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Posted: 9/23/2014 9:55:46 PM EDT
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11.5" barrel
AAC M4-2000 suppressor AE 5.56 fmj After I built this I was getting FTF. The next round woundnt load into chamber all the way so I got a upgraded piano wire buffer spring and a H3 buffer. This has worked well for over + 1000 rounds with no problems at all. At the range this last weekend, had the boys shooting and they went threw 2 Mags pretty fast. On the third mag I noticed it shot a burst. I fired a couple of rounds and it did it again. The can was of course supper hot so I wasn't sure if it was stove pipping or not. After thinking about it was wondering if the AR was just getting worn in and the combination of the heavy spring and H 3 buffer wasn't letting the bolt travel back far enough to engage the disconector letting the hammer fallow the bolt forward. Today I cleaned and put a STD buffer back in. Hope this works. Does it sound like I'm on the right track or should I be looking at something else? |
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If the bolt carrier is traveling back enough to eject, it's traveling enough to engage the disconnector with the hammer.
My guess is that the heavy spring might be causing some slamfires. The other possibility is that the disconnector/spring has started wearing out. |
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Ditto, disco is out off tune, or the disco spring is worn and causing problems.
Shotgun the upper open, then cock the hammer back until the back hammer sear and the disco sear tips are as close to each other as you can get them with the trigger untouched. Note, if you have not cleaned the FCG in some time (since you are running a can), pull the FCG to give it a good cleaning inside and out. When you reinstall the FCG, make sure to CLP lube the parts, including the pins. The free gap (distance that the hammer back sear can pass by the disco) between the disco and back hammer sear should be in the .001 to .003 range (human hair) with the trigger untouched, and if you find that the free gap is greater than this, then the disco needs to be re-timed. To re-time the disco to get the ideal free gap, you are going to remove metal from the front/bottom of the disco, where it seats against the front/top of the hammer. Hence, by slightly removing metal from the front/bottom of the disco where it seats against the front/top of the trigger, it will allow the disco to cam more forward at rest on the trigger pin/where to seats against the front of the hammer, which in turns decreases the free gap and allows the disco to retain the hammer greater with the trigger held back, and also longer as you release the trigger so the hammer is not bounced on the disco as the carrier closes (jolts). |
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Ditto, disco is out off tune, or the disco spring is worn and causing problems. Shotgun the upper open, then cock the hammer back until the back hammer sear and the disco sear tips are as close to each other as you can get them with the trigger untouched. Note, if you have not cleaned the FCG in some time (since you are running a can), pull the FCG to give it a good cleaning inside and out. When you reinstall the FCG, make sure to CLP lube the parts, including the pins. The free gap (distance that the hammer back sear can pass by the disco) between the disco and back hammer sear should be in the .001 to .003 range (human hair) with the trigger untouched, and if you find that the free gap is greater than this, then the disco needs to be re-timed. To re-time the disco to get the ideal free gap, you are going to remove metal from the front/bottom of the disco, where it seats against the front/top of the hammer. Hence, by slightly removing metal from the front/bottom of the disco where it seats against the front/top of the trigger, it will allow the disco to cam more forward at rest on the trigger pin/where to seats against the front of the hammer, which in turns decreases the free gap and allows the disco to retain the hammer greater with the trigger held back, and also longer as you release the trigger so the hammer is not bounced on the disco as the carrier closes (jolts). i have been having my 15 yr old son clean this weapon last couple of times but ive checked it after words and it looked GTG. I have some extra disconnectors, I will replace it along with a standard buffer spring. reg functon check and cyclig of weapon seems fine. Not sure .000 of gaps. Dont have proper equipment. Thanks for the help. Seems your keeping me on the right track. Thank you. |
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As I said, the free gap distance between the disco sear edge to edge of hammer back sear as you cock the hammer back to get the two as close to each other with the trigger untouched, should be around the distance of a human hair/ two sheet of copy paper.
