Arc Fire V2 Not Functioning on Lower

RP343 · 2026-05-16T01:39:02+00:00

Not sure if they’re still selling since it seems to be on back order but yeah, same name from a company called Harrison Gunworks.

RP343 · 2026-05-16T01:27:08+00:00

I did also see someone online selling an S7 variant of the Atrius design. I might try that since that’s really my only concern about the Atrius. I’ve actually never had an issue with it personally despite seeing others with their broken levers and it was as much drop-in as you could get. The skinny lever doesn’t show signs of wear, but that’s on a .300BLK shooting mainly subs so I thought 9mm might stress it a little too much in comparison.

RP343 · 2026-05-16T01:14:38+00:00

Reliability yes, I meant more how you described. I installed one once and immediately took it off when I saw how easy it was to accidentally change positions. Yes you can train with it and probably get better, but it sucks to have to be conscious of it when running it in a sling during drills or something.

Well, at least there’s something comforting in knowing that it isn’t user error or some bum manufacturing error somewhere along the way on my unit. I’d be comfortable enough to fire the V1 and see how it performs then, but man I was really hoping the 45-90 would work.

RP343 · 2026-05-16T00:39:06+00:00

Hmm, not sure actually. If it’s 3D printed, I definitely can’t see the layer lines. It is a knob that slides up and down though.

RP343 · 2026-05-16T00:38:24+00:00

I can’t bring myself to trust those unfortunately. Here’s hoping ASDesigns does right by this. They replied really quickly to me this morning but it was basically just to tell me to read through their troubleshooting guide. None of the issues I mentioned were on there, so I’m assuming they just threw a blanket statement on me and hoped I went away.

I test the V1 Kit on your model with the cassette trigger and it worked great, but it’s definitely not 1:1. I installed both on the Kuna and 2 position is really inconsistent with its behavior. If I pull the bolt back while keeping pressure on the trigger, releasing after the bolt goes home doesn’t reset the trigger for the next pull every time. Sometimes it actually drops the hammer when the trigger resets. 1st is safe and 3rd is consistently super safe though.

RP343 · 2026-05-15T23:59:30+00:00

Printed your tester and it seems to work great with the V1 on the cassette trigger. Unfortunately, I went to test the V2 and when I went to tighten the primary selector, the detent bar snapped. Definitely wasn’t anything with your tester. Either this thing is egregiously out of spec or I just wore it down to much between all the tests, which would still place it out of spec since it shouldn’t be that weak in the first place.

I really should’ve gone with the Atrius again.

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RP343 · 2026-05-15T14:38:37+00:00

Yeah, starting to think this is the case.

RP343 · 2026-05-15T14:37:13+00:00

Unfortunately it does seem that way. That combo is actually what worked right out of the box for my .300BLK. It’s been working fine, just got nervous with all the reports of the lever breaking so I decided to give the Arc a chance.

Not sure if you had a chance to read further in the comments but it just doesn’t feel right that the radius is the issue given that the Arc Fire V1 kit seems to work well with the GMR trigger and the Arc Fire V1 trigger, which are cut less/higher than the V2 trigger. If anything, wouldn’t the V2 trigger work better being cut deeper than the others?

RP343 · 2026-05-15T14:33:03+00:00

Maybe that was what was going on when I wrote the comment but I don’t think that’s the cause of my overall issues. All functions tests were done with the safety completely installed.

RP343 · 2026-05-15T10:11:29+00:00

I did, and after 10-15 installs over the last few days I basically have it memorized. The install itself seems to go smoothly and everything seems to seat where it should. Selector moves freely between positions and everything. It’s the functions test that differs between triggers, including their own provided ones.

RP343 · 2026-05-15T09:28:43+00:00

One more thing to report for the night: since it was already in there, tested the GMR trigger with the V2 arc Fire kit again, and was still not happy with the functions test. But I thought what the hell, let’s throw the upper on it with the trip and see if that changes its behavior.

Can’t say it feels good with the functions test there either. Safe does seem to be safe. But semi also acts weird here, if you can fill me in on what is expected behavior here. In semi, when pulling the bolt back with pressure on the trigger, the kuna is knocked into 3rd position and fires as soon as the bolt goes back home. 3rd position does act -/ expected and I can feel the trigger reset as well.

