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Posted: 12/30/2013 3:18:50 PM EDT
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Hello there. I am having some issues with my new build and I am hoping somebody here can help me out. After over a year I finally finished my first AR build. My issue is when I am pulling my bolt back. I can feel it drag at the last inch or so of pulling the charging handle. I have narrowed it down to an issue between the safety selector and the hammer. When the hammer is cocked and the safety on is when I feel the drag. I can push the hammer down just a little when the safety is on, I can push the hammer down about an 1/8 inch, when safety is off I can push the hammer down about a 1/4 inch. When the safety is off I can pull the charging handle back and there is no drag. I assume the the hammer is not going down far enough when the safety is on to let the bolt pass smoothly. I changed out the disconnector spring, trigger spring and hammer spring, along with the disconnector itself.
Just to recap when I pull the charging handle I can feel the bolt drag, when a mag is in this dragging will cause the rounds not to feed, the bolt will stop and I have to use the forward assist to get the bolt to go forward. The lower is an R-Gun lower with R-Gun parts kit. Bolt and Carrier is DPMS. Upper is Palmetto State Armory 5.56 Is there any chance something is not right on the lower itself? Hope I gave enough information. Please e-mail me if you have any questions. [email protected]. Thank you |
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Are you pulling the charging handle back all the way and then let it go?
That is the proper way to put a round into battery. If your riding the bolt forward you will have exactly what your describing and eventually will cause issues. The bolt will drag some, just lube up all the parts and when you pull bolt back, let it go. |
| I pull the charging handle back all the way and I can feel it drag at about the last inch or so of pulling it back. Letting it go it drags a little and then snaps forward. Sometimes if I ride the bolt forward I can get the bolt to stick where it drags for a second. I have tried lubing the parts and it still drags. I can try to take a video if needed, either that or if somebody wanted to skype or something I could so you. |
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Hammer Drag is normal, and is the bottom of the carrier lowering the hammer sear down below the disco sear. But post a photo of the bottom of your carrier, and the hammer top contract pad edge.
What is not normal would be more tension needed to pull the charging handle back the last inch, since this could be the wrong recoil spring in play and coil binding out before the B/C makes it all the way back, or the tail of the hammer binding up between the bottom of the carrier and the tail of the trigger/disco. Also to point out, pull the bolt from the carrier, and dry fit the carrier with key alone into the upper. With this, you can check to make sure that the width of the carrier key is not to wide for the upper receiver slot, and even to confirm that you have the gas tube correctly aligned with the key. |
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So here are a couple pictures of my BCG and hammer. As you can see there is some rubbing going on. I don't feel this to be normal but this is my first AR I have built/owned.
http://imageshack.com/a/img22/505/k2j0.jpg http://imageshack.com/a/img36/5493/e8m3.jpg |
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From the pics, the marks you have on the bottom of the bolt carrier and top of the hammer are normal. After the gun fires the hammer will be forward. As the bolt carrier assembly unlocks and travels rearward extracting the empty casing, it is also cocking the hammer (meaning that the bottom of the bolt carrier is pushing the hammer rearward) and you will see rub marks like you have where the metal of the bottom of the bolt carrier is rubbing against the face of the hammer. A little lube on the bottom of the carrier will help reduce some of the friction, but not all. If you manually cycle the action back and forth without firing it, the hammer remains cocked back so you have a little less resistance, but you will still get resistance at the last inch or so of the manually cycling as the bottom of the bolt carrier is pushing the hammer down a little as it travels over it. The only thing I see in your pic (but it is hard to tell from the angle to be sure), is that it looks like your right hammer spring leg might be on top of the trigger and not the trigger pin.
CY6 Greg Sullivan "Sully" SLR15 Rifles TheDefensiveEdge.com (763) 712-0123 |
| Thanks for the reply. I understand there would be a little drag due to the bolt going against the hammer but I do not understand why it is different when I put the safety from Fire to Safe. On fire there is no drag at all, on safe there is a lot of drag. I will try to get a couple pictures this morning of the hammer difference from each one. |
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Quoted:
Thanks for the reply. I understand there would be a little drag due to the bolt going against the hammer but I do not understand why it is different when I put the safety from Fire to Safe. On fire there is no drag at all, on safe there is a lot of drag. I will try to get a couple pictures this morning of the hammer difference from each one. The bolt is the thing at the front that locks into the barrel extension. The part that lowers the hammer back is the bottom of the carrier. So you have the carrier with key bolted to it, the bolt with ejector and extractor that goes into the front of the carrier, the cam that holds the bolt in the carrier, the Firing pin which holds the key in place, then the firing pin retainer that holds the firing pin in place. I state this since if the bolt is making contract to the hammer, you have huge problems on hand. 
Now to add, would help to get a side view of the hammer. I ask this since the top of firing pin contact pad on the hammer looks to be real funky. Trust is, you will find one of two semi auto hammers in a kit. One is the standard L top cut hammer, while the other is really just a M-16a2 round top hammer with the auto sear tab ground off. On the mod'd M-16 hammer, you can tell this by looking at the back disco sear, since it will be wider on the ejection side that the other side. On your hammer, looks to have started out as M-16 hammer, but someone did a top grind to the contact pad, and this leading sharp edge may be what is causing the excess binding (instead of gliding) of the carrier as it move back forward against the hammer. Mod'd M-16 hammer to semi, 
L cut semi hammer against a umolested M-16 hammer, 
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