Hence, you want the edge of the hammer rear sear to almost kiss the the edge of the disco sear as the hammer is being cocked past the disco. This allows for the best retainer of the hammer by the disco with the trigger pulled back, and at the same time, makes the release of the hammer from the disco just before the trigger comes back forward to rest; which prevents operator trigger doubling by accident. |
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As I said, the free gap distance between the disco sear edge to edge of hammer back sear as you cock the hammer back to get the two as close to each other with the trigger untouched, should be around the distance of a human hair/ two sheet of copy paper. Hence, you want the edge of the hammer rear sear to almost kiss the the edge of the disco sear as the hammer is being cocked past the disco. This allows for the best retainer of the hammer by the disco with the trigger pulled back, and at the same time, makes the release of the hammer from the disco just before the trigger comes back forward to rest; which prevents operator trigger doubling by accident. I see what you mean. It seems that I have at least 1/16 to 1/8 gap between the 2. I have another lower with a geiussle 2 stg trigger (I know that's not spelled right. ) It seems to almost touch, if not so a little. I will install another FCG. Do you think the heavy buffer spring had anything to do with faster wear? |
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You probably shouldn't take this to the range. It's now considered a MG. I would think its gotta be a disco/FCG issue but I don't have any suppressor experience. Maybe Dano can help you out tho Lol, I don't think of it as a MG, just a malfunction. Me being a law bidding citizen if I had I'll intent, I wouldn't post this on the Internet. Although we stopped firing it ASAP as soon as the malfunction arose. It does look like a disco prob. |
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New FCG may solve the problem (as long as the problem is not in the lower receiver pin channel locations), but since re-timing a disco is so easy/quick (I have a jig that I can use in the mill to make short work of this), its kind of like throwing the baby out with the bathwater trashing a FCG that the disco just needs to be correctly timed instead.
About the only time I throw my hands up on a FCG, is when the trigger front edge from pin channel has been milled too short to begin with, since this cause the hammer to be retained too high by the trigger (think colt L cut hammers with un-shrouded carriers and the hammer catching the FP stop collar), and not matter how much more you mill off the front of the trigger to try to resolve the problem, its still going to be too short. 
(whole joke of cutting a piece of lumber a second time, and it's still too short). |
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Very interesting. Please correct me if I have this wrong
1) dbl00buck does not have a worn out fire control group. The H3 buffer and stout spring have nothing to do wear and tear wise w/ the FCG. 2) This issue took 1000 rounds to show itself? 3) His issue is an out of spec lower? Could this issue arise from the '.50 trigger job' or Bill Springfield's work? edit for spelling |
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Very interesting. Please correct me if I have this wrong 1) dbl00buck do not have a worn out fire control group. The H3 buffer and stout spring have nothing to do wear and tear wise w/ the FCG. 2) This issue took 1000 rounds to show itself? 3) His issue is an out of spec lower? Could this issue arise from the '.50 trigger job' or Bill Springfield's work? Didn't think about that. If you have any work done by Bill Springfield done on this FCG, melt it down to a fiery death before it kills somebody lol |
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Very interesting. Please correct me if I have this wrong 1) dbl00buck does not have a worn out fire control group. The H3 buffer and stout spring have nothing to do wear and tear wise w/ the FCG. 2) This issue took 1000 rounds to show itself? 3) His issue is an out of spec lower? Could this issue arise from the '.50 trigger job' or Bill Springfield's work? edit for spelling $.50 trigger job does not say to remove metal from the sears, only to polish the surfaces. Custom Trigger job, before you do anything else, you make dam sure that the disco is set correctly from the start, and if you are removing trigger or hammer metal, then these parts need to be re-hardened. As for the disco timing (free gap) growing through live fire, yes. Its the parts/pins/ receiver pin channels mating in against each other, but will back up to state that the disco timing should have been checked from the start (within the .001" to .003") and as the parts do mate in to case a increase in disco free gap, it still leaves the gap still small enough to work correctly. To sum it up, the rifle started with a large Disco free gap that allowed the question gap to work with the parts still tight, and as the FCG parts mated in, this increase in disco free gap is what is causing the problem now. So instead of the disco having an ideal free gap of .001" to .003", the rifle now has a free gap in the .100"+ range instead (started off way to big to begin with, and just got worse as the parted matted in). As for if this FCG was custom smith'd, then someone needs to raise royal hell with the smith that got paid to do this trigger job; since as stated, disco free gap is the first thing that needs to be checked/resolved before you do anything else to the FCG. |
