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Posted: 5/30/2011 6:36:15 PM EDT
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I had posted a couple of weeks ago about an extraction problem I've been having. I followed what everyone had suggested and I (finally) went shooting today, but I'm still getting casings stuck in the upper.
Things I've done:
I thoroughly cleaned it before I went shooting so I'm pretty sure it's not a build up of carbon. I'm a civilian that works for the National Guard, so I took my bolt+carrier into the armorer and he said that the pressure on the extractor claw and the extractor spring were good. I have a laser bullet (a laser pointer in the shape of a .223 round, used to setup my sights) that if I chamber, and then pull back on the charging handle really quickly, I can get the laser bullet to fling a good 2-3 feet, where as when I was shooting my bullets ( .223 62 grain Green Tip. Lake City brand) they were falling 4-6 inches from the rifle, or get caught between the bolt and the upper. what else could I do to trouble shoot this problem? Thanks! |
| I've tried it with 3 types of ammo, and all three do the same thing. Cases land 4-6 inches from rifle (laying prone). Factory reload 55 grain Rem, new 62 grain Lake City, and factory reload PMC 55 grain. I also think I ran a clip of 20 rnds of Wolf (that's what happens when you let your buddies by the ammo) and I'm pretty sure they jammed as well. |
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What else could cause the short stroke problem other than gas issues? I checked for leaks in the tube and the carrier key with an air compressor (~ 75 psi) and some bubble solution around the creases and no bubbles formed. Is there another test I can do to check for gas problems?
What about my spring? I checked the length and it was correct. I also checked the buffer length and it was correct. Maybe the buffer weight is incorrect? What is the correct weight for the M4 carbine model AR-15 buffer? Thank you for your help! I really appreciate it. |
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Quoted: What else could cause the short stroke problem other than gas issues? I checked for leaks in the tube and the carrier key with an air compressor (~ 75 psi) and some bubble solution around the creases and no bubbles formed. Is there another test I can do to check for gas problems? What about my spring? I checked the length and it was correct. I also checked the buffer length and it was correct. Maybe the buffer weight is incorrect? What is the correct weight for the M4 carbine model AR-15 buffer? Thank you for your help! I really appreciate it. For carbine length gas systems, I tell people to start with the H buffer, as a minimum, with H2 for M193/M855 ammo. Some carbines need the H2 for both .223 and 5.56. Did you pull your FSB and check it for alignment with the gas port and the diameter of your gas port? |
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Quoted:
For carbine length gas systems, I tell people to start with the H buffer, as a minimum, with H2 for M193/M855 ammo. Some carbines need the H2 for both .223 and 5.56. Did you pull your FSB and check it for alignment with the gas port and the diameter of your gas port? I'm pretty new at this, I pulled my buffer out and there is no markings on it to indicate the type. How do I know if it is an H or an H2? Also, at the FSB, the gas tube is pinned in there (not a screw) so I haven't knocked it out yet. I'm sure it wouldn't be too terrible to put back in place, but just to be sure, how dificult will it be to put back together? I've replaced the whole trigger assembly, so I feel pretty confident about my pin taking out/putting back in abilities. What should my gas port diameter be? And what do I do to check the alignment? I've pushed compressed air down the tube and didn't get any noticable leaks, so I figure that should be a good test for alignment. Anything else? |
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You have a short stroking issue, so need the detail on the rifle to solve that one. Again, before you jump the gun and start ripping down the rig, give us the details on the gun, such as manufacture of the parts, the configuration the gun is in, and if you have changed anything on it since new/factory build. |
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Again, before you jump the gun and start ripping down the rig, give us the details on the gun, such as manufacture of the parts, the configuration the gun is in, and if you have changed anything on it since new/factory build. Oh, right. CMMG upper and lower, DPMS trigger assembly, UMG handguard/rails, I'm not sure who made the bolt assembly, but I'd assume that it's CMMG. This is a hand-me-down so only the things I've replaces/have stamps I'm 100% sure I've replaced the handguard and the trigger assembly, the rest is how it came. It is the 14.5 inch carbine variation w/ collapsible stalk. Any other details that I've missed, let me know and I'll post |
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Quoted:
Quoted:
For carbine length gas systems, I tell people to start with the H buffer, as a minimum, with H2 for M193/M855 ammo. Some carbines need the H2 for both .223 and 5.56. Did you pull your FSB and check it for alignment with the gas port and the diameter of your gas port? I'm pretty new at this, I pulled my buffer out and there is no markings on it to indicate the type. How do I know if it is an H or an H2? Also, at the FSB, the gas tube is pinned in there (not a screw) so I haven't knocked it out yet. I'm sure it wouldn't be too terrible to put back in place, but just to be sure, how dificult will it be to put back together? I've replaced the whole trigger assembly, so I feel pretty confident about my pin taking out/putting back in abilities. What should my gas port diameter be? And what do I do to check the alignment? I've pushed compressed air down the tube and didn't get any noticable leaks, so I figure that should be a good test for alignment. Anything else? If there are no markings on the face of the buffer, you have a standard/non-heavy buffer. I agree with trying the H buffer. It will be marked with an "H" on the face. Unless you are using a suppressor, you wont want anything heavier than an H buffer. You will need a 1/16th punch for the gas tube roll pin. Piece of cake. Is the gas key plugged? |
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I run lots of lube. I lube all the places where metal touches metal: inside bolt carrier and bolt, outside of bolt carrier, and both sides of the charging handle. I put a little lube in the front of the upper, where the bolt locks into place as well.
