AR stuff...

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I'm wondering the same thing about the bushy dissipator... never held one of those either. Is it a real full length gas system, or does it have the ported gas block/tube under the handguards at the M4 position?
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I have an RRA midlength. It has a normal gas block at the front sight. Supposedly, this is superior to the M4 gas block position for a 16" barreled carbine. Something about the pressure curve. I don't know the details.

The Dissipator has a gas block under the handguards, but I wouldn't consider that a detriment. It was done to extend the sight radius to the same as a 20" barrel while keeping the handy carbine barrel length. There has to be a certain amount of barrel after the gas block to keep the rifle funtioning reliably so they moved the gas block back. I agree they look funny, but the design has some benefits.

abbl-16dm4a.jpg
 
interesting...

So, why are there still so many brand new 'pre-ban' uppers around?
Does the ban forbid the sale of UPPERS and LOWERS with the 'evil' features, or is it just complete guns?

Also, I have only found 'upper halves', which are the barrel, the grip, and the sights. What's the other 'half' of the upper?
 
So, why are there still so many brand new 'pre-ban' uppers around?
Does the ban forbid the sale of UPPERS and LOWERS with the 'evil' features', or is it just complete guns?

Also, I have only found 'upper halves', which are the barrel, the grip, and the sights. What's the other 'half' of the upper?
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Didn't we just have this question a couple days ago?

Yes: Why so many pre ban uppers for AR15s?

"This upper is pre-ban" is short-hand for, "It's only legal to put this upper on an AR15 lower with pre-ban status, or a LEO lower."

-z
 
You can still buy brand new preban everything, except for the lower reciever.

You can call up Bushmaster and order a brand new preban upper and collapsible stock right now.

Its just not legal to put them on your lower unless your lower was part of a complete rifle in September, 1994.
 
Yeah, I kind of never payed attention to AR threads...I never thought I would buy an AR!

anyway, whats the other half of the upper? What's missing?
 
Wait a sec...I thought you loaded the rifle with your shooting hand??

Wouldn't it be easier to load like that than to hold the rifle up by the pistol grip? It would seem that way...
 
Wouldn't it be easier to load like that than to hold the rifle up by the pistol grip?
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Back in the days of big heavy long traditionally stocked rifles top-loaded with a clip, that was the thinking of the day. (Mausers, Springfield '03s, M1s, etc).

The AR is light enough that holding it by the pistol grip ain't a chore, and the support-hand reload is wicked fast. Kinda like swapping a pistol mag actually... hit the mag eject button, dry mag drops free, slap in a new one and hit the bolt release (think slide stop).

Watching the guys who really know what they're doing on the field with those things is just amazing. As in... "he really did reload just now, right? I didn't hear a break in the fire string..."

:)


-K
 
Wow, cool!
I figured the only gun you could reload while keeping firing grip was a bull-pup design...guess not.

Still wondering about those 'half-uppers' though...
 
No, you retain the firing grip while ejecting and replacing a new magazine.
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The FAL is operated that way also. The charging handle for the FAL is on the left side of the receiver. It sounds strange, but it's very natural once you try. It also allows you to get back to shooting very quickly.

anyway, whats the other half of the upper? What's missing?
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Here's a pair of complete uppers, Rock River's in this case. (On the pre-ban, note the flash suppressor and right under the sight in front of the sling mount is the bayonette lug) You can also see the two tabs under the upper receiver where the pins go through to hold it to the lower receiver. One is at the front and one is at the rear. This whole assembly can legally be mailed to you without the need for a transfer through a dealer.

Compare this with the pic of the Dissipator barrel pic that I posted above.
ustda2cm.gif
 
well.. I'd not call it "halves" of an upper, but the difference between a complete and an incomplete upper is --


complete upper -- includes bolt and carrier assembly and charging handle
incomplete upper -- doesn't include bolt/carrier, etc.

bolt and carrier and such run around $125 or so these days I think. So that's the price difference give or take you should see.

Also, there is a diff between M16 carriers and AR-15 carriers -- the AR carrier is cut away underneath so that it won't trip an autosear.

-K
 
Those were EXACTLY the uppers I was looking at!
So those are complete, even though they say 'halves'?
I guess they mean half of the WHOLE RIFLE, instead of just half of the upper. I guess I just thought too hard there...


Oh...this just came to mind!
How much do the handguards weigh? I am wondering because it would seem that the longer the handguard, the larger the sight radius (since the forward sight is at the end of the handguard). Anyway, why would one opt for a smaller handguard and sight radius? Is weight a major factor?
 
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I guess they mean half of the WHOLE RIFLE
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You've got it.

