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Posted: 1/8/2006 11:39:00 AM EDT
[#1]
First, let me make the disclaimer that I am the factory rep for the MGI D-Fender.
I consider this the best product for extractor enhancement that is made today. I have in front of me right here, a letter from the Department of the Army, on official letterhead, dated May 7, 2001, regarding the US Military DTC Safety Confirmation of the D-Fender for use in combat. Memorandum to SOPMOD. I quote this letter directly, beginning at Section 3 below. "3. Background: USSOCOM Forces have experienced incidents of failure to extract/eject with the M4A1 carbine. Special Operating Forces are constantly seeking tailored variations of standard M4 Carbines that more closely match mission requirements. This has led to the development of the Special Purpose Receiver and Close Quarters Battle Receiver, which are variants of the standard M16/M4. Issues of reliability have occurred with each of the variants, however, extraction problems across the board have been greatly reduced with the addition of the elastomeric washer "D-ring" around the extractor spring, with no detectable negative impact in serviceability or reliability. 4. Test Performed and Results: a. Documented use of these rings has occurred at NSWC Crane over the last year in an attempt to develop the limits of their performance. b. Extensive testing of standard M4/M16 gun/barrel/ammunition combinations were performed by NSWC Crane Division as well as modified barrels and ammunition. c. These were tested at the temperature extremes, dust and "gun" related chemical compatibility. 5. Conclusions and Recommendations: The D-Fender "D" elastomeric rings/washers have been used extensively on three configurations of the M16 type weapons and have always been found to aide reliability, without negative effects according to the test data provided by NSWC Crane Division. A DTC Safety Confirmation is issued for the use of the D-Fender "D" rings on M4/M16 series weapons. ............. Signed Alan Yankolonis Chief, Tank Automotive Armaments Division Directorate for Test and Technology" My emphasis added in red above.(twl) |
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Posted: 1/8/2006 11:53:14 AM EDT
[#2]
I have a Dfender in my M16.. I have never had a FTE with this gun.
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Posted: 1/8/2006 11:57:44 AM EDT
[#3]
The Crane O-Ring is nothing more than a #4 O-Ring available for 35 cents at any hardware store. I use this is all my bolts and it works perfectly. Save the $10 on either unit and go to the hardware store.
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Posted: 1/8/2006 12:02:04 PM EDT
[#4]
I would think that the D-ring would be better than an O-ring just due to its shape alone. An O-ring gets pinched into the shape of a D when installed over an extractor spring anyway, so you might as well start with a D-ring in the first place to avoid stressing the ring. Who knows?
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Posted: 1/8/2006 12:09:35 PM EDT
[#5]
The D-Fender is designed not to bind and pinch and will last the life of your barrel. The O-Ring is not. Is piece of mind worth $13? I have nothing but praise fo rthe D-Fender.
I helped a guy fix a 7" barrel micro M-16 that would not go 10 rounds without failing to extract. The D-Fender made his gun function like a swiss watch. The proof is in the pudding, his $10,000+ toy works for him now. |
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Posted: 1/8/2006 12:16:56 PM EDT
[#6]
Personally, I prefer not to add extra parts if possible so I would try using either a SAW or Wolff extra power extractior spring by itself first.
I run only the Wolff extractor spring on my carbines and I've found no need use any additional parts even with Wolf  .One carbine is high milage with over 9500 rounds and the other is a newer mid-length with about 1500 rounds through it. As always, YMMV. As to your original question, I would say that the D-fender is the better product because it's actually designed for this task and it looks like it's pretty much indestructable. That being said it still looks like the Crane O-ring will do the job but it will need to be replaced sooner which shouldn't be an issue because costs a lot less too. If I ever needed one I'd would go with the D-fender. |
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Posted: 1/8/2006 12:38:31 PM EDT
[#7]
I went with the D rings b/c they are proven to something like 30k rounds. This means that it will not be the cause of a stoppage.
