View Full Version : Question regarding O-ring over extractor spring?
I have a brand new 10.5 andro upper with a brand new BCM BCG with a H3 buffer. The BCG did not come with the o ring. When shooting the upper for the first time, after about 2 full mags I started having FTE with another round trying to feed. I then put the O ring over the extractor spring and that resolved the issue.
My question,
Its a little worrying, to me, that the reliable operation of this gun relies on a 5 cent O ring. Am I thinking about this the wrong way or what? I am fairly new to the AR platform and any insight into this would be appreciated.
Thank you.
If the 5 cent O ring is what it takes to be reliable, so be it. An O ring is pretty fool proof in the end, doesn't really matter how much it cost if it works. With the harsher extraction/ejection cycle of the shorter guns this part of the fix has been around a long, long time. I suppose the other parts are the buffer, and make sure the gun isn't heavily over-gased. And be sure the O ring isn't some cheesy, done in by oil number. I think the good ones are made of nitrile.
If the 5 cent O ring is what it takes to be reliable, so be it. An O ring is pretty fool proof in the end, doesn't really matter how much it cost if it works. With the harsher extraction/ejection cycle of the shorter guns this part of the fix has been around a long, long time. I suppose the other parts are the buffer, and make sure the gun isn't heavily over-gased. And be sure the O ring isn't some cheesy, done in by oil number. I think the good ones are made of nitrile.
Thanks, its a BCM o ring. Do I also need to run the black plastic insert?
Yes it should have the insert in there already
Yes, use the insert. The O-ring supplements the insert, not the other way around.
In some cases you may not need the o-ring, since you were FTE'ing, you did.
Thanks gents, will insert the black insert as well.
I do have a new BCM 11.5 on the way and am also wondering if I will have to utilize the insert and O-ring as well on the BCM upper. Will it just be a shoot and see situation or should it just run out of the box with a new BCM BCG as well?
Thanks gents, will insert the black insert as well.
I do have a new BCM 11.5 on the way and am also wondering if I will have to utilize the insert and O-ring as well on the BCM upper. Will it just be a shoot and see situation or should it just run out of the box with a new BCM BCG as well?
With a BCM the O ring and insert should be there from the get go. Like the others have said the insert needs to be there. Did the Andro not have the insert? If not, that's poor QC.
With a BCM the O ring and insert should be there from the get go. Like the others have said the insert needs to be there. Did the Andro not have the insert? If not, that's poor QC.
Andro upper came with no BCG, I bought the BCM BCG seperately from AIM and it did not have the insert or O ring included. None of the BCM BCG's I have came with the O ring or insert from BCM with the other 2 BCM uppers I have.
Are O-rings at risk of being ruined because of lube? I have O-rings in all my carbines and always dip the assembled bolt (once clean) into a mason jar of Slip 2000 EWL before putting the weapon back together.
Are O-rings at risk of being ruined because of lube? I have O-rings in all my carbines and always dip the assembled bolt (once clean) into a mason jar of Slip 2000 EWL before putting the weapon back together.
I've had cheapies get kind of melty from oil.
I've had cheapies get kind of melty from oil.
What about the old(er) D-rings? They are blue. Have a few of those too.
I have a brand new 10.5 andro upper with a brand new BCM BCG with a H3 buffer. The BCG did not come with the o ring. When shooting the upper for the first time, after about 2 full mags I started having FTE with another round trying to feed. I then put the O ring over the extractor spring and that resolved the issue.
My question,
Its a little worrying, to me, that the reliable operation of this gun relies on a 5 cent O ring. Am I thinking about this the wrong way or what? I am fairly new to the AR platform and any insight into this would be appreciated.
Thank you.
Order a Colt M4 extractor spring. It's the right spring and comes with the right insert. When it comes in, throw away the spring that came with the upper along with the O ring. The O ring was just an interim fix, only to be used until Colt could redesign the extractor spring. Using an O ring with the proper extractor spring places too much tension on the extractor.
Chemicals will destroy O rings not made of the right materials.
Order a Colt M4 extractor spring. It's the right spring and comes with the right insert. When it comes in, throw away the spring that came with the upper along with the O ring. The O ring was just an interim fix, only to be used until Colt could redesign the extractor spring. Using an O ring with the proper extractor spring places too much tension on the extractor.
Chemicals will destroy O rings not made of the right materials.
So BCM O rings are junk? Thats what I put in the BCM BCG thats in the upper.
So BCM O rings are junk? Thats what I put in the BCM BCG thats in the upper.
They are unnecessary and can cause more problems than they fix. If used with the spring that's supposed to be used, there is too much tension on the extractor. If used to beef up a weak spring, they will deteriorate over time and come apart. The pieces will gum up the works and cause extraction issues.