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$.50 trigger job does not say to remove metal from the sears, only to polish the surfaces. Custom Trigger job, before you do anything else, you make dam sure that the disco is set correctly from the start, and if you are removing trigger or hammer metal, then these parts need to be re-hardened. As for the disco timing (free gap) growing through live fire, yes. Its the parts/pins/ receiver pin channels mating in against each other, but will back up to state that the disco timing should have been checked from the start (within the .001" to .003") and as the parts do mate in to case a increase in disco free gap, it still leaves the gap still small enough to work correctly. To sum it up, the rifle started with a large Disco free gap that allowed the question gap to work with the parts still tight, and as the FCG parts mated in, this increase in disco free gap is what is causing the problem now. Quoted:
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Very interesting. Please correct me if I have this wrong 1) dbl00buck does not have a worn out fire control group. The H3 buffer and stout spring have nothing to do wear and tear wise w/ the FCG. 2) This issue took 1000 rounds to show itself? 3) His issue is an out of spec lower? Could this issue arise from the '.50 trigger job' or Bill Springfield's work? edit for spelling $.50 trigger job does not say to remove metal from the sears, only to polish the surfaces. Custom Trigger job, before you do anything else, you make dam sure that the disco is set correctly from the start, and if you are removing trigger or hammer metal, then these parts need to be re-hardened. As for the disco timing (free gap) growing through live fire, yes. Its the parts/pins/ receiver pin channels mating in against each other, but will back up to state that the disco timing should have been checked from the start (within the .001" to .003") and as the parts do mate in to case a increase in disco free gap, it still leaves the gap still small enough to work correctly. To sum it up, the rifle started with a large Disco free gap that allowed the question gap to work with the parts still tight, and as the FCG parts mated in, this increase in disco free gap is what is causing the problem now. Thanks Dano523. I guess I would expect any issues to show themselves immediately, but that is the wrong premise. So, Is this a situation of parts wearing in and tolerance stacking? 1) FCG wear surfaces, pins and receiver holes reach a point where something exceeds the design 2) Receiver is within spec as to pocket milled, holes drilled, right dimensions. Poly? 3) The parts, as they broke in, exceeded the design tolerances. |
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Over thinking it,
Disco not machined timed to spec, which causes the disco Free gap too be to large to begin with (read as you are assembling the lower, do not trust that is plug and play, and disco free gap needs to be check and if needed, re-timed then). As the pins mate to the trigger and hammer pin channels, and the pins mate to to the receiver channels, you get a few thousands of growth/slop, which transfers back to the Free gap of the disco now being even larger that the original gap that was too large to being with. Also throw in that as the upper receiver surfaces starts to self polish out to the carrier, the carrier is now moving faster once mated in, which cause even more of a impact jolt as the bolt locks home with a live round that the disco has to still retain the hammer against this closing jolt when you have the trigger pulled back. As for checking free gap on a rifle, you don't even need to open the action to check it. Just make sure that the rifle is unloaded, hold the trigger back, pull the charging handle back and release the charging handle to cock the hammer on the disco then lock the bolt home, then slowly release the trigger. The hammer should not be released from the disco until the trigger is around 1/8" or less from it's front at home rest position. With the release/free gap set to this (.001" to .003"), it allows the disco sear to cam as far as possible into engagement with the hammer back sear when the trigger is help back, and at the same time, prevents finger trigger bounce during firing to cause the rifle to operator bump fire it by accident. |
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Didn't think about that. If you have any work done by Bill Springfield done on this FCG, melt it down to a fiery death before it kills somebody lol Quoted:
Quoted:
Very interesting. Please correct me if I have this wrong 1) dbl00buck do not have a worn out fire control group. The H3 buffer and stout spring have nothing to do wear and tear wise w/ the FCG. 2) This issue took 1000 rounds to show itself? 3) His issue is an out of spec lower? Could this issue arise from the '.50 trigger job' or Bill Springfield's work? Didn't think about that. If you have any work done by Bill Springfield done on this FCG, melt it down to a fiery death before it kills somebody lol Just a STD FCG. No trigger work done at all. |
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Photo again please, but this time, do not touch the trigger, and get the disco sear and the back hammer sear edges as close to each other as possible when you take the picture (hammer need to lowered down around another 1/8" so the two sear edges are as close to each other as you can get them).
