Since I purchased my gun used I cannot tell you what modifications may have been made by prior owners however it doesn't appear as though the gun had been touched in any way prior to my ownership.
The issue: During routine cleaning of the bolt, specifically the extractor, I would observe that shaking the bolt or the slighest push of the roll pin on the extractor would release it from the bolt. The extractor spring seemed very weak, even smaller than spec. The gun has operated flawlessly in this condition, brass is extracted with enough zing (3 - 5 feet) however it did bother me to think that the roll pin was just loosly fitted.
The fix causing another issue: I had read good reports from AR15 owners on the BCM extractor spring upgrade kit (spring/insert/oring) and decided to have one installed for me recently. The guy doing the install (he was doing a trigger job for me and offered to put the spring in for me, I didn't get a guy to do just the spring install :p) wrestled with the extractor and roll pin for 20 minutes every so often muttering "I haven't ever had this much trouble getting a sping set". So I get the gun home and attempt a function test with this new extractor spring kit and JAM! The extractor was so tight it couldn't go over the rim of the case and the gun couldn't chamber a round.
The fix to the original issue part 2: I went to cheaper than dirt and bought a DPMS roll pin and spring kit (20 bucks total). The spring appeared more stout than the original and the roll pin had a tighter fit. I would say that basically I went back to stock and the rounds chamber and extract in my function testing.
I have done some research after the fact on the BCM upgrade kit and cannot find anyone with a similar story to report.
Are any Alexander Arms overwatch owners using the BCM extractor springs?
How about those using the Alexander Arms Grendel bolts, any reports of loose roll pins?
Thx,
BB
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BB, I've never had that issue with AA bolts, having used about 8 or 9 different bolts, in 6 different guns.
Interesting.
You seek escape from pain. We seek the achievement of happiness. You exist for the sake of avoiding punishment. We exist for the sake of earning rewards. Threats will not make us function; fear is not our incentive. It is not death that we wish to avoid, but life that we wish to live. - John Galt
I have seen this as well. If you try to place one of the O or D rings as an "enhancement", it often produces the results you experienced. There's a lot to be said for a quality, standard Milspec spring and buffer insert, balanced with a quality ejector spring and ejector made to the appropriate dimensions for the caliber.
Not all parts are the same. I could go on endlessly about parts that we think are good, and aren't.
Just to clarify we left the oring off the BCM spring and it was still too tight.
I will fire some rounds through the gun on Wednesday to see if it checks out with the DPMS spring and roll pin, should be fine.
BB
I've usually found that if the extractor spring is so tight that you can't move the extractor with your finger using some force, it probably will do what yours did. I've tried some of those extra power springs and "D" rings, that were sent with an article basically saying that your son will die if he doesn't have this piece of equipment. They did the same thing. Guys that use them in short-barreled full autos often shave the "D" ring in half to get them to work, if I remember correctly.
I standard Milpsec spring and insert seems to work best for me.
Just use a 5 coil spring with black insert for carbine and rifle gas systems. You should be using a "Solid" pin in your extractor/bolt not a "Roll" pin
My error in terminology, it was initially a loose fitting solid pin.
Thx,
BB
I have a totally original early 80s Colt Sporter AR with very low round count (<500) and I like to use that rifle as a comparison to my new AR clones. one thing that is readily apparent is that the colt uses a pretty soft extracator spring. The extractor can easily be flexed outward using your fingers. The same cannot be said on my grendel. The colt has always cycled perfectly with any ammo in it, too.
Colt has the benefit of years of initial research from Armalite, as well as years of R&D and experience from military contracts since the early 1960's. The bugs were really worked out before 1960, since the Model 601 was made from 1959-1963, and was known for reliability. The guns have always been reliable, as long as plenty of lubrication is used.
Company after company in the civilian sector have had to re-learn lesson after lesson about what makes the AR reliable, without any help from Colt, and lots of kinks along the way. Correct alloys, heat treatment, technical data packages, assembly procedures, carrier weights, fasteners, spring material and specs, etc. are not just used because they are cool. When you start tweaking with all these aspects of the gun, things stop working, especially when someone makes a "better" or "improved" component.
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LRRPF52 Wrote:Colt has the benefit of years of initial research from Armalite, as well as years of R&D and experience from military contracts since the early 1960's. The bugs were really worked out before 1960, since the Model 601 was made from 1959-1963, and was known for reliability. The guns have always been reliable, as long as plenty of lubrication is used.
Company after company in the civilian sector have had to re-learn lesson after lesson about what makes the AR reliable, without any help from Colt, and lots of kinks along the way. Correct alloys, heat treatment, technical data packages, assembly procedures, carrier weights, fasteners, spring material and specs, etc. are not just used because they are cool. When you start tweaking with all these aspects of the gun, things stop working, especially when someone makes a "better" or "improved" component. AMEN x1000!!! 
Colt has been there and done that for over 50 years. When I see the multitude of gimmicks that roll out in what sometimes seems to be an endless procession I bang my head against the wall. Sometimes somebody finds some small desireable tweak, but most of them turn out to be solutions to nonexistent problems.
Bill Alexander
Unregistered
The Grendel/Beowulf extractor has a slightly different geometry to a 5.56 as the case has a larger rim dimension and allows a more positive engagement. The problem with the extractor jumping the rim is largely removed by the heavier rim so it is not necessary to place the extractor under as much force. This has two benefits, The extractor itself is not flexed as severely so this area of failure is removed and the extractor spring itself can be lighter. Using a lighter spring with less mechanical compression extends the life of the spring. The downside is that the bigger rim demands a larger extractor cut. this can weaken the extractor unless it is reinforced at either side of the extractor flag and this in turn tightens the tolerances between the extractor and the barrel extension during feeding.In instances where the vendor is not in control of the parts or where they are negligent of such consideration a binding condition can occur.
Anyone here able to tell everyone the tolerance stack on the barrel extension minor?
Turning to the extractor pivot pin this cannot fall out of the bolt during use as it is retained within the carrier bore.
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Colt has always been the standard for the stoner system. They have also been the standard for what not to do when it comes to the civilian firearm's market. It seems to be going back to it's civilian roots but only time will tell.I can remember waiting 8 months for any type of part for my sp1 rifle and still have a bad taste in my mouth from those experiences. In ovation or gimmick is determined on the battlefield, shooting competition and the most important one the bank account . That is why we have this forum to hash it out. Colt may have worked the kinks out of there stoner system but there is a tsunami of AR venders who have taken up the slack of colts failures and rightfully so. This is why we need to keep an open mind on any new concept. The military's the one who determines the spec's on the rifles being built not colt. And believe me the military or any other government agency is not the last word on product perfection or cost effectiveness.
@LRRPF52 and Bill -
Thanks for that meaningful insight, you are both spot on. Information that I wish I had armed myself with prior to attempting the BCM extractor upgrade.
Thus far (30 rounds) the DPMS 5.56 replacement spring and insert have not caused a problem with function.
BB
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