Big Bore Posted May 13, 2007 Share Posted May 13, 2007 At a match in Elko, NV yesterday my rifle started giving 2 and 3 round bursts. It has a JP trigger I installed in a bushmaster lower, it was put in last year it has maybe 2000 rounds since the install. When we checked it out at the match we could not find anything obvious, no debris in the receiver area, etc. The disconnector seemed to function properly when the trigger was pulled and the hammer was pushed back manually. The hammer reset properly after I let off of the trigger also. Any ideas??????????? Thanks, Link to comment Share on other sites More sharing options...
John Dunn Posted May 13, 2007 Share Posted May 13, 2007 Send it to JP. Link to comment Share on other sites More sharing options...
bigbrowndog Posted May 13, 2007 Share Posted May 13, 2007 Be more consistent in how you pull and let off on the trigger, let off the trigger more agressively. even a correctly installed, properly working trigger can double, if you "float" the trigger. A good friend of mine, "nameless 1", loans his AR with a correctly working JP trigger, to another of our good friends "nameless 2", and it doubles when he pulls the trigger. We have deduced that it is the loose nut behind the trigger, because it only does it when "nameless 2" shoots the gun. If however your gun does it when others try, then by all means return it, or if you installed the trigger, have it looked at by someone else. "nameless 3" Link to comment Share on other sites More sharing options...
EricW Posted May 14, 2007 Share Posted May 14, 2007 (edited) Check for debris on the sear/hammer notch. I got a single chunk of something (sand? corncob?) jammed in the sear notch and it caused my JP trigger to malf - but in a different way. One of the consquences of using the reduced-power springs on a JP trigger seems to be more susceptibility to gook. Edited May 14, 2007 by EricW Link to comment Share on other sites More sharing options...
Chills1994 Posted May 14, 2007 Share Posted May 14, 2007 Big Bore wrote: ...yesterday my rifle started giving 2 and 3 round bursts... SSgt Sykes says: "Hu-ahh! Get some! Get some!" Link to comment Share on other sites More sharing options...
Dan Sierpina Posted May 14, 2007 Share Posted May 14, 2007 Trapr is right!!! Any trigger in a semi auto can double if it's been worked on. "Milking" the trigger will do this. Do Not try to shoot it like a bolt gun! Your finger does not have sufficient tension on the trigger for the disconnector to work when the small amount of recoil takes place. Your finger then bounces and pulls the trigger again. My AR will do this only when I forget, when shooting off a rest. The gentleman that taught me to accurize M1a's told me that it would happen on them and M1's too. Link to comment Share on other sites More sharing options...
RiggerJJ Posted May 14, 2007 Share Posted May 14, 2007 Otherwise known as "bump firing", sometimes happens to me on short hoser stages. Its all in the trigger finger and the way the rifle is held. At the height of my problem I could get it going then take my finger off the trigger and it would keep going for 2-4 rounds. The rifle had to be heavy (re; C-Mag in a mid weight 20inch upper) on a bipod and held loosly to allow it to get rocking. There was nothing wrong with the fire control system. (read, there was NOTHING WRONG with the rifle.) How I fixed it? A titanium firing pin, a stainless light weight carrier (IE, tuning the rifle to me) and just learning how to use it. It/I will still double maybe once or twice every 6 months, but it doesn't eat up a C-mag worth of ammo anymore like it used to. What I think happens most of the time is the mass of the bolt coming forward moves the entire gun forward and smackes the trigger against your trigger finger, the fire control system will have reset and is waiting for you to pull the trigger again and....bang....bang....bang! It sounds like it goes full auto because that is basically how fast a M-16 on auto fires...but actually you are getting just real fast splits! jj Link to comment Share on other sites More sharing options...
hopalong Posted May 14, 2007 Share Posted May 14, 2007 I freaked out one day while testing my National Match M1a off sandbags and it doubled(or I thought it did). After doing it another time about 20 shots later I deducted that since I hold it so soft while on bags it actually reset the trigger on the rearward recoil impulse, bouced off my shoulder enough to press trigger again for round number 2 and by then I would stop the rifle to keep round #3 from going. I had really thought I had broken my new expensive rifle. I have not had that problem with any of my AR platforms, including the National Match Bushy..........but maybe for you.? Might be that they don't quite recoil like a M1a either. Hop Oh, and call JP or Benny Hill and see what they say. Link to comment Share on other sites More sharing options...
