ARC Nucleus Gen 2 Sear Issues

[Donelan47]

Okay so I have been researching like crazy and see lots of different trigger issues and fitment issues between this combo but not this exact issue. If there is already a thread that covers this issue please point me to it.

I have a Nucleus Gen2 bought it as a barreled action from PVA and had them install a Timney Elite Hunter Trigger on it. I put it in a KRG Bravo. I've put about 300 rounds down the tube no issues at all. The last time I was out I noticed that depending on how I run the bolt I can make it so that the sear doesn't engage on bolt lift or in the rearward cycle of the bolt. When this happens and I pick up a new round it chambers no problem however the firing pin is already forward since the trigger never reset.

I have pulled the gun apart and made sure all screws are torqued properly I've relieved the trigger housing of the bravo with a dremmel and checked to make sure everything is clean and not greasy or gummed up with anything. I don't see any binding to my knowledge!

I have noticed that dry firing after I pull the trigger if I push forward on the rear of the bolt and lift it I can more repeatedly replicate the issue. I have not had any issues with slam fires leading up to this. I have drop tested the rifle to make sure the pull weight isn't to light. I did not mess with the trigger getting it from PVA. I don't know if they set it or if it's in a factory configuration. I do not have a pull gauge to test the trigger.

Anyone have experience with an issue like this?

 

[spife7980]

None of what you wrote makes any sense, in fact I’d say all of your understanding is backwards?

The sear will never catch on bolt lift or rearward travel, it’s not supposed to. It catches when you close the bolt handing the firing pin control off from the bolt body to the trigger.

If you are chambering a new round then the firing pin should not be forward, it should only be forward after firing.

I don’t see how pushing in the bolt after you’ve fired can effect anything since there is nothing to be done after firing except extracting.

So to surmise, I have zero idea what your issue is in the first place.

 

[Donelan47]

I believe it's cock on open if im not mistaken? So when I lift the bolt it does not cock and reset the trigger like it should. (It's an intermittent issues) there fore when I cycle that action and pick up a new round and chamber it. It's as if the trigger has already been fired. It never reset the trigger.

 

[Donelan47]

If that still doesn't make sense I can get a video and post it to try and better explain what i am saying.

 

[kindabitey]

Sounds like the trigger adjustment screw has loosened up. I had the same issue with my 223 Archimedes, and a Rem. 700 223. Both were
initially set at just over 1 1/2 lb. and backed off to less than 1 lb. One is a TT Diamond and the 700 has a TT Special.

 

[Donelan47]

Okay I didn't feel a noticeable change in the trigger at all but I will take a look at that to see if that's the issue!

 

[m1match]

When you lift the bolt handle, you are cocking the rifle on open but until the bolt is closed, the striker is held to the rear by the cocking cams on the bolt body. The sear on the trigger does not engage the cocking piece until you close the bolt. Some actions might have a little cock on close but my ARC rifles don't. By this I mean that (except for cock on close rifles like the Enfield) the majority is cocking is done on open, but on close the sear may engage the cocking piece slightly before the action is closed and there is a very slight cocking movement as the bolt is rotated closed.

I had a similar if not same issue with a Bix N Andy trigger in a trued Rem 700 action. Sometimes the cocking piece would not engage the top sear on close. I measured the distance from the trigger pins to the cocking piece like Bullet Central said to do and the distance was too great and I should need a high sear. However most triggers don't have the ability to change the top sear like the Bix N Andy.

Your Timney doesn't have changeable top sears, but your problem could be caused by other things too. The trigger adjustment is the more likely cause in my opinion. But, you could have an issue of tolerance stacking where your trigger is not compatible with your action. If you bought everything from PVA, I'd contact them to get their opinion on what to do.

 

[spife7980]

I believe it's cock on open if im not mistaken? So when I lift the bolt it does not cock and reset the trigger like it should. (It's an intermittent issues) there fore when I cycle that action and pick up a new round and chamber it. It's as if the trigger has already been fired. It never reset the trigger.

I think I’m understanding now, when you close the bolt the firing pin rides over top the sear sometimes. The only time the trigger and firing pin interact is when you close the bolt. All the rest of the time they are floating independently of each other in relative space. All the rest of the bolt throw until that very end has zero to do with the trigger.

As bitey mentioned, check your trigger adjustments. If your pull weight is too low or you don’t have enough sear engagement then the triggers internal springs won’t apply enough force for the trigger to hold the firing pins spring weight back when closing the bolt and engaging the two. Doesn’t look like the Romney lets you adjust the sear so pull weight is your only adjustment option, turn the weight up and if it holds then you know that’s the issue. A bixnandy will let you get really low

You can check the trigger itself independently of the action. I would press down on the triggers top sear and you can literally feel the sear catch and then fall away with your finger tips when you pull the trigger. If you can feel that sometimes it doesn’t catch but whacking it etc jars it loose and it behaves properly then a flush with lighter fluid could be in order.

 

[Forward543]

The firing spring is compressed, and the pin retracted, when the bolt handle is lifted. It acts on a cam in the bolt body. It does not engage the trigger sear until pushed back into battery, and the bolt handle lowered. You cannot have a slam fire, unless you have a failure of trigger sear and the sear on your striker pin, with the bolt handle lowered.
If your striker is not engaged with the trigger sear, you have an issue with the trigger and striker/ firing pin sear. Check the trigger for positive engagement.

 

[Donelan47]

Awesome thankyou guys for the information I will check those things this evening and see what I come up with. Also thankyou all for the basic mechanical operations of how they interact together! I'm learning something new today!

 

[Donelan47]

Okay so without taking the gun back apart right this second I wanted to replicate the trigger fail and here is what happens is that sear is sticking down is that a trigger weight issue or a flush the trigger with lighter fluid issue?

 

[whatsupdoc]

Most likely the trigger is either not adjusted correctly or broken. Send back to the MFG for inspection/repair or replace it.

Did you touch the adjustment screws?

 

[Donelan47]

No when I bought the barreled action pva installed it and sent it to me I just dropped it in the krg and went to town never messed with it other than made sure it was safe to use!

 

[kindabitey]

If it worked and suddenly it doesn’t work, something is broken. I concur with @whatsupdoc and go with sending the trigger back to the manufacturer.

 

[Donelan47]

Thankyou everyone for your help and education with this i sent the trigger back to timney and they got me up and running again. The trigger did have some broken parts in it and they fixed it and sent it back to me!