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Posted: 6/24/2025 8:07:23 PM EDT
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Just bought my first rifle suppressor; a low backpressure B&T SRBS and put it on my 2013 Knights SR15 with E3 bolt and 3932 total round count on the gun. Suppressor is attached using a Surefire HUB quick-disconnect. The gun has always been on the under-gassed side but runs fine with 4 o'clock ejection on anything EXCEPT super-cheap super-weak reloads which will occasionally short-stroke. I got 2 stovepipes in the first few shots then fired 50 more rounds without incident. I noticed my ejection was at 3 o'cock but VERY weak, spent casing landing about 2 feet from me. I got home and discovered I could comfortably push-down the ejector with my finger. I'm thinking my ejector was already failing and adding the suppressor sped-up the carrier just enough to "catch" the spent casing upon bolt closing. I have replaced the ejector with the JP Enterprises "enhanced" ejector and will be testing it this weekend. The question is though, why the hell did the ejector spring fail after just 4000 rounds?!?! I understand it's a wear item but typically they are replaced at like 10,000 rounds as a preventative measure. I inspected the old ejector after I replaced it and upon casual inspection seemed fine (spring wasn't broken but was discolored towards the middle. Looked like carbon from the little vent hole in the bolt, not rust). Gun was very rarely left loaded, and even then only for a couple days. On a side note, the ejector installation tool available on Brownells made what would be a hellacious install job increadibly easy. Thank you and looking forward to your expertise! |
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Originally Posted By SnowCharger: Just bought my first rifle suppressor; a low backpressure B&T SRBS and put it on my 2013 Knights SR15 with E3 bolt and 3932 total round count on the gun. Suppressor is attached using a Surefire HUB quick-disconnect. The gun has always been on the under-gassed side but runs fine with 4 o'clock ejection on anything EXCEPT super-cheap super-weak reloads which will occasionally short-stroke. I got 2 stovepipes in the first few shots then fired 50 more rounds without incident. I noticed my ejection was at 3 o'cock but VERY weak, spent casing landing about 2 feet from me. I got home and discovered I could comfortably push-down the ejector with my finger. I'm thinking my ejector was already failing and adding the suppressor sped-up the carrier just enough to "catch" the spent casing upon bolt closing. I have replaced the ejector with the JP Enterprises "enhanced" ejector and will be testing it this weekend. The question is though, why the hell did the ejector spring fail after just 4000 rounds?!?! I understand it's a wear item but typically they are replaced at like 10,000 rounds as a preventative measure. I inspected the old ejector after I replaced it and upon casual inspection seemed fine (spring wasn't broken but was discolored towards the middle. Looked like carbon from the little vent hole in the bolt, not rust). Gun was very rarely left loaded, and even then only for a couple days. On a side note, the ejector installation tool available on Brownells made what would be a hellacious install job increadibly easy. Thank you and looking forward to your expertise! |
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One thing that stresses an ejector spring is crud. That tiny space the ejector has to move can let soot and junk in, which in turn causes friction and drag. This keeps the spring from being able to compress and expand properly. An “undergassed” rifle tends to have more soot and crud stay in the upper because there’s less pressure to push it out through the carrier vents. I am one of “those guys” who says that “the ejection chart” is ONLY a diagnostic tool for figuring out where a problem is. And if the rifle ejects consistently - whatever direction - there is no problem. Key point is “consistently”; if Brand B ammo always ejects in pretty much the same direction, that’s just peachy, WHATEVER direction it is. However, if that same Brand B ammo starts ejecting differently, then you have a problem, and the chart can help point you in the right direction. Maybe. Less powerful ammunition tends to give the system less energy to cycle, and the system will cycle more slowly. But if it cycles consistently, all you’re seeing is an artifact of the power level of the ammunition you’re using. All of this does have a bearing on the ejector spring appearing to have failed. (You won’t know if that’s true until you test the rifle with the new spring and the same ammunition.) Use the indications you have when cleaning the upper to determine whether you need to concentrate on the bolt as well. Ejector springs in 5.56 caliber bolts are supposed to be good for at least a few times more rounds than you’ve fired. Yours might fail due to extra crud, due to the spring just being not up to par, or something else. But more than 3k is not super early for it to fail, so I wouldn’t be super concerned about this being “a thing”. |
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Originally Posted By GHPorter: One thing that stresses an ejector spring is crud. That tiny space the ejector has to move can let soot and junk in, which in turn causes friction and drag. This keeps the spring from being able to compress and expand properly. An “undergassed” rifle tends to have more soot and crud stay in the upper because there’s less pressure to push it out through the carrier vents. I am one of “those guys” who says that “the ejection chart” is ONLY a diagnostic tool for figuring out where a problem is. And if the rifle ejects consistently - whatever direction - there is no problem. Key point is “consistently”; if Brand B ammo always ejects in pretty much the same direction, that’s just peachy, WHATEVER direction it is. However, if that same Brand B ammo starts ejecting differently, then you have a problem, and the chart can help point you in the right direction. Maybe. Less powerful ammunition tends to give the system less energy to cycle, and the system will cycle more slowly. But if it cycles consistently, all you’re seeing is an artifact of the power level of the ammunition you’re using. All of this does have a bearing on the ejector spring appearing to have failed. (You won’t know if that’s true until you test the rifle with the new spring and the same ammunition.) Use the indications you have when cleaning the upper to determine whether you need to concentrate on the bolt as well. Ejector springs in 5.56 caliber bolts are supposed to be good for at least a few times more rounds than you’ve fired. Yours might fail due to extra crud, due to the spring just being not up to par, or something else. But more than 3k is not super early for it to fail, so I wouldn’t be super concerned about this being “a thing”. Excellent response; You've given me some things to think about. One thing you made me realize is I used to put a drop of oil on the ejector then push it up and down a few times so the oil will work its way in. However I've found myself not doing so recently. Perhaps I need to resume that practice. You're definitely right about undergassed=dirty... of the 4 or 5 rifles I own/have owned this is definitely the one that gets dirtiest quickest. Another thing that occurred to me is that the hole the ejector is in may be drilled to deep; the new ejector I just installed is several times stronger than the one that failed, but still not as strong as my other rifle I compared it to (a Geissele). The comment about the ejector spring having just not been up to par; that's a definite possibility. This rifle was probably manufactured during the gun panic of 2013. Perhaps the spring wasn't quality-controlled correctly. Thank you for the info; you've given me some good ideas. I think my solution will be to keep an ejector-kit on-hand and just replace it every few thousand whether it has problems or not. Also I'll resume directly lubing the ejector. |
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I forgot to add that your comment about the Brownells bolt tool is spot on. The ARFCOM store used to have a machined Delrin (I think) tool that was even simpler: you put the bolt in it with an empty case stuck on the bolt face, the tool holds the case in place and the case head pushes the ejector in so you can drive the pin out. In true ARFCOM style, I have both the ARFCOM tool and the Brownells tool. 
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Originally Posted By GHPorter: I forgot to add that your comment about the Brownells bolt tool is spot on. The ARFCOM store used to have a machined Delrin (I think) tool that was even simpler: you put the bolt in it with an empty case stuck on the bolt face, the tool holds the case in place and the case head pushes the ejector in so you can drive the pin out. In true ARFCOM style, I have both the ARFCOM tool and the Brownells tool. You're right; the right tool makes all the difference. Tools are almost always a good investment. |
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