If an extractor spring needs an O ring, the spring is out of allowable limits and needs to be replaced.
An O-ring made of the correct material (No, not the one they have at the local hardware store) is impervious to oil, doesn't break down, and has a longer service life than extra power springs.
I run a standard spring and O-ring on all my bolts.
So BCM O rings are junk? Thats what I put in the BCM BCG thats in the upper.
They used to ship the BCG with the o-ring in a little plastic bag. But do what MistWolf said and get that copper colored Colt spring. It fixed that same issue for me. Different BCG but same issue.
Colt Spring no O-ring.
If the o-rings are rubber yes oil will erode them. That's an unusual application for an o-ring anyway. That spring will be the best $4 you ever spent on an AR.
That would be incorrect, and I would recommend you take a close second look. An extractor spring buffer or insert should be there. If not, you should be contacting BCM.
The O-ring is a band-aid and I would be looking at an upgrading the spring.
Andro upper came with no BCG, I bought the BCM BCG seperately from AIM and it did not have the insert or O ring included. None of the BCM BCG's I have came with the O ring or insert from BCM with the other 2 BCM uppers I have.
Sprinco 5-coil and worry no longer about the o-ring.
If buying a hardware store o-ring, be sure it's Viton with a durometer of 70. I've had good luck with these (heat and solvent resistant). I think some lubes and solvents can eat Buna after awhile. Maybe Todd can correct me on this.
The blue D-fender is resistant to most lubes and solvents. These impart stronger pressure than a standard o-ring, so check your brass rims for damage if you like to reload.
FWIW, when I first got my factory complete BCM 11.5 KMR upper with BCG (BCM Lower, H2 buffer, brand new BCM GI mags & AE XM193 5.56)) I had 4 FTE durning my first trip to the range (300 rounds). The bolt did not come with the O ring installed. I emailed BCM with a detailed description of the issue and my set up. This was their response:
Hi Chris,
Thank you for contacting us and for the very details synopsis. First, you should definitely be running an O ring on your 11.5 upper group. Second, please ensure your magazines are in good working order. Magazine issues can cause malfunctions like this, as can lower powered ammunition like the American Eagle. The H2 buffer is just fine in your upper, however the lack of an O ring coupled with possible bad magazines or ammunition will cause consistent problems.
Please keep us updated.
Bravo Company USA, Inc
I installed the O Ring and haven’t had a single malfunction since.
BufordTJustice
11-05-17, 11:40
They are unnecessary and can cause more problems than they fix. If used with the spring that's supposed to be used, there is too much tension on the extractor. If used to beef up a weak spring, they will deteriorate over time and come apart. The pieces will gum up the works and cause extraction issues.
If an extractor spring needs an O ring, the spring is out of allowable limits and needs to be replaced.
Exactly.
I also rec and use SprinCo 5 coil extractor springs with a std insert. That or the Colt copper spring and you’re GTG.
However, if the original spring was an actual BCM spring, there is another issue with your system. I’ve seen a std LMT (rifle) spring used with only a std insert (no o-ring) on an LMT 10.5” run like a sewing machine with an H3 buffer.
Something else is up.
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Im not sure what is going on here. All BCM bolts and BCGs that I've seen, and I've seen a pile of em, have come with the black insert installed. I would be concerned that someone had fiddled with my BCM bolt - i.e., tampered with extractor spring and insert- if i received a BCM bolt without a black insert installed. I agree with others, assuming the upper is constructed and gassed properly, a quality extractor spring and insert should be adequate for proper extraction.
It is concerning that none of my BCM bcg bought from BCM directly and other vendors does not have the O rings. I do have several of the BCM extractor spring upgrade kits. Are the springs in these kits the same springs that come with the BCM bolts or are they different? I plan to just install those and be done with it.
It is concerning that none of my BCM bcg bought from BCM directly and other vendors does not have the O rings. I do have several of the BCM extractor spring upgrade kits. Are the springs in these kits the same springs that come with the BCM bolts or are they different? I plan to just install those and be done with it.
I think it's come to the point where you need to interact with BCM directly. Really only they can answer these questions to your satisfaction. I would say that it would be very strange that they would have two sets of differing parts....one for individual kits and then one set for more complete sub-assemblies or complete uppers and rifles. As you can see the O ring issue isn't without a some controversy.
It does seem to be controversial. I will reach out to BCM and and hopefully they can clarify and or resolve issue.
Thanks for all input gentlemen. Definitely a learning experience.
I own two BCM BCG's, both purchased directly from BCM. The first one was purchased seperatly and inside the plastic bag it came in, was an o-ring sealed by itself. Luckily I saw it because I would have thrown the bag away. Although I haven't installed it, the upper runs fine.