Dan Sierpina Posted May 14, 2007 Share Posted May 14, 2007 Hopalong, That's exactly what happens. The cure....a crappy trigger (stock) or very simply pull the trigger through like you mean it! Link to comment Share on other sites More sharing options...
Big Bore Posted May 14, 2007 Author Share Posted May 14, 2007 (edited) It seemed to only do it when I was shooting from a position where I had the rifle directly on the wood in a port. I am running the JP lo mass stainless carrier and buffer on a 20" barrel set up for shooting irons. The RO got kinda of upset with the auto action even though I tried to explain that I had have some goverment financed training in that area. So I finished the match with my buddies lower which has A JP trigger also and I had no trouble. I will call JP and see what they think. Edited May 14, 2007 by Big Bore Link to comment Share on other sites More sharing options...
CraigS. Posted May 15, 2007 Share Posted May 15, 2007 I also had this same problem . The easy fix is to very slightly back off the rear set screw the rear set screw sets the hammer and sear engagement depth. If any debris gets under the rear screw, it will reduce the amount of sear engagement. This adjustment will also increase your take up travel as well. craig Link to comment Share on other sites More sharing options...
Front Man Posted May 15, 2007 Share Posted May 15, 2007 I had to do a lot of filing to fit a JP in my Bushmaster. I think I had to get into the softer steel to make it work. FM Link to comment Share on other sites More sharing options...
BillL223 Posted May 15, 2007 Share Posted May 15, 2007 I've been shooting a JP trigger for years and had some doubling in a BM lower with a trigger JP installed. I called them and they checked my records and noticed that I had a low mass bolt carrier (aluminum) and advised a titanium firing pin. Bought one from BM and the problem disappeared. Link to comment Share on other sites More sharing options...
spd522 Posted May 27, 2007 Share Posted May 27, 2007 My SP1 lower with the JP did it once too. 2-3 rounds everytime I pulled the trigger. Everyone behind me was yelling " I want to shoot it next". Turns out the hammer pin had worked it's way in and was no longer in the receiver hole on one side. So complete engagement wasn't happening. Kind of fun though. I have had doubling when holding the rifle loosely with a light trigger. Another also did it when releasing the trigger very slowly after a shot. Remedy was a slightly heavier spring. Link to comment Share on other sites More sharing options...
George Posted May 27, 2007 Share Posted May 27, 2007 Bump firing of multiple round bursts in match stages when the fire control system checks out fine is typical with a very lightly set JP trigger group. The best solution is more sear engagment and reset, or learn how to shoot it with a more purposeful trigger finger. This happens mostly when pussy-footing the trigger and having the gun rested can exacerbate it if you have a full weight bolt and recoil system as Rigger JJ stated. A Ti firing pin can help but is not the cure. It is mostly the nut behind the bolt that causes this. I can make mine do it on cue if I soft-hold the gun and loosey-goosey the trigger stroke. Link to comment Share on other sites More sharing options...
kamicosmos Posted May 31, 2007 Share Posted May 31, 2007 Well, just to counter the technique replies, throw a trigger pull gauge on it and see if it is where it should be. My Bushmaster 2 stage trigger starting going burst on me at a carbine course. Turned out the sear wore prematurely. Had to replace the hammer. Guage was showing under a pound! Since it was a gradual reduction in pull weight, I just got used to it. Side benefit is I have pretty good trigger discipline(sp) on my AR now, a stock trigger system feels so heavy! (I admit to knowing nothing about the JP trigger, so if I apologize if I'm missing something specific about them and going burst easy.) Link to comment Share on other sites More sharing options...
George Posted May 31, 2007 Share Posted May 31, 2007 The JP gunsmith in kits and both the JP and McCormick drop-in units are horses of a differnt' color compared to ALL other trigger groups in existence. Even the Jewel is not quite the equal of the crispness that can be had in a full install kit JP trigger system. The JP and McCormick cane be safely set for sub 2lb pulls and almost no takeup, or reset throw. The metal is not surface hardened like most are and it holds it's way better than anything else out there. That said, all things wear and 12-15k is about where the JP metal needs to be replaced IME. Not bad for a sub 2lb trigger with no slack, creep, or slop at all. The bump-fire issue is pretty much a second/third trigger pull thing from the rifle movement against the shooters trigger finger. Loose grip thing! Link to comment Share on other sites More sharing options...