As for the buffer, I looked and there was no H. I'll try and find someone who has an H buffer for me to try out and see if that has any effect on the ejection. As for the pin, I was reading about the pins in the FSB and that they are really tough to get out and in. Is this true for the gas tube pin as well? I have some punches, so that isn't a big deal. Once I get it out, what am I going to be looking for? |
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Don't put the H buffer in. Right now it is a waste of money for your problems. What the OP is experiencing is an UNDERGASSED problem. FTE "stovepipes" and the bolt not locking back are classic signs of extremely weak ammo, yet the OP is using NATO grade 5.56 ammo. Not an ammo issue. The only other cause is an undergassed system. The OP's AR is not getting enough gas to cycle his action (adding a H buffer would only decrease the amount that his action gets cycled already... which is basically nill as it stands). What else would cause the undergassed issues that the OP is experiencing?
OP, start with the barrel, take off the FSB and gastube, then inspect the gas system from the barrel all the way to the gastube. Make sure there are no obstructions and clean as you go. When you have the FSB back on the barrel pay attention to the alignment with the gasport. Next work on the carrier. Somewhere in your system there is a blockage or parts are not aligned (or there are faulty parts). Find the cause, fix your problem. |
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Quoted:
Don't put the H buffer in. Right now it is a waste of money for your problems. What the OP is experiencing is an UNDERGASSED problem. FTE "stovepipes" and the bolt not locking back are classic signs of extremely weak ammo, yet the OP is using NATO grade 5.56 ammo. Not an ammo issue. The only other cause is an undergassed system. The OP's AR is not getting enough gas to cycle his action (adding a H buffer would only decrease the amount that his action gets cycled already... which is basically nill as it stands). What else would cause the undergassed issues that the OP is experiencing?
OP, start with the barrel, take off the FSB and gastube, then inspect the gas system from the barrel all the way to the gastube. Make sure there are no obstructions and clean as you go. When you have the FSB back on the barrel pay attention to the alignment with the gasport. Next work on the carrier. Somewhere in your system there is a blockage or parts are not aligned (or there are faulty parts). Find the cause, fix your problem. Ok, I have the gas tube out and I tried for a bit to get the FSB off, but to no avail. I cleaned the outside and inside of the tube as best as I could. How do I check if the FSB is clogged w/o removing it? And when I'm putting everything back together, is there anything special I should do to make sure that there are no leaks? What else should I check while the tube is out? As for the carrier key, how do I check if it's clogged? I ran a flashlight down the key and all I could see was the end. |
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Quoted:
Also, at the FSB, the gas tube is pinned in there (not a screw) so I haven't knocked it out yet. The FSB pins can be driven out left to right. Quoted:
What should my gas port diameter be? And what do I do to check the alignment? The proper gas port diameter is 0.063". |
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Ok, I replaced the buffer and the spring, I got a new clip, I cleaned the gas tube and FSB as best as I could, I cleaned out the upper as best as I could, I had the head space on the upper checked, I had the bolt inspected (extractor claw and ejector, both seemed fine), and I made sure everything was super lubed. I took 3 different types of bullets with me to the mountains and fired several of each. Still there were some jams.
