Unusual 300blk FTE

[Superhero]

I installed the colt springs specifically to avoid o-rings lol

It locks back on an empty mag every time, no problem.

I'll try my other BCG on it the next time I can make it to the range. Also, waiting on the mail for my ammo order!

Friends don’t let friends O ring. If the extractor spring needs an O ring to function reliably, the spring needs to be replaced.

Superhero, do the simple things first. Try a different BCG as Clint suggested. Do a lockback check to see if it’s under gassed.

The malfunction sounds like a bad extractor spring.

[Superhero]

I have a colt spring installed. Are you recommending reinstalling the standard spring and oring instead?

The extractor has a bounce in the cycle, a difference in timing (like adding a suppressor) can make the difference in it coming back down on the rim or not.

Add extractor tension. O-Ring and standard extractor spring or an extra power extractor spring.

[Superhero]

In slow-mo you can see the bolt bounce. I hadn't considered this might be causing it to slip the rim of the case.

It was in some military, Crane, or Arsenal report. I don’t recall it being specific on the cause, just that failed extraction wasn’t just the extractor slipping over the rim.

It showed that both the M16 and M4 did it but the timing difference made a malfunction much less likely in the M16.

[Todd.K]

I have a colt spring installed. Are you recommending reinstalling the standard spring and oring instead?

Colt gold? They are good in most applications, and have a good lifespan because they aren’t over stressed.

The Colt gold spring may not be too much, but I believe combining an Oring with too much extra power spring is the main reason some have had problems. I choose to run either the gold spring alone or rifle spring + Oring on shorties.

The idea that rubber is inherently unsuitable as a compression spring helper is… narrow minded. What do you think that rubber “buffer” inside your spring is doing? All materials are a compromise with properties in both the plus and minus. In this case there is a very limited space to fit more spring without compromising the stress level and thus lifespan.

[MistWolf]

It’s not that I think the O ring isn’t suitable as a “spring helper”. O rings flatten, dry out, get oil soaked and when they fall apart, the debris will gum up the extractor.

[TMS951]

What should I be looking for in the extractor? What might be wrong with it? I've pulled it apart and looked at it closely. No marks, no burrs, nicely machined. It is identical to the extractor on another good BCG I have.

It not working, but another working.

Had a similar issue with and LMT enhanced bolt. Everything looked good. It was new, I replaced the extractor and springs and was all good after.