The second BCG was included free with the upper a couple years back when they were giving them away, it shipped inside the upper and did not have an o-ring installed.
I haven't given it much thought since both of them run like a clock. I thought I read somewhere the o-ring is not needed unless you have extraction issues.
Interestingly both my cheap Toolcraft BCG's, one parkerized from Cryptic Coatings and one black nitride from Monmouth Reloading shipped with o-ring's installed
Viton is the correct material.
It has become a thing to "bandaid" name call the O-ring.
First, rubber can be an engineered spring design.
Second, I have not heard how these extra power springs are able to have an acceptable stress rating, because I have been told they don't. Service life goes down quickly if a spring design is over that, while the O-ring has an almost unlimited service life up to 400 deg. A poorly engineered spring is as worthy of "bandaid" as the O-ring. More tension is needed, but unless you redesign the bolt and extractor you are left with these two options.
Every type o-ring you could possibly ever want and the various chemicals they can and can not withstand.
Not sure what sorts of chemical reactions occur when shooting beyond the greases and oils, but a simple spring probably would not have an issue with any of it.
http://www.theoringstore.com/index.php?main_page=page_3&zenid=9cd9abdb82b22c7f50bdfb7f484e5064
stevenravenscroft
11-05-17, 20:32
My complete 9 inch BCM 300 BLACKOUT upper came without the O ring not installed. 500 rounds to date and no issues. Half of those were with a carbine buffer and the other with a H buffer.
jackblack73
11-05-17, 21:10
My complete 9 inch BCM 300 BLACKOUT upper came without the O ring not installed. 500 rounds to date and no issues. Half of those were with a carbine buffer and the other with a H buffer.
My 9" BCM 300blk came with o-ring installed too. A 16" and 11.5" BCM, both 5.56, did not have the o-ring installed. All run perfectly, although I don't have many rounds through the 300blk.
i was not talking about the O ring. The OP mentioned that some of his BCM bolts did NOT come with the black insert. That is what caused my ears to perk up. I have seen several BCM bolts and BCGs that do not come with O rings. However, of the many BCM BCGs I've seen, I've never once seen a bolt ship without the black insert under the extractor spring. OP, you wanna check your bolts and verify that the black inserts did NOT come with the bolts?
I second the suggestion to contact BCM.
crosseyedshooter
11-06-17, 13:28
This thread is full of conflicting information. I’ve purchased four BCM BCGs with and without 5.56 uppers/rifles in the past three years. They all came with the black insert installed and the o-ring was included in a separate bag.
Definitely let us know what BCM says. I have had several of their uppers and BCGs over the years but I’ve never really paid attention to what was on the bolt. I always assumed that the o-ring in the sealed bag was an extra. Since I’ve never had an issue, I never gave it a second thought.
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Per BCM,
The 16" uppers require no crane O ring so I would have not received them in uppers bought directly from them. 12.5 uppers and below will come with the crane O ring from BCM.
BCM BCG purchased from other vendors will come with O ring in the polytube packaging.
OP,
I know you don't want to hear this, but you need to dump you entire setup and get something factory (LMT, KAC, Colt, DD, Noveske) instead of a cobbled together upper from parts of various brands.
You having extraction issues straight out of the gate tells me your barrel chamber is out of spec.
The black crane o-ring was made to be installed in Colt rifles using a silver extractor spring and either a blue or black insert. This was for the era of Colt rifles from the late 1980s to the early 2000s. If you have anything else than that, you cannot be assured the o-ring will fix any problem due to various extractor springs used by different companies.
If you have a modern Colt gold spring with black insert, you do not need this o-ring.
I don't know if I would use your term "cobbled together", however I am ordering a BCM 11.5 and have a brand new BCM BCG to go in it. The 10.5 andro upper I have now seems to be a good piece of equipment. What will be the reasoning if this new BCM 11.5 requires the O ring? According to your assessment will it be out of spec also?
Cobbled together meaning not a factory assembled and tested complete upper. Don't take it personally.
Cobbled together meaning not a factory assembled and tested complete upper. Don't take it personally.
No taking personally at all.
If you want a 10.5" set up, then I would get a DD 10.3" MK18 upper that has a military dimension gas port size (Make sure you get the mil gas port size, they make two sizes).
This has a more robust rail mounting method and a pinned gas block.
If you want a 10.5" set up, then I would get a DD 10.3" MK18 upper that has a military dimension gas port size (Make sure you get the mil gas port size, they make two sizes).
This has a more robust rail mounting method and a pinned gas block.
Thanks, I am just going to go with a 11.5. The MK18 is a rabbit hole I do not want to go down. I do not have the $$ to do that like my OCD would dictate.
There seems to be a lot of benefit to that extra inch, I’d go with an 11.5 too.
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