To my knowledge noone has put standard, or even Viton, O rings to this test. Am I wrong? Sam |
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Posted: 1/8/2006 12:44:23 PM EDT
[#8]
I know of more than a few O-Rings with that were replaced with new barrels around the 10K round mark. There are about 1000 CRANE SPR uppers that were built with O-rings installed. The D-Fender *might* be better because of its shape, but maybe about $1 better.
There is no arguing both work, and both are in use successfully in the field. Some things are worth spending the extra money for, and when you have $300 handguard on your rifle, $13 doesnt seem like much, but $1 for one O-Ring is all that is necessary. Folks think the .15 hardware store rings are the same. Buy a D-fender, CRANE issue O-ring, and the hardware store special. Put all 3 in your overn and turn up the temp 100 degrees at a time. The hardware store rings usually become a puddle around 300 degrees. |
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Posted: 1/8/2006 12:51:41 PM EDT
[#9]
This may be splitting hairs, but the composition of the issued Crane O-ring is different than MOST store-bought versions.
The store bought #60 O-ring is typically made of BUN-A, whereas the Crane variant is something different (name of material slips my mind at the moment). Suffice it to say, BUN-A is less resistant to heat and solvent. This is likely a non-issue with regular replacement of the part. Changing out the 10 cent O-ring every time you perform PM will prevent any issues from arising. The D-fender is also a good part, and I would not hesitate to use one of those either. Either of them are cheap insurance, and are a VERY good idea if you are running a short format gun (11.5 or 10.5 inch barrel). Tim |
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Posted: 1/8/2006 12:55:14 PM EDT
[#10]
Are there any other upgrades I can do to increase reliability? I'm getting the D ring but is there something else I could use?
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Posted: 1/8/2006 1:02:20 PM EDT
[#11]
See this thread for starters...  www.ar15.com/forums/topic.html?b=3&f=118&t=257301 |
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Posted: 1/8/2006 1:06:48 PM EDT
[#12]
A basic cleaning kit. These things are pretty darn reliable, and dont really require much special attention. Just be asfe, shoot and have fun 
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Posted: 1/8/2006 1:17:17 PM EDT
[#13]
I'm using Wolff extra power extractor spring for my SHTF gun and it runs fine. If I ever have any problems with it I'm going to use a D-Fender or O-ring which is always in my tool box. My other guns have Crane O-rings which I got from ADCO. |
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Posted: 1/8/2006 1:18:13 PM EDT
[#14]
I have a D-Fender on one carbine, and a Crane O-ring on another. They both seem to work as advertised. But then again, my carbines ran fine without them, too.
 I'll stick to the $1.00 insurance from now on. |
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Posted: 1/8/2006 3:59:38 PM EDT
[#15]
I know for a fact Steve (ADCO) gets his O rings the same place I do. Major Vince Jiga. Neither of us runs to True Value to buy the O rings we use. They are a composition that can take it. I don't sell them as such but they go into most of the custom uppers I build just for some extra reliability. Denny |
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Posted: 1/8/2006 4:15:53 PM EDT
[#16]
To guys who run the D-Fender or Crane O-rings:
Do you guys also run an extra power extractor spring? The reason I ask is from what I remember Crane Reliabilty Parts Kit #2 contains both extra power extractor springs and o-rings. So I assume Crane prefers to use both and more extractor tension good for reliablity. Is it possible to have too much extractor spring tension? If so what side effects might result by using both? |
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Posted: 1/8/2006 4:42:03 PM EDT
[#17]
I think the crane o-rings are made of a special vitton rubber that the space
shuttle seals were made out of or at least that is similar to what I have been told. |
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Posted: 1/8/2006 4:49:31 PM EDT
[#18]
So we shouldn't use them in freezing weather? Just kidding. (but couldn't resist the irony).I'm a big fan of the crane O-ring, and use it in my 10.5" AR (thanks again, Steve!) ... and I have no doubt that the D-fender works awesomely as well. Both designs seem proven and effective. |
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Posted: 1/8/2006 4:50:56 PM EDT
[#19]
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Posted: 1/8/2006 4:54:43 PM EDT
[#20]
I use both a D-Fender and a Wolff extra power extractor spring in my rifle, and have never had any problems with the combination. |
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Posted: 1/8/2006 5:13:51 PM EDT
[#21]
The only problem that I see using both is if you have a weak CAR recoil spring with some type of heavy buffer, the bolt may not lock all the way into battery because of the spring tension on the extractor. I had this problem last weekend on my SPR. I could not figure out why the round didnt fire. Everything looked good and the firing pin struck the primer. I talked to Grant and he told me that this may be my issue. I bought one of his new style recoil springs with a lot more tension. This solved the problem of the bolt not going into battery. I kept the wolf extractor spring and viton Oring. The rifle runs like a champ. |
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Posted: 1/8/2006 5:31:17 PM EDT
[#22]
So where does one get a D-Fender ring?
