Finally splurged on an AR-15 - questions


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another okie
November 11, 2003, 08:07 PM
Well, I decided I had to have one. I bought a Bushmaster A3 with a 20" barrel. I had earlier posted a thread asking about books on assembly and cleaning, but I see now (as one poster had said) that the Bushmaster instruction book is more than ample. So far I've just been practicing assembling and dissassembling it. Some of those pins are tight!

Questions:

1. I can completely dissassemble with a cartridge, except for the extractor pin. I can push it part way out, but it takes a pair of pliers to take it the rest of the way. Is this normal, or will it loosen up, or is there some trick I'm missing?

2. What's the best sling? The factory sling is OK to carry it over your shoulder, but is there a good one that allows you to carry it in front and lift it easily to the shoulder?

3. I have an M-3 light I bought for my Glock 17. What's the best mount? I'd like to be able to put the light on my AR as well. (Already have a mount made by Streamlight for my Remington 1100.)

4. Why is there a "drain" channel in the rear of the stock? What's supposed to drain out of there?

5. Is there a good book on the history of the AR? I'm a compulsive learner once I start on something, and I want to know as much as possible about it.

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Jhaislet
November 11, 2003, 08:23 PM
Check out AR15.com (http://www.ar15.com) .

Variable1
November 11, 2003, 08:50 PM
Lets see if I can help out on this one.

1.) The extractor pin will losen up and will be easier to remove.

2.) I am biased, :D but I like the CQB Solutions SOP and CST 3 point slings.

3.) You can add a mount to your handguards, or to the front sight tower. Lots of options on that one. The Streamlight mount works well and is priced right. Plus it allows the light to be mounted in a easy to reach location.

4.) That is so water/oil/etc can drain out of the stock. If it was raining, or you had to cross water, it would collect in the buffer tube. Not a very pretty sight when you tried to fire of that first round:what:

5.) I believe D. Long has a couple of good AR books. Also The Black RIfle. Best to go check on AR15.com.

ShaiVong
November 11, 2003, 09:28 PM
This may sound dumb, but try and push the extractor claw assm. inwards twords the firing pin. Like your squeezing the bolt between your thumb and finger, and pushing the extractor inward.

If i squeeze the extractor and compress the spring, the pin will just about fall out, and it was like that brand new. Just need to take the tension off of the pin.

Jhaislet
November 11, 2003, 09:36 PM
I had my bolt disassembled earlier today, and noticed a lot of wear on the firing pin retaining pin (not the cotter pin, but the actual round pin with the square top and horizontal circular hole through its shaft).

The wearing appeared in a C shaped pattern and the wear pattern which made up the "C" was very deep (maybe between 1/16-1/32 of an inch). Is this normal? The bolt has about 1500 rounds through it and all was either lake city M193 or Winchester Q3131A (strictly 55grn mil-spec M193 ball).
The rifle is a stock Bushmaster 16" HBAR w/M4 profile.

Kharn
November 11, 2003, 10:00 PM
Jhaislet:
"not the cotter pin, but the actual round pin with the square top and horizontal circular hole through its shaft"
I believe you are referring to the cam pin.

If you're in doubt about it, replace it. Its a lot cheaper to buy a new cam pin than a new rifle (if the cam pin is missing, the bolt will not cam into the closed position and the rifle will fire as a blowback, not a good thing for .223), they're like $3.

Kharn

Jhaislet
November 11, 2003, 10:08 PM
Bingo, its the cam pin. My mind blanked out for a sec. Could something else be causing the extended wear pattern I've observed? I've broken down my fair share of military M16's, all of which had many thousands of rounds through them, yet I never noticed such distinctive wear on the cam pin.

Jack19
November 12, 2003, 05:57 AM
GG&G (http://gggaz.com/products/uwwsystem.php)

These folks carry everything you will ever need....and then some. :D

And, I'll second Variable on his recommendation of CQB Solutions' slings.

