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Posted: 5/28/2007 7:09:21 AM EDT
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Hi all, I hope this is the right place to post this. I have an old Bushmaster Assault rifle with the AR FCG. Ussually shots okay for an old POS. he Last range trip, it would fire the first round, and weapon failed to cock the hammer on the next round. I did the functions check and it fails on the second portion (hold trigger, charge weapon, release trigger, pull trigger). The hammer follows the bolt up. If I breakdown the weapon, and manually do it by holding the trigger and pushing the hammer down it will catch and perform the check fine. But it seems I have to push the hammer way down before it engages. I thought it was not fully cycling, but the spent round is ejecting, and new one feeding properly. So....I replaced all trigger components and safety with new ones from Bushmaster (just stock FCG). Same result with the function check. I can remedy this by pulling the charging handle back about a half inch and it does recock the hammer, as long as the trigger is released. It only fails when the trigger is held back. That darn hammer will not stay cocked. Any help would be appreciated. I`m about ready to retire this thing. Thanks! joe |
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Is the spring under the back part of the disconnecter (i am assuming the disconnecter is installed)? All i can think is that the old unit broke and fell out, and the new unit was installed without one. With new parts, that is about the only thing i can think of at this point. That is, baring defective new parts. Did you buy the parts as a complete FCG or just the pieces you needed? Did you get them ALL? Edit to welcome you to the site. 
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Thanks for the welcome! Been a long time lurker. ht Yeah, the disconnector is installed with the spring, wide end inside the trigger. I took it all apart several times just to make sure I was installing everything right and followed the assembly guide too. I have several spare parts for this and I thought I would rotate parts in and out just to make sure I had no "problem parts". I ended up putting all the new parts back in. I guess for the $190.00 I paid for the rifle back in 1991, I`m still pretty far ahead. Maybe I`ll just have the finish redone and sell it to someone who lusts after Bushmaster memrobilia. |
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First off welcome to the site!!!! Now lets get done to the grit of it, The old FCG sounds like it needed the disco retuned if the parts where still in working order. If the second FCG is doing the same, releasing the hammer at trigger release, then it too may need to have the disco tuned to the rifle as well. Now before I start to write the novel on how to tune a disco, I need you to go to the information button on the top left of the screen, then weed through it under guides, then to assembly, then to lower assembly. Double check all the parts/spring to make sure that you have installed/orientated them correctly first. |
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Thanks for the welcome! hat Just to clarify though, from the guide.... FUNCTION CHECK "Without releasing the trigger, push the hammer back again and verify that it locks (caught by disconnector)." This is where she fails during an action cycle, as long as the trigger is held in. If the lower is seperated and I`m doing this by hand, I can push the hammer down and it finally catches, but it seems I`m pushing the hammer farther down then the carrier would ever cycle it. You threw me off with the line you wrote "releasing the hammer at trigger release." I just wanted to clarify the issue. |
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First, I need you to confirm that the FCG is the .154 set, and not the Colt .171 set. The FCG pins should fit semi tightly in the receiver holes, and the FSG holes should fit semi tightly to the pins. With that out of the way, lets function test this way with the upper and lower locked together. Hold the Trigger back, and charge the weapon. Now slowly release the trigger and re-pull it. When you released the trigger slowly, the disco should have released the hammer, and it was caught by the trigger sear. On the second trigger pull, the hammer should have fallen and struck the FP. Next, hold the trigger back again, pull the CH, and with a third hand, lock the Bolt back on the catch. Now with the trigger still held back (hammer still retained by the disco), hit the bolt catch and let the B/C slam home. Now again, release the trigger slowly, and then pull it to release the hammer to strike the FP. If the rifle/FCG fails any of these test, I need you shotgun the upper open, the lower the hammer by hand until you can get the hammer and disco sears as close to each other with the trigger still at rest. The gap between the two should be in the .001 to .002 range, and if the free gap is much larger than this (read not just barely kissing), you will need to retime the disco. Also to point out, if the disco will not release the hammer on either test, then you will need to check the hammer and disco sear for leading edge burs. If burs are found, clean them up with a stone to allow a clean release. To save from having to post again, To retime a disco, you will remove metal from the bottom front of it where it rests on the front/top of the hammer. This will allow the disco to cam more forward, and will take the free gap between its sear and the hammer sear. Again, your looking for a gap of .001, which will be the two sears just about kissing at trigger rest. What this does is allows the disco to have more gripping tension to prevent bounce releasing when the carrier slams home, and at manual reset (you releasing the trigger) allow the trigger primary sear to get into a better position to catch the hammer from the disco release. P.S. I meant to post this last night but my Internet connection or the server went bad (read I pretty sure it was "The Flightless One" again with a boot leg version of Frogger this time killing the system. We keep mugging him every time he shows up at the office to check for boot legged software that may be infected, but since no one will do a B-C search on him, he’s still getting it into the building.  |
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Thank you very much for the info! he After I checked the disconnector timing, everything was in spec. When I was watching everything as i cycled the action, it seemed the hammer was not being pushed down very far by the carrier. Now, my Bushmaster is the old, old, old Bushmaster Assault rifle (think Arm-gun), but uses all AR FCG parts, mags, grips, and so forth. Sorry for any confusion there. But with the weapon assembled, you can watch the cycling through the side. I examined the carrier, and the area that actually cocks the hammer during cycling is worn-out. It has enough meat to lock the trigger down but not enough for the disconnector. I verfied this by placing 2 layers of blue masking tape across this area, I re-assembled the weapon and performed a functions check. Worked perfect. Since Bushy no longer has any parts for this thing, it`s time to retire it, I don`t wanna take any chances by shooting a rigged-up weapon. Wife felt bad for me and said I could go ahead and start building an AR for my fathers day gift.hink |
Keep in mind that this in not an AR rifle. Best guess is that the upper has worn out, and the reason that carrier is riding higher. Since Bushmaster has not offered this type of rifle for a long time (read three companies ago), and no longer has parts, it's just time to take the rifle out of service. Yes it could be a project rifle, but it can wait since the wife has cracked the checkbook open for a new build. 
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