I did, however, take my wife with me and she filmed the whole thing. Thanks to the miracle of YouTube, I was able to upload the videos to be shared here for your inspection (and ridicule). Video 1: http://www.youtube.com/watch?v=TDB9HVgirJE I noticed that there was a lot of smoke coming from the front of the barrel. Maybe that might be something? I don't have the covers off my Red Dot (I know), the batteries were dead and so looking over the top was basically more accurate. Plus I was also trying to watch how far the casings were flinging out of the corner of my eye. Video 2:http://www.youtube.com/watch?v=x1mmk1J3SFE You can see how short the rounds are falling next to me. Video 3: http://www.youtube.com/watch?v=AS4FumzorP4 This video shows a jam. Notice the different angles of projection each one has. Maybe that is a symptom? Video 4: http://www.youtube.com/watch?v=PS-yO7l7ofU This one is an inspection of the casing before and after the round is shot. Notice the little scratches on the casing after it has been shot. I have all of the casings with me, so if you want a better picture of the casing, let me know and I can upload a hi res of the scratches. I hope these videos have clues to what might be wrong with my AR15 |
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The smoke coming from the barrel is probably just oil burning off from when you cleaned it. When you said you cleaned the FSB, did you remove your flash hider, then remove the FSB completely off the barrel, then clean it? If not, that would be another important thing to do... A way to check "alignment" would be to make a mark with brass (or chalk etc) vertically (with the line centered on where the hole for the gas port should be) on the face of the FSB, then make a corresponding mark where the gasport is located on the barrel. Aligning the vertical and horizontal lines should confirm whether or not your FSB is "aligned" properly. In your situation, you have a drilled FSB and barrel... if it was off, which I don't expect, you couldn't do anything to fix it with what you have. ETA I watched the first video a few more times and I'm not entirely convinced that is oil burning off... it almost appears like a "leak"  How was the fit between gastube and FSB when you took it apart and put it back together? Does/did it seem loose? |
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can you take a pic of the last case using macro settings? it looks like a really nasty indentation near the case head. have you replaced the extractor spring? does the bolt lock back after the last round is fired?
make sure you are not running a rifle length spring or buffer in that stock. |
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Your semi short stroking. Could be over sprung or over buffered, hammer binding, or even just a cleaning lubing problem.
As stated, check the recoil spring for length (should only be 10.5"),and make sure that the end of wind coils do not not have edge burs that may be scrapping down the inside of the tube. Next, pull the charging handle all the way back, and confirm that the face of the bolt does no retract back past the back of ejection port on a full charging handle pull. With the upper open, look at the back tail or the disco and the hammer. is there a white line/indent where the hammer tail has been tagging the crap out of the either one of them? On the buffer, have you installed a standard carbine buffer, or are you still running an H buffer? If an H still, then you need to replace it with a standard carbine buffer. also, on the carbine recoil spring, make sure it's a standard unit as well, and not a extra tension spring. Lastly, with a chamber brush and BreakfreeCLP, scrub the hell out of the chamber, then leave it in a dry state. Next, give the both the inside and outside of the B/C a healthy spray coat of CLP, give it a quick flick, then in that wet state, reinstall the B/C into the rifle, and try live fire again (read I want the upper bearing surface on the wetter side for testing, and want to confirm that the bolt locks back via the catch on the bolt face in that wet state. Note: use nothing else to clean the gun at this point, we want the only cleaner/lube to be CLP in the rifle. If you still have a problem, then either the key to carrier is leaking, the bolt is not exiting the barrel extension lugs correctly, or the gas port is too small to begin with. |
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Thank you for the comments!