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Posted: 1/8/2006 5:49:11 PM EDT
[#23]
I have a D-fender and wolff extra power spring, and my AR flings brass into one nice pile.
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Posted: 1/8/2006 5:57:36 PM EDT
[#24]
i use the d-fender in all of my rifles with no extraction problems before or after install.
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Posted: 1/8/2006 6:20:16 PM EDT
[#25]
You may notice that I am the MGI factory rep. My contact info is in my signature line below. Happy to help. |
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Posted: 1/8/2006 6:30:16 PM EDT
[#26]
35 cents? I bought 500 of them off of Ebay for $5. I change them out a few times a year. If my life depended on my rifle daily, I would go with the designed for the cause version. It doesnt, so I dont. |
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Posted: 1/8/2006 6:46:30 PM EDT
[#27]
I have a D-Fender in my new middy (CMT bolt) with 250 rds. of Q3131 down it. Seems to do the job more than well enough. You can see where the extractor was on the case rim, but it hasn't been an issue yet and the extractor looks perfect. I think the use of both is a little overkill, IMO. I like the D-Fender because it's only $13 on something you'd trust your life to and considering how much the rifle is worth... it's probably the cheapest part on it. Also designed by someone who should know what they're doing.
You asked about other things to increase reliability...well, first off it's unusal for me to stray from the original design so for me to use the D-Fender is a stretch, but I also decided to go with a CMT "H buffer" for the added .8 oz. of weight. My brass hits the very front edge of the brass deflector half way up the case and flys off at 1:30 - 2 o'clock. I also am a believer in ISMI springs, so I got a David Tubb CS ISMI flat-wound recoil spring. I spared no expense in my build, and these are the only "extras" I added. Barrel is 4150 CMV and bolt is MP checked. You're favorite ARFCOM supporter should have the D-Fender...including the ones who replied to this thread. |
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Posted: 1/9/2006 1:57:53 PM EDT
[#28]
As a minimalist I did not go with the D-ring just b/c I thought it would be a good idea. One of my 11.5s had a severe case of dropped extraction about once or twice/mag dump. Another 11.5 - with lower round count - does not have this problem, so does not have a ring.........yet. The D ring is/was the only modification I made to the extractor on the problem upper. I have not had even one more failure to extract since doing so. We're talking about 3k rounds downrange with this particular upper since adding the ring. I doubt that adding the spring would cause a problem. But it was just not necessary. I haven't needed one for the 14.5s. Nor do I feel any need to use rings or HD springs with any full length gas system uppers. Sam |
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Posted: 2/20/2006 2:21:02 PM EDT
[#29]
Viton isn't rated for arctic use (only down to -10F).