Again, the free gap is the distance between the two sear edges that will allow the hammer sear edge to pass past the disco sear edge without the disco catching the hammer when the trigger is untouched/all the way forward at is normal rest position. |
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Photo again please, but this time, do not touch the trigger, and get the disco sear and the back hammer sear edges as close to each other as possible when you take the picture (hammer need to lowered down around another 1/8" so the two sear edges are as close to each other as you can get them). Again, the free gap is the distance between the two sear edges that will allow the hammer sear edge to pass past the disco sear edge without the disco catching the hammer when the trigger is untouched/all the way forward at is normal rest position. Hope this video helps a little more. I must be confused of what you needed to see. I also notice that the heavier buffer spring was 8 coils longer than my other 2 springs. Can this cause any issues? |
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Hope this video helps a little more. I must be confused of what you needed to see. <a href="http://i1258.photobucket.com/albums/ii524/Dbl00buck/IMG_4558_zps824efd69.mp4" target="_blank">http://i1258.photobucket.com/albums/ii524/Dbl00buck/th_IMG_4558_zps824efd69.mp4</a> I also notice that the heavier buffer spring was 8 coils longer than my other 2 springs. Can this cause any issues? Quoted:
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Photo again please, but this time, do not touch the trigger, and get the disco sear and the back hammer sear edges as close to each other as possible when you take the picture (hammer need to lowered down around another 1/8" so the two sear edges are as close to each other as you can get them). Again, the free gap is the distance between the two sear edges that will allow the hammer sear edge to pass past the disco sear edge without the disco catching the hammer when the trigger is untouched/all the way forward at is normal rest position. Hope this video helps a little more. I must be confused of what you needed to see. <a href="http://i1258.photobucket.com/albums/ii524/Dbl00buck/IMG_4558_zps824efd69.mp4" target="_blank">http://i1258.photobucket.com/albums/ii524/Dbl00buck/th_IMG_4558_zps824efd69.mp4</a> I also notice that the heavier buffer spring was 8 coils longer than my other 2 springs. Can this cause any issues? Dano can tell you for sure, but IIRC the rifle action springs are longer than carbine springs and can cause problems when mismatched. ETA- the more I think about this the more I think this spring could be the problem. If you still have the standard carbine buffer spring go see what that does. Itll prob work! |
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Dano can tell you for sure, but IIRC the rifle action springs are longer than carbine springs and can cause problems when mismatched. ETA- the more I think about this the more I think this spring could be the problem. If you still have the standard carbine buffer spring go see what that does. Itll prob work! Quoted:
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Photo again please, but this time, do not touch the trigger, and get the disco sear and the back hammer sear edges as close to each other as possible when you take the picture (hammer need to lowered down around another 1/8" so the two sear edges are as close to each other as you can get them). Again, the free gap is the distance between the two sear edges that will allow the hammer sear edge to pass past the disco sear edge without the disco catching the hammer when the trigger is untouched/all the way forward at is normal rest position. Hope this video helps a little more. I must be confused of what you needed to see. <a href="http://i1258.photobucket.com/albums/ii524/Dbl00buck/IMG_4558_zps824efd69.mp4" target="_blank">http://i1258.photobucket.com/albums/ii524/Dbl00buck/th_IMG_4558_zps824efd69.mp4</a> I also notice that the heavier buffer spring was 8 coils longer than my other 2 springs. Can this cause any issues? Dano can tell you for sure, but IIRC the rifle action springs are longer than carbine springs and can cause problems when mismatched. ETA- the more I think about this the more I think this spring could be the problem. If you still have the standard carbine buffer spring go see what that does. Itll prob work! Out of the several piano wire buffer springs I've seen and some I've used, they were all longer than a standard spring. Never an issue though. |
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dbl00buck, your free gap is on the .020" range, and the disco still needs to be timed with the new FCG.