"When you said you cleaned the FSB, did you remove your flash hider, then remove the FSB completely off the barrel, then clean it? If not, that would be another important thing to do..." No, I didn't. I couldn't get the taper pins off, but I really didn't try very hard. I will do this when I get a free day. I've read this can be quite the process! How was the fit between gastube and FSB when you took it apart and put it back together? Does/did it seem loose? It was a PITA to get off. It really took some man handling to both get off and put back on. It felt like there was a lot of resistance getting it on and off, so IDK how the seal is. can you take a pic of the last case using macro settings? it looks like a really nasty indentation near the case head. have you replaced the extractor spring? does the bolt lock back after the last round is fired? make sure you are not running a rifle length spring or buffer in that stock. I replaced the extractor spring and added an O ring to the assembly. The bolt did lock back after the last round every time. The new spring is 10 and 5/8 ths inches long, and the buffer is a carbine buffer. Here are the pics: http://imageshack.us/photo/my-images/33/dscn3837u.jpg/ http://imageshack.us/photo/my-images/804/dscn3838.jpg/ http://imageshack.us/photo/my-images/810/dscn3839.jpg/ http://imageshack.us/photo/my-images/685/dscn3841q.jpg/ Here is a picture of the hammer: http://img861.imageshack.us/img861/4348/dscn3848.jpg Everything else looks black. Those were the only parts of the hammer that were worn. I looked all over and nothing else had any indication of dragging or scraping. When the BCG is fully charged, the bolt is flush with the ejection port end. I will super scrub the crap out of the upper tomorrow morning and give it another go. Thank you for everyone's help! |
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When the BCG is fully charged (charging handle pulled all the way back), the bolt is flush with the ejection port end. That's a huge problem right there, The problem with the short/erratic eject paths of the spent cases is due to the spent cases tagging the back of ejection port on the way out,which they should not be touching. Either the receiver end of the receiver extension/ butt stock tube needs to shorted and re timed, or you need to add some fender washers (just lightly smaller OD that the tube ID) down the tube before install the recoil spring as a band aid. The face of the bolt should max out rearward around 1/4 to 3/8" in front of the back of ejection port. |
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That's a huge problem right there, The problem with the short/erratic eject paths of the spent cases is due to the spent cases tagging the back of ejection port on the way out,which they should not be touching. Either the receiver end of the receiver extension/ butt stock tube needs to shorted and re timed, or you need to add some fender washers (just lightly smaller OD that the tube ID) down the tube before install the recoil spring as a band aid. The face of the bolt should max out rearward around 1/4 to 3/8" in front of the back of ejection port. Hmmmm.... I can work on the butt stock tube. I'll find some washers and throw them down in there. How should I go about re-timing the tube? Is that something I can do or do I have to find a person to do it? I went again to the range today with Sessrumnir from the forum (who also has a really sweet setup. Very jealous) and these are the results: His setup: Ejection pattern = ~10-15 degrees below horizontal, same distance and placement for each shell My setup: Ejection pattern = no pattern. Sometimes forward, sometimes rearward, sometimes not at all. Different distances each time, but usually not very far. My lower, his upper and BCG: Same as his setup My lower and BCG, his upper: Same as his setup His upper and lower, my BCG: Same as his setup His lower, my upper and BCG: ~70-75 degrees above horizontal, same distance each time. He has a mid-length buffer tube and spring, and an H2 buffer. So, what I'm thinking is that the FSB and gas tube are where the main problems lie. I might try again at taking off the FSB, I just need to find a better punch and BMFH :) What I was wondering is, once I've taken off the FSB and cleaned it really well, how do I get everything to line up and sealed properly? The gas tube and the FSB were really snug, but how do I tell if there is a good seal? |
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Leave the FSB alone for now,
Try the fender washers first to see if that cleans up the ejection paths/jams. If that fixes the problem and you want something more permant than the band aid washers, then the receiver extension tube will need to be pulled off the receiver, and it shortened to achieve the correct bolt face retract point. lathing and milling is the correct way to solve the problem quickly and cleanly, but if push ca,e to solve, you could do such by hand You just need to shorten the tube enough that when you do have the face of the bolt retracting at the correct distance (spun in a few more winds), you do have the end of the tube just kissing the end of the buffer retaining center pin when the tube is also indexed for the butt stock as well. |
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Quoted:
Leave the FSB alone for now, Try the fender washers first to see if that cleans up the ejection paths/jams. If that fixes the problem and you want something more permant than the band aid washers, then the receiver extension tube will need to be pulled off the receiver, and it shortened to achieve the correct bolt face retract point. lathing and milling is the correct way to solve the problem quickly and cleanly, but if push ca,e to solve, you could do such by hand You just need to shorten the tube enough that when you do have the face of the bolt retracting at the correct distance (spun in a few more winds), you do have the end of the tube just kissing the end of the buffer retaining center pin when the tube is also indexed for the butt stock as well. Wow!!! I bought some $.17 washers from Home Depot, stuck on in the tube and went shooting this morning... No jams, all the casings were ejecting at the same angle, and they were landing several feet from where I was standing!!! Thank you very much Dano! After $50+ of (necessary) part replacements, all that was really needed was something less than a quarter... SOOO glad it's fixed! |
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