who here uses them and who doesnt? I have heard pros and cons to both sides.
I assume you’re referring to o-rings around the takedown lugs to reduce play between the the upper and lower receivers?
In that case, I suggest you read this thread: http://m4carbine.net/showthread.php?t=32599&highlight=accuwedge
It’s primarily about the accuwedge, but o-rings are discussed as well.
My advice: It’s a cheap solution to a non-existent problem that has the possibility of disabling your rifle. Stay away.
Im sorry, I meant extractor orings :D.
D’OH!!!
My M&P came with a black one installed. I don’t plan on making any changes.
My S&W MP15A don’t have them but my S&W MP15T has them. Both rifles run and shoots the same ammo just fine.
I’ve used them in my SBRs for years but my carbines and mid-length I’m running without them. So far I haven’t noticed any performance issues. I am rapidly deciding that they are unnecessary if you have a quality extractor spring. My next carbine class I plan on running my work SBR without out one and I doubt I’ll have any issues.
The more I read, the more I believe carbines dont need them. My BCM bolt has one, but I think I might take it off. Maybe the extractor will last longer that way. Do colt 6920s come with o-rings?
I don’t think it will help or hurt with the life of the extractor but I’m seeing more and more that they are not necessary, but I’m still testing for my uses.
The 6920 I purchased several years ago did not come with one but did have the black insert and a stiff 5 coil spring. I’m not sure what Colt is shipping with these days. I’ve only kept the 6920 for personal reasons since it got me through the academy and it’s the only Pony I own.
Just like condoms O-rings have their time and place. I believe that those who run full-auto or have SBR’s will benefit from them. My belief is that they will actually reduce wear on the extractor spring assy.
Good point. I don’t run FA but I still have the O-rings in my SBRs. Hopefully I’ll get to see how much better or worse they will run without them in this rifle school. I’m expecting to send about 1000-1500 rds downrange over three days. I’ll let you know if mine chokes or if I see any extra wear-and-tear. This will be on a LMT 10.5 with a LMT FA BCG with the BravoCo upgrade without the O-ring.
I’m President of the Anti 0-ring society. I use them on none of my guns… including my SBRs, and I haven’t had a single water leak yet.
Just a little info I witnessed a Wolf ply stuck in a bushy chamber. The extractor ripped the rim off the stuck case. The Bolt was using a blue insert and no O ring.
The Crane O-Rings were orig. designed for the MK18 (10.5).
IMHO, that is really the best place for them. Can you put them in a 16" carbine and have the gun run well? Sure Can. Can you put them in a 16" middy and have it cause a malfunction? Yes you can.
I personally run them in my suppressed 10.5, but do not run them in any other weapon (YMMV).
C4
I guess the consensus is that carbines generally dont need them. I will take mine out and see how she does with just the BCM black insert and spring. I dont really expect it to have problems. Thanks for the replies
Bushies don’t have true 5.56 chambers so I am not surprised. I use the O-rings here on our 14.5 FA carbines and we have no issues. But, I also have been reaming the chambers as well. The reaming wasdue to issues with the east bloc SS109 ammo we were using. With true M855 we had no problems at all.
You mean many Bushies.
Mine is spec, and I believe even Grant would verify that many of the newer ones are true spec. But, not all apparently.
Just clarifying. 
How does one find out if the chamber dimensions are truly in spec?
Safety,
Quite possibly true. I haven’t played with any newer ones. All of ours are about 5 years old. Maybe they did finally get a clue.
I bet the east block stuff was using a faster burning powder with a sharper pressure spike in the tighter throated chambers.
Heavy,
Interesting analysis. We debated the malfunctions and were looking at the ammo being the culprit. Not that it was bade per se, just that it was conflicting with the operating system. With the 5.56 AK’s we have there were no issues at all.