Last two uppers that were placed on this lower had ejection issues. First was an SR15 upper that ran well for about 2k, then began to have stovepiping problems that seemed to be remedied by a new ejector spring and the latest upper has been experiencing incomplete ejections. At least once, but sometimes several times per magazine. Empty case remains in receiver and gets locked up when the rifle tries to chamber next round. The manufacturer has agreed to look at it and I’m going to take them up on it, but it had me wondering if something else may be going on. Is there a desired depth for the receiver extension in relation to how far the carrier can travel into it?
I’ve tried 3 separate extensions (BCM, LMT, and a unit from G&R) that when threaded into the reciever just begin to cover the retainer, when threaded another turn, the extension binds on the buffer retainer as well as sitting far enough forward to keep the upper from being able to close on it. I’ve had no issues with the retainer popping loose, but was curious as to whether the extension can allow the carrier to travel too far to the rear and cause cases to be ejected improperly or bounce them off the rear of the port and back into the receiver? When the CH is drawn all of the way to the rear, the face of the bolt appears flush with the ejection port. I’ve read that this may be an issue. Pics below.
Have you replaced the buffer spring with a fresh one? Wear life is generally 3-5k rounds, if I remember correctly. YMMV.
Your first photo shows the correct position for the receiver extension, just catching the lip of the buffer retainer. All three receiver extensions should give you an identical fit, assuming they are manufactured properly. If you are experiencing the same issue with all three, it may be safe to assume that the problem isn’t caused by receiver extension fit.
Pic 2 seems to be the correct way it should be mounted. I can almost guarantee that this has nothing to do with the lower. The fact that the ejectors were replaced really has nothing to do with the rest of the issue.
Daniel Defense 16" CAR gas barrel. DD upper and RIS II with shaved FSB. H buffer was used and ammo used was XM-193 and PMC Bronze.
BCG is factory DD. Gas key is tight, ejector tension seems normal (pulled it and inspected it), extractor is using whatever spring they use and looks to be okay. No O-ring is used.
I’m confident DD will handle it, just wanted to rule out the lower as the last upper on it had ejection problems too.
Pat Rogers has said that his class has experienced ejection issues with DD BCG. in each case, this was fixed with the ejector upgrade kit from BCM which includes a 5 coil spring, little rubber thingie that goes inside the spring and an o-ring though the o-ring was not used.
I have upgraded all my DD bolts with the BCM kit and have not experienced any issues…
Gunz, I have no idea. It does not appear to be a gas issue as the rifle is locking back on empty mags and when it is ejecting properly, the ejection is swift and positive.
ra2bach, thanks for the tip. I was unaware of this, figured I would have seen that posted somewhere, given the popularity of DD rifles and components.
Now that is interesting to me, my DD upper with DD BCG began having extraction problems so I replaced the extractor, spring and insert with the BCM kit. No issues since then, but I just did this a couple weeks ago.
Anyway, that’s news to me so thanks for posting, ra2bach. I thought this was just a ‘one-of’ event so curious if it affects more DDs. Fortunately in this case it seems to be a simple cheap fix. Don’t know about AnimalMother556’s problem.
Colt gold extractor springs on order. I’ll test it out before I bother sending it off if that’s all it may need.
Out of curiosity, is there any issue relating to where the bolt face is in relation to the ejection port when the carrier is in full recoil? There’s actually a thread up on TOS regarding it.
