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Posted: 10/17/2004 8:45:13 AM EDT
Is this worth the $12?

Does it work?
Link Posted: 10/17/2004 8:48:58 AM EDT
some say ya

others say screw it; its not worth $12

i'm getting 1 just to find out for my self
Link Posted: 10/17/2004 8:53:33 AM EDT
For $12, I would have a stack of O rings, or D-fenders.
Link Posted: 10/17/2004 9:30:24 AM EDT
will any O-ring work?
Link Posted: 10/17/2004 9:34:56 AM EDT
There is a certain size that I can't remember, but someone here will know. For the horribly inflated price of 15 cents, its worth trying just to see how you like it.
Link Posted: 10/17/2004 9:42:12 AM EDT
I found an O-ring stuck to a lyman punch set, i threw it in and it "fits"

But if you can find the size and recommended material, I'd like that!

I just went and tested the extraction, and its very powerful, almost like an AK now.
Link Posted: 10/17/2004 9:46:57 AM EDT

I just went and tested the extraction, and its very powerful, almost like an AK now.

Isn't it interesting that such a cheap upgrade makes such a difference?
Link Posted: 10/17/2004 9:48:16 AM EDT
Yep, just go to the hardware store with your extractor and try out o-rings til you find one that fits right. The other junk on the market is overpriced.
Link Posted: 10/17/2004 9:51:02 AM EDT
Cool, so there's no specific material required? Like Buna-N, Nitrile, Polyurethane, or another type that is recommended?

I found this O-ring stuck to a Lyman punch. I think it was left over from the manufacturing process. About 3/16" ID
Link Posted: 10/17/2004 10:10:37 AM EDT
Get the Viton rings. They have very good heat and solvent resistance.
Link Posted: 10/17/2004 11:01:34 AM EDT
I couldn't find anything that said what material they're made out of... but I grabbed some -007 o-rings from the local hardware store's plumbing aisle.

I wanted Viton rings but I think I may have to order them on the 'net.
Link Posted: 10/18/2004 1:40:50 AM EDT
They are not needed in general. All you should need is a HD/Wolff extra power extractor spring, which will not melt under conditions the o-rings will.

I found a combination of HD spring and o-ring device would occasional cause a failure of the bolt to go into battery on the first shot when manually charged.
Link Posted: 10/18/2004 3:56:40 AM EDT

I did notice the extractor was very tight. It cut into the rim of the shell, but if you let the bolt slap back it should charge properly.
Link Posted: 10/18/2004 4:19:29 AM EDT

Originally Posted By AK_Mike:
They are not needed in general. All you should need is a HD/Wolff extra power extractor spring, which will not melt under conditions the o-rings will.

My feelings exactly...
Link Posted: 10/18/2004 4:23:28 AM EDT
[Last Edit: 10/18/2004 4:24:21 AM EDT by twl]
Okay, we at MGI are the manufacturers of theD-Fender.
I can shed some light on this subject, since we invented the whole concept from the beginning, and have tried all the methods.

First, any of the methods(D-Fender, O-ring, HD spring) will work at least in the short term.
They all will increase the extractor tension.

However, there are some other factors at play here, which led to the development of the D-Fender.
We tried every kind of O-ring, and after various numbers of rounds fired, they failed.
This was because the shape of the O-ring is not consistent with the pressure of the spring on one side being greater than the other side, due to the nature of coil springs.
When the O-rings failed, they "squished" and broke, and would tend to migrate into an area that would cause the gun to tie-up.
This testing led to the development of the wedge-shaped profile of the D-Fender, and also to the D-shape, which some seem to think is not significant. I assure you that long term testing says it is.
The HD spring also works, but like any spring, it is subject to loss of tension from cycling and heat.
The D-Fender does not have any loss of tension from cycling or heat, and will not "squish", melt, break, or tie-up the gun, even after many thousands of rounds fired.

So, basically it is up to the user. Buy a number of the other kinds of devices over the life of the gun, or one D-Fender. Hopefully the failures of the other devices won't occur at a very inopportune moment when you are defending your life.

They will all work.
It is simply a matter of "how long", and what happens when they fail.

As the inventors of this extraction mod concept, we have done more testing, and have more experience than anyone on this subject. We hope to provide the important information, as well as the most reliable performing product to do this task.
Link Posted: 10/18/2004 4:34:45 AM EDT
I opted for the Wolff extra power spring as well. Think I got 3 in a package. Bet I won't have to buy any more extractor springs for the life of this gun.

Link Posted: 10/18/2004 5:02:06 AM EDT
[Last Edit: 10/18/2004 5:03:16 AM EDT by metroplex]
Wolff offers a lifetime warranty on their springs, so technically I'd just need 1 spring.

Does MGI or Armforte offer a lifetime warranty on the D-ring or D-fender? Is the Counterpoise D-Ring the same as the D-Fender?

