Sat Nov 10, 2012 12:58 am    Post subject: Reply with quote

Where's the bolt, charging handle, and lower receiver group? Is that all there is to the stock, or is there a piece missing?
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wswartzendruber
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PostPosted: Sat Nov 10, 2012 4:53 am    Post subject: Reply with quote

That's all there is to the stock on a carbine. The bolt carrier group is in the mail, possibly lost. It's overdue. The lower receiver group is being held for ten days per California law. All the parts that go in the lower receiver are in the bag. I have some armory work ahead of me. I even had to buy special tools.
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pjp
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PostPosted: Sat Nov 10, 2012 5:15 am    Post subject: Reply with quote

wswartzendruber wrote:
The lower receiver group is being held for ten days per California law.
Any idea why? Background check, or just bureaucracy?
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sikpuppy
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PostPosted: Sat Nov 10, 2012 5:28 am    Post subject: Reply with quote

pjp wrote:
wswartzendruber wrote:
The lower receiver group is being held for ten days per California law.
Any idea why? Background check, or just bureaucracy?

They are like a father with their kids train set on Christmas Day, they just have to "test it" to "make sure it works".
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Bones McCracker
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PostPosted: Sat Nov 10, 2012 5:36 am    Post subject: Reply with quote

pjp wrote:
wswartzendruber wrote:
The lower receiver group is being held for ten days per California law.
Any idea why? Background check, or just bureaucracy?

Probably a mandatory "cooling off period", as bureaucratically applied to a mail order purchase. They don't want people to be able to run out and buy a gun suddenly because they're angry, so they make them wait. What they don't realize is this creates a good reason to own one; you also can't run out and buy one if you suddenly have a need for personal protection.
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wswartzendruber
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PostPosted: Sat Nov 10, 2012 7:11 am    Post subject: Reply with quote

It's a background check (I think) and a cooling-off period.
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notageek
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PostPosted: Sat Nov 10, 2012 7:18 am    Post subject: Reply with quote

Should you be worried?
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wswartzendruber
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PostPosted: Sat Nov 10, 2012 7:42 am    Post subject: Reply with quote

Nope.
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pjp
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PostPosted: Sun Nov 11, 2012 5:04 am    Post subject: Reply with quote

lol @ cooling off period. Because someone who wants to react while "hot" is going to order a lower receiver to do the job. A .38 Special can be had cheap and w/o a check, so if someone really wants to do the job... hooray for lolgov.
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wswartzendruber
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PostPosted: Wed Nov 14, 2012 7:24 am    Post subject: Reply with quote

So yeah, it really does look like the bolt carrier group got lost in the mail.
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Bones McCracker
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PostPosted: Wed Nov 14, 2012 5:48 pm    Post subject: Reply with quote

wswartzendruber wrote:
So yeah, it really does look like the bolt carrier group got lost in the mail.

Look out. Some USPS worker is slowly assembling an AR-15. :lol:
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wswartzendruber
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PostPosted: Thu Nov 15, 2012 7:07 am    Post subject: Reply with quote

Actually, all I need to do is keep the ejection port cover open and finger a round in the chamber. All I'll have to do then it smash it with a metal pin.
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wswartzendruber
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PostPosted: Tue Nov 20, 2012 1:57 am    Post subject: Reply with quote

I built the lower receiver today, and pieced the main portions together. It suffered one ding.
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Bones McCracker
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PostPosted: Tue Nov 20, 2012 2:10 am    Post subject: Reply with quote

So what will be done about the lost bolt carrier group, etc.?
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wswartzendruber
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PostPosted: Tue Nov 20, 2012 2:23 am    Post subject: Reply with quote

I'll be depressed about it until I decide to put out the money for a new one, or until it magically shows up in the mail.
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dmitchell
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PostPosted: Tue Nov 20, 2012 2:25 am    Post subject: Reply with quote

What's a bolt carrier group?
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wswartzendruber
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PostPosted: Tue Nov 20, 2012 2:26 am    Post subject: Reply with quote

The bolt carrier group holds the round in place while it goes off. The round travels down the barrel, causing a pressure build-up. This new pressure ends up traveling down a gas tube that causes the bolt to unlock, move back, eject the old casing, and chamber a new round. It's the main moving part of the weapon.
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dmitchell
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PostPosted: Tue Nov 20, 2012 2:31 am    Post subject: Reply with quote

