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Posted: 4/16/2014 7:37:49 AM EDT
| Well, I've done about all I want or need to my 6920, with the exception of having read a great deal lately about the upgrade to the stiffer spring/o'ring/rubber insert for the extractor. I went ahead and ordered one from Bravo Company (really nice folks). Was wondering how many of ya'll use or consider this tweak a necessity? |
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For a current production 6920 it's nothing more than a redundancy.
You're going to be replacing identical parts. The issue is two-fold - the "extractor upgrade" consists of a five coil extractor spring, stiffer "bumper," and optional Viton O-ring than used to be use on M16-style rifles. The first is the fact that it took the military almost ten years to approve the ECP - Engineering Change Proposal by Colt to change this part in the M4 and M4A1 to improve reliability. Particularly before the Global War on Terror, the M4 was considered a "support" weapon, for use by truck drivers and armored vehicle crewman, etc. who had other jobs besides being riflemen, but needed something more powerful than a pistol. Yes, they were in use by SOF and some airborne units as well - but they were considered a low density weapon system and low priority, and the reliability was considered "acceptable." Needless to say, it was not to SOF, and they developed the O-ring and improved extractor parts set for the SOPMOD program to improve the reliability of their M4A1s. In the meantime, Colt was pushing to have this change made in the M4 and M4A1 spec, but the military did not want to bother, and it took until around 2005-ish for them to finally accept Colt's ECP and issue and have all new M4s come with the improved spring and bumper, which PEO Soldier hailed as a triumph of their organization for looking out for the soldier and improving the reliability of the M4. 
Eventually, Colt got approval to make the carbine extractor parts components standardized for all M16s and M4s - while it might not be needed in rifles, it doesn't hurt - and this streamlined both the production and military supply system, as well as preventing the accidental installation of rifle parts in carbines, much like the "F" marked FSB. The second element to this "issue" was the fact that many commercial reverse-engineered AR-style rifles and carbines continued (and some may still be) using the older rifle parts in their commercial carbines, even after the ECP to the M4/M4A1. Like the military, they figured the failure rate was "low enough" and there was no real need to change what they were doing and incur additional manufacturing costs. Because of this, many commercial non-Colt rifles "needed" this extractor upgrade, hence the proliferation of kits like the BCM, and people buying a bunch of O-rings, and the "D-fender" - it became "cheap insurance" to simply recommend if you weren't sure about your extractor parts, to just throw an "upgrade" kit in, and not worry about - to a certain extent, still good advice now. On the other hand, on a modern production 6920, and by modern production, pretty much any 6920 manufactured from at least 2006 and on, it will have the correct components - a quick way to check is to make sure that the "bumper" is black, not blue - this works with Colts - though some commercial manufacturers did use black "rifle-strength" bumpers. The moral of the story being - install the O-ring if you feel like it, and keep the rest of the parts as spares if you'd like, but I wouldn't bother replacing the Colt parts with the BCM parts immediately "just for the hell of it." A better option might just be to buy a stripped BCM extractor and pin as well, and go ahead and assemble them into a complete extractor assembly, and if you ever have an extractor problem or your extractor break, you can just "drop-in" a replacement and not worry about fiddling with moving/removing and installing little rubber pieces and springs. ~Augee |
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I have a few old parts that I used for new builds that would not work with the extractor donut. That was rather irritating. So it you use the new springs use the extractor donut. If you have the "old", was new to me, M4A1 upgrade springs (early 2000's) bronze colored spring with black insert they do not seem to work well with the extractor donut. In fact when I put the donut in with the bronze color springs they would not fully chamber a round (would not snap over extractor groove).
So when installing different parts: test fire. |
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Quoted:
For a current production 6920 it's nothing more than a redundancy. You're going to be replacing identical parts. The issue is two-fold - the "extractor upgrade" consists of a five coil extractor spring, stiffer "bumper," and optional Viton O-ring than used to be use on M16-style rifles. The first is the fact that it took the military almost ten years to approve the ECP - Engineering Change Proposal by Colt to change this part in the M4 and M4A1 to improve reliability. Particularly before the Global War on Terror, the M4 was considered a "support" weapon, for use by truck drivers and armored vehicle crewman, etc. who had other jobs besides being riflemen, but needed something more powerful than a pistol. Yes, they were in use by SOF and some airborne units as well - but they were considered a low density weapon system and low priority, and the reliability was considered "acceptable." Needless to say, it was not to SOF, and they developed the O-ring and improved extractor parts set for the SOPMOD program to improve the reliability of their M4A1s. In the meantime, Colt was pushing to have this change made in the M4 and M4A1 spec, but the military did not want to bother, and it took until around 2005-ish for them to finally accept Colt's ECP and issue and have all new M4s come with the improved spring and bumper, which PEO Soldier hailed as a triumph of their organization for looking out for the soldier and improving the reliability of the M4.
Eventually, Colt got approval to make the carbine extractor parts components standardized for all M16s and M4s - while it might not be needed in rifles, it doesn't hurt - and this streamlined both the production and military supply system, as well as preventing the accidental installation of rifle parts in carbines, much like the "F" marked FSB. The second element to this "issue" was the fact that many commercial reverse-engineered AR-style rifles and carbines continued (and some may still be) using the older rifle parts in their commercial carbines, even after the ECP to the M4/M4A1. Like the military, they figured the failure rate was "low enough" and there was no real need to change what they were doing and incur additional manufacturing costs. Because of this, many commercial non-Colt rifles "needed" this extractor upgrade, hence the proliferation of kits like the BCM, and people buying a bunch of O-rings, and the "D-fender" - it became "cheap insurance" to simply recommend if you weren't sure about your extractor parts, to just throw an "upgrade" kit in, and not worry about - to a certain extent, still good advice now. On the other hand, on a modern production 6920, and by modern production, pretty much any 6920 manufactured from at least 2006 and on, it will have the correct components - a quick way to check is to make sure that the "bumper" is black, not blue - this works with Colts - though some commercial manufacturers did use black "rifle-strength" bumpers. The moral of the story being - install the O-ring if you feel like it, and keep the rest of the parts as spares if you'd like, but I wouldn't bother replacing the Colt parts with the BCM parts immediately "just for the hell of it." A better option might just be to buy a stripped BCM extractor and pin as well, and go ahead and assemble them into a complete extractor assembly, and if you ever have an extractor problem or your extractor break, you can just "drop-in" a replacement and not worry about fiddling with moving/removing and installing little rubber pieces and springs. ~Augee I wish I had a straw that could siphon some of the info you posses. 
Will |
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Quoted:
If Augee if I understand you correctly, issued M4A1's (SOF and Big Army) all use the newer black insert, no donut and the copper extractor spring? As far as I know, though I'm not an armorer, Crane or otherwise - the factory part is the "correct" part. My understanding is that the "O"-ring is no longer a push - if a carbine is going through rebuild and they have one on hand and/or its requested, they can put one in, but there's no more requirement to install them "across the board." From the sounds of it, the extractor issue has largely been "licked" in the factory configuration. ~Augee |
| Extractor springs and inserts have been evolving for years. The color of each helps identify which one is in place - in a MIL-SPEC environment, at least. The "Crane O-Ring" is a fix for a specific problem in a specific M16 variant: the M4 (and probably more the M4A1 than the straight M4). It provides even more stiffness to the pressure placed on the tail of the extractor than the stronger spring and stiffer insert provide, which helps prevent deterioration of performance in high use/high temperature situations. For Joe Civilian, it's just a fancy gadget. |
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