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Posted: 2/21/2006 1:36:09 AM EDT
[#30]
I've looked at this again and I don't understand how the springs "wear out" when you're dealing with chrome-silicon or Wolff extractor springs, which are generally rated for compression cycles in the hundreds of thousands (i.e. 500,000 compression cycles). The extractor does not completely compress/relax the spring. Has anyone worn out their 4-coil CS extractor spring or their Wolff spring? The cheaper springs are more likely to lose their spring rate due to material fatigue since the coils are thinner (wire diameter plays a role in spring rate based on material choice).
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Posted: 2/21/2006 2:26:47 AM EDT
[#31]
There is no difference between the O ring that Crane had produced and the D-fender in the minds of the folks in the SOPMOD project. The O ring, like the Crane Carbine Stock were projects that they developed in house, that after development and testing, found that there were similar items off the shelf that did just as good if not better than what they developed in house.
The above info came from someone involved in the SOPMOD project that I served with in Panama. |
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Posted: 2/21/2006 7:09:29 AM EDT
[#32]
Crane knows the difference.
They know that the O-ring is not the equal of the D-Fender. Their response to us when reliability over time was brought up, was, "Yeah, but we can give out a handful of O-rings for a cheaper price." The truth hurts sometimes. Do you want to NEED a handful of O-rings to replace when they break? Or just one item that will last the test of time? Crane has bought thousands of D-Fenders. They have the test data. The cost was the overriding factor there, not the performance. We invented the idea, did all the initial tests on the O-rings(that we tried first, doh!), and then on the improved D-Fender shape. Since we invented this whole thing, and tried the O-rings first and they proved not reliable over long term, we HAD to go further to the D-Fender shape in order to provide the proper reliability for our boys in combat. We brought the D-Fender to Crane, and it tested perfect in all conditions and in all M16 series weapons. We have the US Gov't Safety Testing Certification. No failures. Believe what you want, but we are the originators of the concept, and know more about this idea than anyone else does. If you want the most advanced product for this purpose, and your life is on the line, then the D-Fender is the one you want. If you are just a range shooter, the O-ring should do just fine, as long as you change it out regularly. |
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Posted: 2/21/2006 7:15:34 AM EDT
[#33]
No kidding, what's $10 more to someone who has already made their mind up that they needed the added insurance already? Come on now...it's a one time cost. Hell, I even purchased a second D-Fender just in case.
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Posted: 2/21/2006 7:20:03 AM EDT
[#34]
Has NSWC experimented with as FEW parts as possible? I find it surprising that they would require the 1 piece gas ring, extractor insert, 4-coil CS extractor spring, CS ejector spring, AND the O-Ring all used at the same time. It would be more cost effective to use only the most vital parts.
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Posted: 2/21/2006 8:26:55 AM EDT
[#35]
How does the Armforte D-Ring compair to the MGI brand name D-Ring?
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Posted: 2/21/2006 8:29:41 AM EDT
[#36]
Question: Isn't it true that the D-Fender was designed for use with the blue insert extractor spring?
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Posted: 2/21/2006 8:34:49 AM EDT
[#37]
Armforte was the company that Mack Gwinn and Jim Sullivan were partnered in, and no longer exists. It is the same D-Fender D-ring as the MGI. After the Armforte, partners went their separate ways, Mack Gwinn formed MGI and the D-Fender product is now produced under the MGI name. It's only still called "Armforte" in the Brownell's catalog, because Brownell's can't seem to get their act together after 5 years to change the name to MGI. The D-Fender was actually designed to have no "insert" in the spring. The D-Fender increases extraction force by 4x, all by itself. |
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Posted: 2/21/2006 8:48:47 AM EDT
[#38]
If anyone has that much of a hard-on to increase extractor spring tension the D-Fender hands down is the best way to go. I personally don't like to deviate from the original design so *if and when* my extractor starts to act up I'll more than likey just replace the spring with something from Wolff.