How strong is the extraction on an AR15 generally speaking? If I remembered correctly, the M16 would spit out the shells in a neat pile back and to the right of the shooter. With just the Wolff spring, my shells are farther back and farther to the right. The RO complained about it hitting other shooters.
Link Posted: 10/18/2004 11:02:47 AM EDT
[Last Edit: 10/18/2004 11:05:46 AM EDT by twl]
The Armforte Counterpoise D-Ring and MGI D-Fender are the same product.
We at MGI make all of them.
The MGI is the current unit, and the Armforte stuff is no longer made.
No difference in them, it's just that Armforte is now absorbed into MGI,and all the products now have MGI names.
The Counterpoise has been superceded by the new MGI Rate/Recoil Reducing buffer(RRB).
The D-Ring is now available separately as the D-Fender.
The Adjustable Gas Tube is now available separately too.
All these products have their initial development roots in the old Armforte Counterpoise system which was developed jointly in a partnership between Mack Gwinn(MGI) and Jim Sullivan( associate designer of the AR15) as a way to incorporate increased controllability, recoil reduction, reduced muzzle climb, and increased reliability to the AR15/M16 carbine system.
Yes, they are warranteed for life to the original purchaser.

The D-Fender adds 4x the extractor tension, compared to stock extractor spring.
It is primarily used on carbines or shorties, which are known to have extraction difficulties due to high pressures in the cartridge case during the bolt opening cycle. The rifle-length systems do not have the same extraction difficulties, due to the fact that they have a longer gas system, and the timing of the bolt opening is delayed until the pressure in the case is far lower.
Link Posted: 10/18/2004 9:00:03 PM EDT
[Last Edit: 10/18/2004 9:02:19 PM EDT by AK_Mike]

Originally Posted By metroplex:

I did notice the extractor was very tight. It cut into the rim of the shell, but if you let the bolt slap back it should charge properly.

Sorry, but that was the problem - sometimes it wouldn't.

My springs held up longer under the heat of voluminous autofire better than the o-rings faired (even the DFenders I tried). However, that is not to say the springs will last forever either.

ETA: Shameless plug. I've had the adjustable gas tube and still have the MGI RR buffer. The MGI buffer ROCKS! Best I have tried among the systems out there to include the AAC system.
Link Posted: 10/18/2004 10:55:25 PM EDT
you should get a viton size #60 o-ring. you can buy them from McMaster-Carr in bulk (bag of 50) for under $10. Viton won't dissolve from standard cleaning solvents, and it has a higher temp rating.
Link Posted: 10/19/2004 4:18:51 AM EDT
[Last Edit: 10/19/2004 4:36:59 AM EDT by metroplex]
Are you sure about the sizing?

I thought it was -007 to be a better fit?

Mike: I loaded 100 rounds by manually charging them and they all charged properly. The extractor "claw" did have some brass marking on the top edge.
Link Posted: 10/19/2004 4:32:57 AM EDT
Link Posted: 10/19/2004 4:44:35 AM EDT
I'm wondering why Crane NWSC would even use an O-ring for an 18" barreled SPR - does it suffer the same extraction problems as the M4?
Link Posted: 10/19/2004 4:48:53 AM EDT
Link Posted: 10/19/2004 5:14:28 AM EDT
How long do these O-Rings last? I heard more than one positive comment about them being used out in the field.
Link Posted: 10/19/2004 7:01:32 AM EDT
Link Posted: 10/19/2004 8:01:38 PM EDT

Originally Posted By metroplex:
Mike: I loaded 100 rounds by manually charging them and they all charged properly. The extractor "claw" did have some brass marking on the top edge.

Experiences vary as does yours from mine. I shoot a half a case to a case each time I go, but only experienced the effect a few times - just enough to annoy me. When my M16 ran fine in all configurations without the ring on top of my Wolff springs, I decided I just didn't need it. If anything, I thought it was also a better way to go to prevent possibly ripping the heads off of a case. The most I have personally seen was really ugly brass marred up by an extractor that was too strong. Failure of the case head, messed up brass, and breaking an extractor sucks so I won't go there unless I have to. It's moot for me now because in the setups I would need one, I went with an LMT carrier or Fatboy gas tube, eliminating the need for such a strong extractor.

Bottom line, if you need it, use it, if not then don't. Better have one if you don't already have a good HD spring. There are cheaper alternatives to the mainstream products being offered.

I didn't throw mine (D-Fender and Crane O-rings) away, might need them someday.

Too stir the pot some more, now I see ads for a heavy duty SPRING INSERT. No, nothing to do with the black/red/white/blue "are they different or not" whole deal, these are made much heavier to positively provide increased extraction force. Another option, great...
Link Posted: 10/19/2004 8:20:06 PM EDT
[Last Edit: 10/20/2004 8:25:50 PM EDT by niceguymr]

Originally Posted By metroplex:
Is this worth the $12?

Does it work?

So where can I order one of these without having to spend 8 freaking dollars on shipping? It would be nice if you can pay actual US postage when ordering something like this, right? Otherwise, you end up spending $20 for a 2 cent piece of plastic.

EDIT: I found them on globaltactical.com, and with a few other small purchases, my total shipping charge was only $5. Thanks GTS.
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