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Posted: 9/26/2008 5:54:23 AM EDT
| I've built numerous AR-15's and recently assembled one from parts that a co-worker ordered from blackthorne (I know....No shock here that there is a problem) and everything seemed fine when I completed the build. Several shots were fired without a problem right after it was built but a few weeks later he came to me after having problems at the range. The rifle was said to fire a shot and then not fire again without pushing the trigger forward to reset the trigger. I function checked it and it does not move forward and click when reset every time. I'm just wondering if it's the sear, the trigger, or the hammer that is the most likely cause of the problem. I do notice that the trigger pull is very light and feels like it's about a 2 lb trigger pull if that matters. I liked the feel of the trigger, but it may be related to the failure to reset. Any suggestions would be appreciated. The lower is DPMS brand and the lower parts kit came with the blackthorne kit. I inspected all of the parts and everything looks as new with no visible wear. No obstructions were found in the trigger area and everything was good and clean, although pretty well soaked with some sort of lube. |
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Pull the FCG, and confirm that all the spring are installed in the correct oritation. While the parts are out, check for debris from a blown primer. With the parts are out, check for burs on the leading edges of the disco and trigger secondary sear, and the sides at the trigger C channel for burs (that may not be allowing the trigger to slip on the pin). As for the light trigger, if using stock FCG parts, there is something amiss since the trigger pull should be in the 6lb range. Here alone, sounds like some of the springs where not installed correctly or beyond tweaked, and causing the problem with the reset alone. If you need the guide, front/first page of ar15.com (www.ar15.com), bottom left will be the links to the the needed guides and build information. www.ar15.com/content/guides/assembly/lower/ |
| Thanks, the first thing I checked was the proper position of the parts. I thought my co-worker may have pushed the trigger or hammer pin out instead of the rear takedown pin on accident and caused the springs to be in the wrong position. He really didn't know how to break down the weapon. I checked for stray primers and inspected the hammer, trigger, disconnect and springs and all look fine with no burrs. I suspect that one of the small parts is out of spec somewhere because I've built dozens of these things with parts from reputable companies and have had no problems except for the kits people have brought to me that were bought on Gunbroker or directly from blackthorne. The universal problem with their kits seem to be improperly staked gas keys though and this isn't the case here, although I did go ahead and use Loc-tite on the screws that turned out with an allen wrench without any effort. |
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Loctite on the key (surface of the key to carrier) works great to create a gasket if you have small leaking, but will not keep the screws tights due to the heat. Simply, the key needs to be restaked to keep the screws from backing out again. www.ar15.com/content/page.html?id=122 AS for the trigger not resetting, being that he can push the trigger forward, it does not sound as if the pistol grip screw is too long (protruding into he bottom of the receiver cavity and pressing up on the trigger), nor that the back of the trigger is too tall (back of the trigger maxing out against the selector before the disco can release the hammer), but don't weed these problem out if when the trigger is pushed forward, it only travels just enough for the reset (read no creep once the trigger is pulled to hammer release). I am guessing that you have checked everything else for burs and are confident that the trigger is at least moving as far forward on it's one that binding for the most part is not occurring? |
| The travel of the trigger seems fine, but the spring doesn't seem to push hard enough to reset every time. I'm wondering if the spring wire guage or size isn't correct. There is a bit of travel in the trigger moving forward and as it is pulled so I don't suspect the problems mentioned. I'm going to try replacing the springs and disconnect first and see where it goes from there. The catch surface on the back of the hammer looks like it may also be less than on the Double Star hammer, but it appears to catch just fine. I'm going to swap the springs and disconnect and if that doesn't work I'm going to suggest that he buys a few small parts from a reliable source. Thanks for the replies. |
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Pull the trigger pin and trigger, and with just them in hand, confirm that the trigger rotates freely on on the pin. Next install the disco and spring, and check rotation again. Chances are you find that there is either a bur there in the works preventing return, or burs on the edge of the disco and hammer secondary spring not allowing the trigger to fully return to back at rest. |
| The parts are installed properly. The 1st thing I did was to function check it before I gave it to him. He shot it and it worked fine the first day, but then a few weeks later he started having problems with it. I'm getting the rifle back from him today and I'm taking it apart to check to see if the inside of the pin holes are smooth. I'm leaning towar a burr inside the holes because the outer surfaces were all smooth. I'm also going to look for debris that I may have missed when visually inspecting the weapon with the small parts in place. |
| I got a chance to look at it under better light a my home (instead of under car headlights in a parking lot) and took apart all of the trigger group parts. The first thing I noticed was that there was absolutely no oil on anything. I had lubed it up really ell upon assemble so I was wondering why everything was so dry. It turns out that it was sprayed down with Brake-Kleen after the first few shots were made and never lubed again. I took the parts out and the pins didn't pivot very smoothly due to the parts being dry and somewhat gritty feeling, kind of like a very fine sandpaper feeling on everything but the polished surfaces. I didn't notice any debris, other than the dusty looking residue from the brake-kleen. I lubed everything generously with CorrosionX and reassembled everything. Everything is working fine and the trigger is resetting flawlessly now. It had been resetting about half the time before, but did so slowly with a delay sometime. I hope a little conversation about not hosing down a gun with parts cleaner will solve any future problems. I guess I shouldn't have rushed judgement on his blackthorne parts, but after all of the negative things I've seen posted I was pretty sure that it was going to be a problem. It still has really poor bolt key staking, so I'm sure he'll have to address that soon. |
| scroll up and check 1st link posted by Dano523. It's a link to the guides area of AR15.com and it includes directions on how to assemble the whole lower from parts. All you have to do is push the trigger and hammer pins out from either side and visually inspect the assembly. Check for worn or broken springs and debris. Also look inside the holes where the pins fit and make sure that everything is lubed very well when reassembling the lower. It shouldn't require any tools, other than something smaller than the diameter of the pins to push them out. Assembly is just as simple. Just pay attention to the orientation of the springs in the diagrams and you shouldn't have any problems at all. |
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