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Posted: 2/14/2013 9:33:19 PM EDT
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Old school JP fire control, from an old school person who has successfully installed a few going back many years, this problem is new to me ....
Trigger held back, hammer pushed back, releasing trigger releases hammer. (If I'm really careful I can sometimes get it to reset from disconnect to sear, but usually riding the trigger forward causes the hammer to drop on release.) Instructions and DVD say to remove material once from area B on the disconnector, the pad that rests on the trigger. Once only, no second try. WTF? Why not keep going a little at a time and try it as you go, as with dealing with the opposite timing problem? Do I need a stack of discos? All my other installs involved late timing not early. BTW, engagement is good, I even gave it a little extra after encountering this timing problem. |
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Lets first make sure that the trigger is set correctly before you start retiming the disco.
Starting with the back set screw, set the selector to safe, then screw the back allen bolt down until the back of the trigger snugs up against the bottom of the selector on safe. Here, flick the selector a few time from safe to fire to make sure that you don't have too much pressure on the bottom of the selector so you can't move the selector. Note: hammer has to be cocked back to set this set screw. On the front set set screw, get your hand in front of the hammer, and slowly pull the trigger. Screw the front set screw down until when you pull the trigger all the way back, the hammer is just released from the trigger. now with that screw setting, back the screw upward about 1/4 of a turn to give the trigger just a hair over travel after hammer release. Locktite both screws, and now lets move onto timing the disco. Trigger untouch, cock the hammer back until you get the back hammer sear and the disco sear as close as possible. Now the distance between the two is called the free gap. The free gap between the two should be in the .001 to .003 range (about that of a human hair). If you find the gap larger, then you will need to remove metal from the front/bottom of the disco where it seats against the top/front of the trigger. Hence, by removing metal from the front/bottom of it, it cams the disco more forward to close the free gap, Which in turn, makes the disco retain the hammer longer as you are releasing the trigger so the front trigger sear can get into the correct position to catch the hammer bottom lob sear on release from the disco. Note, I have a Jig that maintains the correct disco front/bottom angle to the hammer front/top, but you can free hand this with a diamond file it needed while making sure to maintain the needed angle so the to two surface maintain full contact. |
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I just watched the DVD again. It very clearly describes taking material off the bottom of the disco (B area) as a band-aid for taking too much from the nose (A area) and thus creating an early timing situation. Previously it described late timing and early timing, described how to fix late timing, but did not describe how to fix early timing. That was really annoying. Yes, all my previous JP triggers ended up having late timing. This one is early, now what?
Dano, you have quite the deviations from the instructions. The front screw is adjusted first, the back screw next, then the disco, and he safety isn't dealt with until last. Nonetheless, I'm going to try removing material from the bottom of the disco as you suggested. |
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When doing trigger jobs (from stock parts),
Its the take up from the trigger at rest, to off the bottom of the selector with no creep there that I set first (set screw up the pistol grip channel with the pistol grip screw shortened to allow this. Next is taking the free gap of the disco to back hammer sear down to .001 since we already have the trigger at home position set first step. Next true the trigger front sear, then true the hammer primary sear to the trigger sear while setting the engagement of the sears for Zero creep on release, while at the same time reworking the hammer bottom lob since we will have a great deal less trigger movement involved, and with reworking the bottom lob, the hammer bottom lob is going to contact the front of the trigger as the hammer moves to it's last at rest position. Then all that is left is to set over travel of the trigger after hammer release (set screw through the selector's fire position against the trigger tail), and as stated, I set in about 1/16" of trigger over travel after hammer release due to no matter how tight you shim the parts to the receiver, you going to have slight play and need to add the over travel after hammer release to make sure that the hammer is released every time. But with you having set screw, can pretty much attack the trigger take up to the selector set at safe, attack the trigger over travel after hammer release, the work back to disco free gap since you still removed all the take up to selector first step. But with now, once you have everything set, uncock the hammer and make sure that the hammer lob is not bindin/locking up on the front of the trigger as the hammer goes to full rest( up and forward). |
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Quoted:
Well that did the trick, first try with a stone. It's a bummer it turned out so stiff with the red hammer spring. You can adjust the hammer spring to lessen the trigger break weight. Just tweak the hammer spring right at the coils, not down on the legs, since if you tweak the hammer springs at the legs, the legs will ride up the side of the trigger C channels and loose retention to the annular grooves on the trigger pin holding it in place. 
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It worked, no doubles, no bounces, always reset...
http://www.youtube.com/watch?v=_U5Vtk6Jt6Y |
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