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Posted: 11/23/2008 9:46:08 AM EDT
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Anyone use one of these D-Fender D-ring extractor rings?
Worth it? Work Well? Snake Oil, LOL? Is there a better way? http://www.brownells.com/aspx/NS/store/productdetail.aspx?p=9949&st=defender&s=25952 Thanks J- |
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They work just fine. It's a lot cheaper to just use a little o-ring though.
I can't remember the correct size o-ring though. I'll go dig around and see if I can find the ones I have. At any rate, you can get a bag of them at McMaster-Carr for about the price of one d-fender. |
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Not needed in my opinion, but I do replace all my blue extractor buffers with military black buffers and I replace the stock extractor springs with the brownells Chrome Silicone springs. I have used the D-ring in the past but when hunting I like to use the forward assist to quietly chamber a round. With a D-ring or O-ring thingy the FA becomes useless, the extractor will not pop over the rim of the shell without alot of force.
The only time I would consider the D-ring is if my gun was having problems extracting. But I would make sure my extractor, ejector and springs were good first. http://www.brownells.com/aspx/NS/store/ProductDetail.aspx?p=20892&title=AR-15%20EXTRACTOR%20BUFFER&s=45796#45796 http://www.brownells.com/aspx/NS/store/ProductDetail.aspx?p=22091&title=AR-15/M16/M4%20SPRINGS&s=47792#47792 |
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I've used both the d-fender and the o-rings and had no problem with the forward assist... not that I needed the assist to start with.
The o-rings at mcmaster-carr are the "Viton" type and the size is either 006 or 007. I belive it's the 006, but even if you buy both sizes, the total won't come to more than $15 or so for the entire order, and there are 75 of them per bag. Get some. They work, and they're cheap. http://www.mcmaster.com/ edited to add: Looks like they're 50 per pack now, and the ones you're looking for are Viton AS568A Dash Number 006 (or 007) "military specification". $4.82 per pack. |
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Quoted:
I've used both the d-fender and the o-rings and had no problem with the forward assist... not that I needed the assist to start with. The o-rings at mcmaster-carr are the "Viton" type and the size is either 006 or 007. I belive it's the 006, but even if you buy both sizes, the total won't come to more than $15 or so for the entire order, and there are 75 of them per bag. Get some. They work, and they're cheap. http://www.mcmaster.com/ edited to add: Looks like they're 50 per pack now, and the ones you're looking for are Viton AS568A Dash Number 006 (or 007) "military specification". $4.82 per pack. Thanks for the info, I'll pick a pack up as spares. |
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edited to add: Looks like they're 50 per pack now, and the ones you're looking for are Viton AS568A Dash Number 006 (or 007) "military specification". $4.82 per pack. A careful measuring of my o-ring makes me think it's the "006" variant. Part #1201T16. |
Are we certain that Viton is the correct material? Viton will release Hydroflouric acid if it gets too hot (300 to 400F depending upon whom you believe). There has to be a lot of hot gas in the vicinity of the extractor. If you get hydroflouric acid on your fingers the cure includes amputation!
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edited to add: Looks like they're 50 per pack now, and the ones you're looking for are Viton AS568A Dash Number 006 (or 007) "military specification". $4.82 per pack. A careful measuring of my o-ring makes me think it's the "006" variant. Part #1201T16. You are correct. I finally got around to pulling one from my bolt and it _is_ the 006. |
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Are we certain that Viton is the correct material? Viton will release Hydroflouric acid if it gets too hot (300 to 400F depending upon whom you believe). There has to be a lot of hot gas in the vicinity of the extractor. If you get hydroflouric acid on your fingers the cure includes amputation!  If you'll go to the archives and do a search on this subject, you'll see that a lot of people have been using these for a long time now with no problems whatsoever. Besides, they're marked "military specification" for a reason. |
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If you'll go to the archives and do a search on this subject, you'll see that a lot of people have been using these for a long time now with no problems whatsoever. Besides, they're marked "military specification" for a reason. Clearly. However, people have been using viton seals in car engines for years "with no problems whatsoever" but....Hydroflouric acid from seal breakdown after a temperature excursion or fire is a known hazard for mechanics and rescue personnel. But it's good to know that there have been no incidents. FWIW- Wasn't Agent Orange "mil-spec"? |
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One of my shorties had a bad case of dropped extraction. All it needed was a D-ring. The ring has lasted long enough for me to pooch that barrel. It's slated for another bolt and barrel. My understanding is that the D-ring has been tested out to many tens of thousands of rounds by MGI.
I've also used the less expensive O-rings. Functionally, they do as well. I can't speak to their longevity. The other way to go is with an extra-duty extractor spring. I've used one and it works just fine. Again, I can't say how long the spring would last. But I have broken extractor springs. My best guess would be that a D-ring would outlast several extractor springs. Be wary of using both a xtra power spring and a ring.......can be too much of a good thing and the extractor may not get over the rim. BTDT. Dropped extraction is pretty much a non-issue with full length gas systems. I spoke with Mack Gwynn about this a few years back and he says that extractors lift even with the full length gas system - but not enough to cause dropped cases. With carbine systems - whether or not I have dropped extraction - I always install a D or O ring, or a xtra power spring. Sam |
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The Crane O ring is made of a specific type of material that underwent a whole bunch of testing, and does not break down under extreems of heat. The D-Fender is the only Commercialy available product of this type, and has been approved for use in USSOCOM weapons as not just a subsitute, but an actual equal to the Crane O ring. If you order the extraction reliability package from Crane you might get the O ring, or you might get the D-fender, there is no choice, just what happens to be in stock when the kits are assembled.
If you just use any old O-Ring from the hardware store you could end up with the bad chem reaction that other posters have spoke of, or you could just introduce melted plactic/rubber into your bolt, which has been known to have adverse effects on the functioning of the weapon. |
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Some people worry too much.
Others are trying to sell overpriced stuff. Others are practical and go with the same o-rings people have been using for years now with no problems. You guys can talk all day every day for weeks if ya want. The truth is that the mil-spec o-rings at McMaster-Carr are just fine. Using anything else is throwing your money away. Enough said. I'm done with the subject. Let the "internet experts" talk it to death now. 
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Some people worry too much. Others are trying to sell overpriced stuff. Others are practical and go with the same o-rings people have been using for years now with no problems. You guys can talk all day every day for weeks if ya want. The truth is that the mil-spec o-rings at McMaster-Carr are just fine. Using anything else is throwing your money away. Enough said. I'm done with the subject. Let the "internet experts" talk it to death now. When your cheap ass O ring melts, and fuses your extractor into the open position, I am reserving "I told you so's" Some folks use tacpoints and Ace Hardware o rings, others use Aimpoints and D Fenders. The unfortunate side of all of this is that the naysayers might not make it back to report how bad their choices were, and their "just as good As" gear got themselves into a situation where their gear couldnt get them home 
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