So on that note, put the old FCG back in the rifle, and lets time that one correctly instead. Your good on the video, but once you cock the hammer back, do not touch the trigger. With the hammer cocked back for the trigger to retain the hammer, now over cock the hammer a few time and let it back up for the trigger to catch the hammer again. When you are doing this, look at the distance that the back hammer sear edge clears the discos sear edge on the over cocks. What we want is for the two to clear each other by about a human hair. So pull the hammer, then drift the trigger pin out enough that you can pull the disco. With the disco in hand, you want to remove metal from the front bottom surface of the disco where it seats against the top front of the trigger, so when you reinstall the disco back into the trigger via the trigger pin, the disco sear is angled more forward in the trigger (this closes the free gap). Helps to vise the disco up so you can draw file the bottom of the disco to keep that surface straight, and do a few light passes to remove metal off the bottom of the disco with a few dry fittings alone the way to test the timing. Also to note, if you slightly over do it with metal removal on the disco and the two sears lightly kiss as you are over cocking the hammer, your still fine (just need to make a file pass on the edge of the disco sear to gain back some free gap). This bottom edge is where you are filing, 
And here is the relationship of the trigger to disco that determines the free gap timing (read do not file on the front of the trigger, just the bottom of the disco only. 
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Pick a strain of hair off your head , hold it between the hammer back sear edge and the disco sear edge, then when you over cock the hammer down below the disco sear, I want the sears to snap both sides of hair as they pass by each other, or even cut the hair (read have a touch more filing to do since a hair is around .004 and we want less than a gap that that between the two)..
Also, before you file the disco again, take a sharpie marker and marker smoke the bottom edge of where you are filling the disco, put the disco back in the trigger with the pin, move the disc side to side, then pull the disco back out to look at where the sharpy marker smoking has been rubbed off. This rubbed off markerless areas are where you want to focus on filing, since they are the high spots that are making the contact to the top of the trigger. |
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Pick a strain of hair off your head , hold it between the hammer back sear edge and the disco sear edge, then when you over cock the hammer down below the disco sear, I want the sears to snap both sides of hair as they pass by each other, or even cut the hair (read have a touch more filing to do since a hair is around .004 and we want less than a gap that that between the two).. Also, before you file the disco again, take a sharpie marker and marker smoke the bottom edge of where you are filling the disco, put the disco back in the trigger with the pin, move the disc side to side, then pull the disco back out to look at where the sharpy marker smoking has been rubbed off. This rubbed off markerless areas are where you want to focus on filing, since they are the high spots that are making the contact to the top of the trigger. Ok, sorry it took me so long got busy with life. I filled it down enough where it cuts a hair and it touches just a hair ( pun intended ). No doubt taking this trigger apart so many times I feel like I can do it in my sleep. I did notice that I had the disco spring installed upside down not leattin the disco travel all the way like it's suppose to. Even tho it makes me look stupid, I wanted to share this tid bit just in case it mattered. Hopefully this issue is resolved and I will keep this information and pass it along if the need ever rises. Thank you so much for the insight and time you have given me. I will for sure unfuck myself ol great one. If there is anymore I need to do, I will be waiting. Again, thank you.... |
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