Clever design. Thanks!
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Bones McCracker
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PostPosted: Tue Nov 20, 2012 3:44 am    Post subject: Reply with quote

Nice drawings of bolt (1) and bolt carrier group (2-4), easy to understand:
http://www.behance.net/gallery/BOLT-CARRIER-GROUP-PROJECT/4197729

Exploded diagram of bolt carrier group:
http://www.ar15.com/content/guides/parts/boltCarrier.gif

Nice photograph of apparently poor quality bolt carrier group disassembled to operator maintenance level:
http://sgcusa.com/images/supporting_images_large/LMT_Enhanced_Full-Auto_Bolt_Carrier_Group_L7Q3_B.jpg

Exploded Diagram of AR-15 (complete disassembly):
http://ompldr.org/vZ2RrNw

The AR-15 design sucks (or maybe it was the specification) in my opinion. It's an unacceptable trade-off of reliability for reduced weight. The weapon overall is an excellent design, but the direct-impingement gas-operation mechanism, specifically the interface between the gas tube and gas key are entirely unacceptable, in my opinion.

A normal gas-operated weapon uses the exploding gases from within the barrel, just before the bullet exits it while they're still under high pressure, vented through a tiny hole in the barrel, to drive back a rod-like piston, which pushes the bolt assembly (in this case called the "bolt carrier group) back against a spring, which temporarily collects and stores that kinetic energy as potential energy, and then releases it again as kinetic energy, driving the bolt back forward, etc.

The AR-15 is a special type of gas-operated weapon that uses "direct impingement" (which I say sucks). Instead of pushing back a rod, the gases themselves travel through the gas tube all the way back to the receiver, where they are imparted to the bolt carrier group, blowing into the "gas key" (which is that smaller tubular thing you see screwed onto the top of the bolt carrier), pushing back the bolt itself. This design innovation eliminates entirely the need for any gas piston and housing, reducing the weight substantially. As one might imagine, heavy-ass weapons are a major complaint of infantrymen, so this is a heavily-weighted requirement.

The problem with the direct-impingement design is that those hot gases from the exploding round end up venting right into the upper receiver, which soaks up or burns off lubricating oil and coats all the parts with nasty carbon and corrosive by-products of the propellant which are very hard to clean off and can accumulate dangerously. This is why AR-15 variant weapons jam in heavy firefights, right when you absolutely don't want them to be jamming.

The design should be re-worked to either:

a) somehow vent the gases outside the receiver (and hopefully away from the operator's face, given that they undoubtedly are not the healthiest stuff to be breathing); or

b) utilize a short-stroke gas piston which eliminates most of the weight but still maintains separation of the propellant gases from the receiver.
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wswartzendruber
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PostPosted: Tue Nov 20, 2012 4:43 am    Post subject: Reply with quote

There are aftermarket piston mods for the AR-15 platform. There isn't consensus on if it's worth it, though.

To the weapon's credit, there is the forward assist that Colt decided was a definite necessity. For whatever reason, Armalite didn't include it.
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Bones McCracker
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PostPosted: Tue Nov 20, 2012 5:39 am    Post subject: Reply with quote

Yeah, just what you need in a firefight. A forward assist. I'd rather have a weapon that didn't have a tendency to jam if you put a few hundred rounds through it in a short time. It's still a great weapon, but I think it needs an integral, thoroughly-tested short-stroke gas piston. I didn't know there were such modifications available, but I wouldn't trust my life to an un-proven mod so central to the weapon's basic operation.
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wswartzendruber
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PostPosted: Tue Nov 20, 2012 5:50 am    Post subject: Reply with quote

How do those things respond to sand? From my perspective, it's another moving part that needs regular cleaning maintenance.
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Bones McCracker
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PostPosted: Tue Nov 20, 2012 6:46 am    Post subject: Reply with quote

wswartzendruber wrote:
How do those things respond to sand? From my perspective, it's another moving part that needs regular cleaning maintenance.

Ever heard anybody bitching about it? They (gas pistons, not necessary "short stroke" ones) are on the M249 and M60, as well as many other light machine guns and assault rifles. It's pretty much a self-enclosed system, like a shock absorber.

That gives me an idea. Maybe the piston could largely be replaced by a cylinder of non-compressible gas! I wish I wasn't too lazy to check to see if that's been patented.
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