ARperson
November 12, 2003, 10:41 AM
Just an FYI, you don't have to disassemble the bolt itself for every cleaning.

Steve Smith
November 12, 2003, 10:43 AM
Cam pin wear is not abnormal. It is usually something you replace with every rebarrel.

BillL223
November 12, 2003, 10:49 AM
Cam pin wear is normal but 1/32 "- 1/16" @ 1500 rounds is excessive. I suggest you increase lube in this area.

gun-fucious
November 12, 2003, 01:57 PM
the cam pin runs in a slot in the upper

better look there for wear too

dbshabo
November 13, 2003, 12:39 PM
Listen to Kharn, if the cam pin has undue wear on it, replace it pronto.
I'll also put in a vote for the CQB Solutions 3 point sling. I love mine.

Shabo

Steve Smith
November 13, 2003, 12:53 PM
Re-read the post, yes, 1/16" is excessive. Increase lube as Bill said.

ShaiVong
November 13, 2003, 04:48 PM
the bolt will not cam into the closed position and the rifle will fire as a blowback, not a good thing for .223

Why? Will it blast back with tons of excessive force? Enough to cause major damage?

Frohickey
November 13, 2003, 05:11 PM
When you get a new upper, is it also a good idea to have a brand new bolt for it? Meaning that bolts should not be swapped between different uppers?

What happens if you have water in the buttstock and you shoot it?

Steve Smith
November 13, 2003, 05:14 PM
The bolt must be locked to hold in the extremely high pressure that is inside the chamber. You COULD have a blowback operated rifle, but the recoil spring and the mass of the bolt would be so great that very few could operate it by hand or carry it comfortably.

Consider this: Most quality pistols use a blowback action for calibers up to .380 max. Some companies like Bersa use a locked breech for the .380, and Kel-Tec uses a locked breech for a .32. The guns are light and easy to operate. Now, conversely, Hi Point uses blowback for handguns up to .45 acp. Have you felt one? It feels like a brick on top and the recoil spring is stiff too. A blowback action uses the mass of the bolt and the weight of the spring to hold the breech closed until the pressure drops to a safe level. A locked breech uses a mechanical lock to delay the opening in order to accomplish the same thing. In the AR, the gas forces the carrier to move backward away from the bolt, which in turn makes the bolt turn and the lugs disengage the barrel extension. The carrier and bolt continue to move backwards but the pressure has decreased substantially by the time the lugs disengage. In fact, the pressure does not even begin to affect the unlocking of the bolt assembly until the bullet is almost at the end of the barrel since the gas port is near the end.



Bolts should technically not be interchanged, but a quick test for headspace can get you in the clear.


I don't believe shooting an AR with a buttstock full of water would be "bad." This is what I believe would happen:

Rifle fires.

Gas pressure surges in gas tube and bolt carrier begins to move backwards, but water does not compress so the buffer cannot move backward at the normal rate of speed.

A tiny, high pressure squirt of water leaps from the rear of the buffer tube.

As a guess, I'd say that the carrier makes it back about 1/8" before the pressure drops again and carrier movement stops. Not enough to make the bolt lugs shear.

In the mean time, gas pressure surged in the tube but there was no release, so I think that the tube will rupture under the handguards.

Bullet strikes target.

Case has to be manually extracted, perhaps with great difficulty since the bolt has turned slightly.

A new gas tube and perhaps a new bolt, and an inspection of the barrel extension would be in order.

ShaiVong
November 13, 2003, 09:50 PM
A blowback action uses the mass of the bolt and the weight of the spring to hold the breech closed until the pressure drops to a safe level. A locked breech uses a mechanical lock to delay the opening in order to accomplish the same thing.

So how do higher caliber handguns like my G22 lock the breech shut until a safer opening pressure has been achieved?

Steve Smith
November 14, 2003, 10:13 AM
You own it and you don't know how it works???!!!