How much do the handguards weigh? I am wondering because it would seem that the longer the handguard, the larger the sight radius (since the forward sight is at the end of the handguard). Anyway, why would one opt for a smaller handguard and sight radius? Is weight a major factor?
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The handguards themselves are plastic and don't weigh much at all (except for free floating setups, but that's a whole 'nuther conversation). The added weight of the longer barrel is due to the barrel itself. This is especially true with heavy barrels due to their thicker profile. The harder to find government A1, A2 and M4 profiles are thinner under the handguards so they are lighter (they have less metal). The heavy barrels are stiffer though so should be more accurate (actually more consistant) and will absorb and dissapate more heat. ie. they run cooler. Interestingly, a 20" barreled rifle with a thin A1 or A2 government profile barrel will be lighter than a heavy barreled carbine. You can go very light with a thin profile carbine barrel and some very lightweight receiver components (see the Bushmaster Ladies Rifle thread)


Folks choose rifles or carbines for various reasons. People like carbines because they are shorter and easier to manuever in tight places. If you plan to put a red dot or scope on a carbine then the short sight radius won't matter so much. M4 styled carbines are popular now because they look cool. Some of the more savvy folks may choose one of the lighter barrel profiles for a lighter gun. Other folks may choose the longer barrels for the longer sight radius, they may want more velocity. Some may just like the look of the 20" barrels better.
ARs are available in so many flavors, there are all kinds of reasons to build/buy them one way or another. Figure out what you want to do with the rifle and then find/buy/build something that will fit your need. If your needs change, no big deal, buy another upper and you can swap them back and forth depending on your mood.
 
The heaviest two parts of the "complete" upper are the usually bolt carrier assembly and the barrel, which are both steel.

Most handguards are made of fiberglass, plastic, or aluminum. An extra 2-4" of that weighs a few ounces.

The barrel profile (how thick it is throughout its length) is a big contributor to weight. A thing A2-type barrel will not very much. An Hbar ("heavy barrel") or bull barrel will weigh much more.

The difference in weight going from 16" to 20", for same barrel profile, will be mainly that 2 or 4" long rod of additional steel.

-z
 
See...this is how I figure:

First, I saw a 20" with the handguard that was only medium length. Then I saw a 20" with the handguard almost at the tip of the barrel. What I thought was "Why sacrifice all that extra sight radius? If the barrels the same length, might as well have the handguard to the end."

Just my take on it, but I can't see any advantages to a shorter sight radius...then again, I am not experienced in guns...

edited to add: I found out what that thing was...forward assist. Of course it was located on the left side instead of the right...
 
There are three gas system lengths that I'm aware of:

1. Full or rifle length. Gas block / front sight tower is approx 13" from receiver.
2. Mid-length. Gas block / FST is approx 9.25" from receiver.
3. Carbne-length. Gas block / FST is approx 7.25" from receiver.

Then throw into the mix the different barrel profiles: A2, straight Hbar, "M4", bull, etc.
Next you can you mix and match handguard length. If the handguard covers the gas block, the gas block will have to be low-profile. If the gas block is further out than the handguards, the gas tube will be exposed (rare).

If you are not using iron sights, a longer handguard can offer more control since you can grasp it further towards the muzzle. It will also provide a "heat shield" which can be useful if you shoot it a lot and then drop it on a tac-sling. Finally, you can hang more "junk" (flashlights, lasers, whatever) off a longer handguard -- not my cup of tea, anyway.

The lower receiver is the "firearm" part.

For lots of AR15 information, go to http://www.AR15.com

-z
 
First, I saw a 20" with the handguard that was only medium length. Then I saw a 20" with the handguard almost at the tip of the barrel. What I thought was "Why sacrifice all that extra sight radius? If the barrels the same length, might as well have the handguard to the end."
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Are you sure those were 20" barrels you were looking at? It sounds like you were looking at a 16" midlength handguard carbine and a 16" Dissapator carbine.

Your argument has a lot of merit. It sounds to me like you would prefer either a 20" barreled rifle or a 16" dissapator carbine. Which one depends on whether you'd prefer the handiness of the 16" barrel or the extra velocity of the 20" barrel. You can get either one down to a very managable weight if you choose components carefully.

I'm a huge fan of carbines and have shorter barreled rifles of all flavors. However, my 16" RRA carbine shows off a HUGE fireball everytime I fire it. That's a lot of burning energy getting vented uselessly into the atmosphere. I love the carbine and wouldn't give it up for the world, but my next one is going to be a lightweight 20" A2 Govt. barreled flat top.
 
Yes, it was a 'dissipator', if I recall right. I can't remember where I saw it though...

Is anyone still selling new pre-ban lowers? I would like to avoid the huge fireball I've heard so much about.
I ddin't think much of the so-called 'fireballs' until I saw a photo of a Desert Eagle being shot, with a huge circular fireball a few feet in front of it. It was a sweet photo...but not one I would like to experience...
 
Is anyone still selling new pre-ban lowers?
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Unfortunately, you can't legally build a pre-ban. You can only buy a rifle that was already built with a flash suppressor, collapsable stock, etc. and documented before the AWB in 94. Perhaps after next Sept. you can build one.
 
During the daytime, the flash from a 16" is not that noticable. Put a good brake (JP BC Comp, Miculek, etc) on it if you want a muzzle attachment. A brake will be quite effective on a 16".

The two best options to look for are a free-floated barrel (handguards don't touch it) and a good trigger.

-z
 
Ok, so how hard would it really be to assemble a lower receiver? What is required? Is it like a complex Lego ship? How much technical expertise does it require?
 
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