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Posted: 2/21/2006 8:51:23 AM EDT
[#39]
Yeah! Quit messing around with what isn't broke, and leave the junk out of your gun. |
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Posted: 2/21/2006 10:39:43 AM EDT
[#40]
...so would you recommend removal of the spring insert all together, removal of the D-Fender, or change the spring out for the black insert spring in a mid-length carbine? Does this 4x extraction accelerate extractor wear? With blue insert spring and D-Fender, I am ejecting at 1:30 - 2:00 after bounding off the leading edge of the brass deflector. This is with enhanced carrier, "H" buffer, and ISMI recoil spring. |
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Posted: 2/21/2006 11:47:00 AM EDT
[#41]
tag
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Posted: 2/21/2006 12:42:31 PM EDT
[#42]
I would use the standard spring, with no insert, and a D-Fender. That's what I have in my gun, and I have zero problems with any extraction issues. |
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Posted: 2/21/2006 12:52:02 PM EDT
[#43]
I thought the spring insert was added to "greatly increase spring life" by acting somewhat as a "buffer". Will removal not have any negative effect on the spring itself?
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Posted: 2/21/2006 12:53:27 PM EDT
[#44]
I have used both the D-Fender & ADCO CRANE o-ring, both with zero problems. I only switched to using the Adco o-rings exclusively because they have proven themselves and only cost $1 each. I also inspect mine every time I clean my weapon and change them out if they show any wear. I would never trust a manufacturer claim that either one will "Out live your barrel". That sounds fishy to me.
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Posted: 2/21/2006 5:27:53 PM EDT
[#45]
I use the oring - threw the d ring out.
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Posted: 2/21/2006 5:33:56 PM EDT
[#46]
Any reason or are you just trying to show your ass? 
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Posted: 2/21/2006 6:36:01 PM EDT
[#47]
These threads always become an argument, or at least a difference of opinion. All I can say at this point is that we invented the whole thing, and if we hadn't brought the D-Fender to Crane in the first place, there still may not have been a resolution to the extraction issue in carbines, because Crane would have had nothing to try to copy. Whether people want to acknowledge that we properly understand this issue because we invented it, is up to them. I find it rather amusing that when it comes to other serious items that people want to use, and cost a whole lot of money, the standard response is, "If you are serious about your life, use the best part. Don't cheap out". But when it comes to a measly $12.95 for a critical part that has been designed specifically for this application, and has been proven by official US Military tests to keep the weapon reliable over the long term, some decide it's better to spend a dime instead, for something that was never designed or intended to work in this application. An O-ring is an oil seal. If you want to make it into an extractor enhancement device, then that is your business. Don't blame me when it fails. I told you about it. By the way, we don't make any "claim" about it lasting longer than your barrel. We cite the tests at Crane, during which they repeatedly tested the D-Fender past 30K rounds in an attempt to make it fail, and it never failed. The US Gov't issued certificate states that it works in all environments, and certain chemical conditions, and it ALWAYS improved extraction reliability in VARIOUS CONFIGURATIONS OF M16 TYPE WEAPONS and WITHOUT ANY NEGATIVE EFFECTS. We rely on the US Government documents, and Crane NSWC test results to back up our statements of performance with this product. |
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Posted: 2/23/2006 12:16:14 PM EDT
[#48]
I got my D-Fenders today and they're not blue, but rather a black/gray color.
I was hesistant to lay down $10 for one, but if they're expected to last/outlast the life of the barrel, I might as well give it a try. |
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Posted: 2/23/2006 12:25:46 PM EDT
[#49]
The D-Fenders haven't been blue in YEARS from what I remember...the blue insert I was referring to was the one in the spring itself.
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Posted: 2/23/2006 1:21:13 PM EDT
[#50]
I have never heard of a true D-Fender failing or anyone who owns one being dissapointed with it. That is the true test of a product.
Beware of knock-off 'D' shaped extractor enhancers. They are soft and failure prone. Make sure your's says MGI on the package. The real thing is very firm when you pinch it, the phony is squishy as hell. |
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