Ok, if you notice, the rear of the barrel must drop away from the slide in order for the slide to move rearwards and for the breech to begin to open. The time that it takes for the rear of the barrel to drop and clear the slide, and the time it takes for the barrel lug to travel along the cross pin (under the barrel) is actually engineered so that the pressure has dropped before the breech begins to open.


No more guns for you until you take a mech engineering course!

Kamicosmos
November 14, 2003, 04:15 PM
Hey Steve, I'll assume there is sarcasm intended when you say:

I don't believe shooting an AR with a buttstock full of water would be "bad."

and go on to describe the total failure of the rifle, what with the gas tube exploding, and the case being difficult to extract by hand.

It may be repairable, and sure maybe that first shot hit the target, but I would guess that the rifle being practically destroyed would be 'A Bad Thing.' Especially in a combat situation where a second shot is most likely needed, and making those kinds of repairs in the field would be next to impossible, even when not in direct combat.

And all combat mentions aside....I don't want my rifle to suffer that kind of failure if I can avoid it! :)

Steve Smith
November 14, 2003, 04:23 PM
I would hardly consider a ruptured gas tube to be catastrophic to the entire rifle. In combat, yes, but generally speaking, not at all. Easily fixed. That's why i said I wouldn't call it "bad."

In fact, I just edited my post where it said "major damage" because the more I wrote about it the less catastrophic it seemed to be. I forgot that I'd written that at the beginning.

And all combat mentions aside....I don't want my rifle to suffer that kind of failure if I can avoid it!

Which is why the drain hole is there! :)

ShaiVong
November 14, 2003, 04:35 PM
No more guns for you until you take a mech engineering course!

Awww jeeze! Let me focus on getting my Elec. Engineering degree first!

If you let me get a couple more I promise to look really close at them before I pull the trigger! :neener:

Then what happens to those guys who swim to shore with M4'? Or who parachute into the water with them.. Do they just use MP5's for water insertion? Are they blowback

Steve Smith
November 14, 2003, 04:41 PM
No, the water runs out the drain hole. 'Bout the only way to keep it full is to keep the muzzle pointed straight down so that none of the water runs out.

Keep in mind, I haven't actually DONE this, but logically that's what would happen. I don't think the drain hole is large enough to release pressure at the same rate that it wil build when the gun was fired.

As a matter of fact, an MP5 IS essentially blowback. It is a mechanically delayed blowback, just like it's bigger brother the HK91. A set of spring loaded rollers lock into place when the bolt closes. They significantly delay the opening of the action. I don't think this is even a consideration for water assaults, though. The M16/AR tube can drain pretty quick I imagine. Besides, you don't need to drain all the water out. Perhaps 1/2 to 2/3 of it for full operation.


BTW, workin' on my EE as well.

fight4yourrights
November 14, 2003, 09:47 PM
1. I use the Firing Pin Retaining Pin; ie: "cotter pin" (technically it's not) to push out the extractor pin

2. Giles 3 point tactical, Eagle, etc... Depends on how you want to carry it.

3. Somebody makes an M3 mount, but I dont' have that info

4. as mentioned, sater

5. THE BLACK RIFLE is a great book on the history of the AR15/M16/AR15

BTW - your best source for informaton, besides/instead of AR15.com is The Maryland AR15 Shooters Site (www.md-15.com). A lot more reviews and technical information that AR15.com has now.

TechBrute
November 15, 2003, 12:15 AM
Here (http://www.gggaz.com/products/m3illumrifle.php) is a good mount for the M3 light on a non-railed fore-end.

Do not attempt to put the M3 on a standard picatinny rail. The picatinny rail is larger than the "universal" rail that the M3 slides on to, so it will be tough to slide on and then loose when you put it back on your handgun.

Here (http://www.gggaz.com/products/m3ti.php) is an adapter so you can use your M3 on a railed fore-end like the ARMS SIR system or the KAC RIS/RAS.

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