Big Bore Posted May 31, 2007 Author Share Posted May 31, 2007 I took it out and tried to get it to burst fire again and could not get it to repeat. I called JP talked to them and checked out the obvious first and decided it is slam firing since the shots were so fast you almost could not distinguish the shots. Ordered a titanium firing pin , and I will see if it repeats at the Ironman. Link to comment Share on other sites More sharing options...
Mick Posted June 1, 2007 Share Posted June 1, 2007 If however your gun does it when others try, then by all means return it, or if you installed the trigger, have it looked at by someone else. To get a JP to run really light and reset like a pistol, a little work on the disconnector to fit it just right ocurrs. Sometimes you just need to fit a new disconnector so the hook gets the hammer before it fires again but it takes some special attention...I have to redo Buddy #1's disconnector and then set up his DPMS 308 too. My JP has over 10,000 rounds on it and will give ME .11 splits but might double ofr others Link to comment Share on other sites More sharing options...
PacMan Posted June 5, 2007 Share Posted June 5, 2007 (edited) I think we are talking about 2 different issues here - #1) Bump fire, and #2) Slam fire. Bump fire is when the rifle is held loosely against the shoulder pocket and upon recoil, albeit very minor with .223 and efficient brake, the gun would bounce forward off the shoulder and since the finger is still there in position from the previous shot, it would trip the trigger again, all in a fraction of a second. Happened to me at CMMG match and sure sounded like a full auto . George said it well "It is mostly the nut behind the bolt that causes this" Slam fire is when the firing pin has enough forward inertia when the bolt goes into battery and ignite the primer. Seemed to happen more on the super light JP alum bolt carrier & short buffer set up. Edited June 5, 2007 by PacMan Link to comment Share on other sites More sharing options...
RiggerJJ Posted June 5, 2007 Share Posted June 5, 2007 (edited) Yep... at the time mine was doing both slam fire and bump fire. jj Edited June 5, 2007 by RiggerJJ Link to comment Share on other sites More sharing options...
PacMan Posted June 5, 2007 Share Posted June 5, 2007 Yep... at the time mine was doing both slam fire and bump fire.jj Yea, but you are in "Open Class" so anything goes If the problems still occuring, I will send you two (2) new in wrap DPMS mil-spec fire control units in trade for your "faulty" JP fire control unit Link to comment Share on other sites More sharing options...
RiggerJJ Posted June 6, 2007 Share Posted June 6, 2007 Never said my JP fire control system was faulty... It was a combination of the nut on back of the stock, and replacing the bolt with a lightweight bolt and titanium firing pin... Works great now! no slam fire OR bump fire... Hung, Before we trade I want to see you use one of the mil-spec units in your rifle in the next match you shoot, just to make sure they work. jj Link to comment Share on other sites More sharing options...
ChrisStock Posted October 20, 2008 Share Posted October 20, 2008 Had this happen to me with my new AR build at the range yesterday. All excited, set up on a 1,000 yard range, whipped out the bipod, got a sight picture, and bambambam. I broke it open, performed a quick inspection, then a function test, and everything seemed ok. Calmed down, sighted in on a 300 yard target, and got a double.. then another double. &^%! I then shot at a 100 yard target from the standing position for several shots in a row, and everything functioned normally. I sat back down at the bench and sent another triple downrange. I was able to deduce that it was a combination of me being veerrrrry gentle on the trigger pull, coupled with it being shot from a bipod off of a concrete table with the movement after recoil just enough to get it to reset and fire again in hundredths of a second. I am unable to get more aggressive on the trigger pull when sighting in on a target at distance over iron sights like that, lord knows it's hard enough to hold a sight picture on a target that distant without me jerking back on the trigger like a misbehaving dog's leash. It is a stock Del-ton lower kit, and the trigger is pretty sweet, but I will have to figure out how to make the reset a bit longer to alleviate this unless I find something else that can be done. I'm in a tad over my head with this one, as getting it together and running was challenge enough. Just another joy of AR ownership to contend with, I reckon. On the plus side, I started engaging 12" plates at 100 yards and hit 27 out of 30 with my M&P .40 with my new load that I am planning to use in Limited. I had to do something fun while I was there and the opportunity was too great to pass up. Lesson learned. Link to comment Share on other sites More sharing options...
ChrisStock Posted October 20, 2008 Share Posted October 20, 2008 (edited) accidental double burst...again Edited October 20, 2008 by ChrisStock Link to comment Share on other sites More sharing options...
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