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Posted: 4/17/2014 1:10:52 PM EDT
| Was out shooting with a buddy and after I showed him how to clean his S&W M&P Ar. I have a Colt LE6920. When I broke down the extractor, his had an oring around the extractor spring??? Never seen that before. My Colt did not, My bushy did not. Nor have I ever seen that. Is this an S&W thing only??? Or am i missing oring I never noticed before on my Ar's? |
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New out the box. Been around for years for Smith? Or all? No. It's a military thing that was developed in response to malfunctions on FA M4's and M16's (failure to eject). I guess it's just become fashionable, and some mfr's are including it as a kind of marketing thing. It's almost totally unnecessary on a SA civilian gun, with one exception being in the case where an extractor spring has sagged, and there is no longer adequate extractor grip. |
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My point being is I thought all parts were exchangable with all parts on the AR platform? So if one has an oring and the other does not, which is right and can the oring be added or taken away with no issues? Any mil-spec extractor spring should extract properly for thousands of rounds. That said, variations in QC among suppliers, high round counts, extractors with poorly-formed or worn claws, or ammunition with dimensional variances can introduce FTE's. I'd offer the opinion that any extractor that *requires* an o-ring for reliable extraction is an out-of-spec, faulty extractor. Why mfr's now put them in what should otherwise be fully-functional, mil-spec uppers is beyond me. Well, not actually: if I was an mfr, and could add a $0.02 item that increased buyer confidence and added a few (perhaps hundreds) of sales per year.......why would I not do that? |
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As barrels have gotten shorter, cycling issues have cropped up. The Army technical data package (TDP) for manufacturing M16s and M4s was updated to include a new extractor spring insert (black), in place of the old one (blue).
The o-ring around the spring started as a commercial fix for failures to extract on short barrels, associated with opening up gas ports to cycle on weak, crap ammo causing extraction issues when you moved up to regular, hot milspec ammo loads. With a black insert and an o-ring, it's possible to run your over gassed carbine on a wide variety of ammo, but it does tend to be hard on the brass. The military only ever runs M855, basically, so military M16s and M4s get by just on the black extractor spring insert. |
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Quoted:
As barrels have gotten shorter, cycling issues have cropped up. The Army technical data package (TDP) for manufacturing M16s and M4s was updated to include a new extractor spring insert (black), in place of the old one (blue). The o-ring around the spring started as a commercial fix for failures to extract on short barrels, associated with opening up gas ports to cycle on weak, crap ammo causing extraction issues when you moved up to regular, hot milspec ammo loads. With a black insert and an o-ring, it's possible to run your over gassed carbine on a wide variety of ammo, but it does tend to be hard on the brass. The military only ever runs M855, basically, so military M16s and M4s get by just on the black extractor spring insert. Information is spot on, but just need to add a touch more to it. The blue or black inner inserts in the extractor spring was Colts markers for the tension off the extractor spring. The blue insert was a standard tension spring, while the Black insert is the marker for an extra tension spring for the M-4 rifles. With other manufacturers other than Colt offering extractor spring, is not longer safe to assume that the color of the spring insert is a true marker of the tension of the spring (other than if you get the extractor spring directly from Colt that still follows there own standard). Also, there is no difference in tension between a black or blue insert itself, and other than as a spring marker (if the spring is directly from Colt), the inserts sole purpose in the spring is to keep the spring from collapsing sideways. So having said this, it's no longer safe to say if your extractor spring has a black insert, it an extra tension extractor spring (other than if you have a rifle made of all Colt certified parts). As for what started adding the #60 O ring around a standard tension extractor spring, it kind of like the chicken or the egg discussion, since the first commercial sold items to do this was the D-fender (O-rings where being used before the D-fender came out, but not being sold as a branded item for this use), and then other company followed such by commercial offering the #60 O ring as part of upgrade package with stronger springs after the D fender hit the market. As for D fenders and O rings on standard tension springs, lets face it's, it a band aid to correct a problem elsewhere. If the rifle requires a extra tension unit (such as in the case that you are running heaver than 62gr ammo), then just a extra tension extractor spring with insert alone (without a O ring or D-fender) should be used. Using both a D-fender/O-ring and extra tension extractor spring together increases the tension of the extractor too much, and although such will keep the extractor from slipping off the case rim during the pull cycle, it cause problem on the feed instead. Hence the extractor tension is now so great that the extractor can not spring out to climb over the live round as loading to allow the bolt to lock up correctly. To sum it up, you will see myself and other suggesting that a O ring be installed for rifle break in. The O ring will last for about 500 rounds, and once the O ring wear out, either the rifle has self polished in chamber through live fire and cleanings to no longer required the O ring, or you have problems in the rifle that should be resolved instead (and not just throw in another O ring Band-aid as a permanent item/part on the rifle). |
| that little o-ring can cause problems in very cold weather. when it gets cold the rubber won't compress enough to allow the extractor to slip over the rim during the feed stroke, preventing the bolt from going fully into battery. solution is to simply remove the o-ring. probably not an issue for most people. |
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As stated, the M-4 extra tension extractor spring is for rifles that are running heaver than 62 grain ammo. The reason for this, this heaver bullet ammo uses slower burning powder, which increases the gas port pressure to the action, and the added spring tension to make sure that the extractor does not slip off the rim during the harder than normal pull.
If you need a O ring, or M-4 spring in any rifle running 55 or 62 grain ammo, you have a problem elsewhere in the rifle, and it should solved instead of Band-aiding with the extra tension spring or O ring. Also, I stated Rifle, and when you get into SBR's or pistols, then all bets are off due to the shorter barrel, and may indeed find that you might have to run the Extra tension extractor spring or O ring/D-fender as part of the norm. |
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