I did it. Fixed ejector RDB.
- Thread starter TheColtCollector
- Start date
Have any of you seen this video
Ejection issue fixed
Basically he believes that the bolt cycling slowly is partly to blame for the ejection issues. Also something about the ejector causing the ejector spring to become bound. And possibly the 16" barrels have more problems than the shorter options.
So Amphibian, i know you are trying to get yours to run slower in full auto.
I wonder if there is a way to increase speed of the bolt, decreasing carrier mass, multistage/progressive spring allowing a fast extraction/ejection event before slowing down the bolt, etc?
Ejection issue fixed
Basically he believes that the bolt cycling slowly is partly to blame for the ejection issues. Also something about the ejector causing the ejector spring to become bound. And possibly the 16" barrels have more problems than the shorter options.
So Amphibian, i know you are trying to get yours to run slower in full auto.
I wonder if there is a way to increase speed of the bolt, decreasing carrier mass, multistage/progressive spring allowing a fast extraction/ejection event before slowing down the bolt, etc?
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I kmow at one point Amphibian used a nail to try to keep the spring aligned. Why not measure the depth of the ejector hole, insert a stainless nail just long enough so that the ejector can't go any deeper into the bolt than flush. If that makes sense.
I just watched his video.
I tried so many different ejector springs including the Tubb and it will fail too around 1K rounds.
The guy in the video needs to document spring strengths like I did.
Once it gets to 5lbs, it is about to die.
The issue is the headspacing gap kills the spring but as documented on my site, if you don't have the gap it isn't violent enough to kick the brass out with the spring loaded ejector but no problem for a fixed ejector.
That is what I did but the spring still got deformed.
Got fed up and went with my fixed ejector.
I don't regret it as it is way more reliable....till the bolt breaks since the RDB system puts so much stress on the cam pin.
CMMG stated that they use some special material for the cam pin and not to use a standard one as they will break.....I also broke two of the factory CMMG RDB cam pins on my original barrel but I believe it is because that early factory barrel had excessive headspacing as documented on my site.
Too soon to say since it is just out but I don't think the bolts will break since they moved the cam pin hole further back so the ejector slot isn't near it.
I think they could tighten up the headspacing now as well.
I'm not interested in the dissent since it isn't readily full auto capable and I actually want to use the buffer tube since i want to be able to tune it with buffers and springs.
Even if the Dissent were FA capable, I'm sure it would run over 1000 RPM which is not desirable for me either.
How about a spring loaded fixed ejector. The ejector could pop out into the space between the carrier and the bolt lugs as the bolt travels rearword. This way, only the slot and some lead-in into the bolt face would need to be machined.
The spring loaded ejector would just ride along the bolt carrier. If its designed similar to the radian raptor charging handle (no force on the pin) it could be pretty robust.
The spring loaded ejector would just ride along the bolt carrier. If its designed similar to the radian raptor charging handle (no force on the pin) it could be pretty robust.
SecondAmend
Well-known member
- Joined
- Apr 3, 2007
- Messages
- 1,741
The Olympic Arms (OA) AR pattern PCC uppers have/had a spring type ejector mounted in the upper. The ejector rides against the bolt carrier until the BCG is rearward and then the ejector flips inward to engage the rear of the casing and cause the casing to be kicked out the ejection port. In the OA ejection system, the "weak link" is the spring region of the ejector. As has been noted, in the CMMG system, the ejector spring can be that system's "weak link".
In the OA system, the ejector riding on the BCG also had the benefit of providing coulombic damping to the recoil management which contributed to the smooth feel which the OA system was noted for; and the ability to use less than is typical reciprocating mass for recoil management.
MHO, YMMV, etc. Be well.
Remember that the bolt still needs to have some rotation unlike a straight blowback or even a delayed blowback like the MDP9 which uses a spring loaded ejector. The issue is that even if it was spring loaded the ejector still needs to be placed after the cam pin hole so you still need to slot the bolt in that area which weakens the bolt.
In the initial post of this thread and in several others....I saw the words "locking lugs" and "headspace" used in conjunction with RDB. At no time is this action locked so removing one of the lugs is no great loss for a fixed ejector.....and as it isn't locked...headspace isn't really a thing as it describes a point a specific distance from the breech face of the bolt to the chamber shoulder in straight wall cases, or the shoulder in bottle neck cases.....or even the rim on a rimmed round. This lack of a fiex point to "headspace" on is the root of the ejector issues with the action in higher pressure cartridges. the Ejector is pushing the rim out against the extractor when the weapon is fired, allowing the spring to cycle at a rate it isn't capable of. While only a few thousandths per firing cycle.....it is a cumulative effect. RDB is an interesting action for what it is....but do not be lulled into a sense of security about it......at the end of the day it is a blowback with moving parts. Just my humble opinion 
PS Amphibian , not directed at you....I know you understand the physics of RDB as well as I do.....just thought it needed to be said for the less tech savvy
PS Amphibian , not directed at you....I know you understand the physics of RDB as well as I do.....just thought it needed to be said for the less tech savvy
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