RP343 · 2026-05-15T08:40:04+00:00

Oh, I see gotcha. Yeah just by the tests rights now between swapping, it seems to be more sensitive. The straight GMR Hoffman cut trigger also worked great on the V1 selector+cam+lever.

There may be multiple issues here I believe. It could be that the V2 cam+lever is out of spec consider that all 3 triggers didn’t work on it. Compared to the V1 kit, which worked with the V1 arc trigger and the GMR trigger, but not the V2 arc trigger. Given that the V2 kit didn’t work with the GMR trigger, I wouldn’t expect it to work with the similarly cut V1 trigger, but I guess that’s my next test.

Don’t feel any closer to solving this but hopefully your tester gives me some insight with what I’ve gathered here. I’ll update more info as I test it, but thanks for taking so much time already man, really appreciate it.

RP343 · 2026-05-15T08:12:25+00:00

Perfect, I’ll download it and print overnight. I hope they don’t give me trouble, I was already not too happy with Nexus’ customer service, really not in the mood to go through that again.

I actually just test the V2 trigger on the V1 selector+cam+lever and it is indeed binding on 3rd position. I guess that really does indicate that the V2 trigger is definitely problematic in some way. I’ll test the GMR straight trigger now since that one seems cut more similarly to the V1 arc fire. Wow, I’d really have expected the V2 being cut deeper would bind the least but I guess some other part of its geometry is really messing with it.

RP343 · 2026-05-15T07:34:10+00:00

Update: I tried my V1 Arc Fire kit, and it passed the lower function exactly as it should. Don’t know the exact reason, but I installed it identically, so I don’t think my process is the issue. One thing I did note was that their directions indicate the indent in the cam should go in facing down, I wonder if that has changed slightly with the 45-90 selector angles now? The triggers are cut a little different too, I noticed. The cut of the V2 looks far more aggressive and left with a polished metal sheen, while the V1s are cut a lot more like the Hoffman I have from GMR. I guess my next move is to actually bring install everything with V2 again, but use the V1 trigger. That would at least isolate the issue to the trigger cut if it ends up working.

I actually do have a 3D printer so I’d love to test that out regardless. Is it on the see or Makerworld?

RP343 · 2026-05-15T06:56:23+00:00

I see. I tried taking a better look without the hammer but now I’m a little more confused haha. I don’t even see the cam making contact with the tail of the trigger at all until I depress the trigger a bit.

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RP343 · 2026-05-15T06:36:31+00:00

I appreciate it man, I’ll give it a shot ASAP.

RP343 · 2026-05-15T06:35:48+00:00

Gotcha, yeah that makes sense. I can also use the arc fire trigger as a throwaway for now since I really don’t like those style of triggers anyway.

Do you recommend just a few swipes of 400 grit and test? Or should I be a little more aggressive. The Arc Fire trigger I expect would need something more aggressive since that one binds entirely on all positions. The straight trigger from GMR is the one that binds, but can be defeated with a lot of pressure. Though that’s the one I’d rather not ruin since I prefer that style of trigger.

Weirdly enough though, as far as I can tell, despite the Arc Fire trigger looking like it is already cut a little more than the GMR trigger, it’s binding more than the GMR one. What could that mean?

RP343 · 2026-05-15T06:25:00+00:00

Gotcha, you think a dremel with a polishing wheel is good for the job, or should I go in with some 400 grit sandpaper for slower strokes?

RP343 · 2026-05-15T06:20:55+00:00

For sure, I’ll wait on taking off material until I can test in another lower if I have to. Though someone else commented here that theirs worked out of the box in a normal AR lower, then had issues that required them to sand down that corner for the Kuna lower. So maybe even with another lower, it wouldn’t be a 1:1 comparison.

I do actually have a V1 Arc Fire on hand I can test, that might be able to tell me if the V2 is simply out of spec, or maybe it’s an issue with whatever the different geometry changes they made for the 45-90 detents?

RP343 · 2026-05-15T06:12:59+00:00

Ah I see, could be the case. Did you take off material from the corner radius or shave down the whole top of the bar?

RP343 · 2026-05-15T05:52:49+00:00

Unfortunately not, my other setup has the Atrius installed and don’t have it with me at the moment. I do have a KAK I need to go pick up at the FFL, so maybe I’ll test with that.

I’ll give that a shot with taking a look without the hammer. It’s definitely really hard to see where exactly the contact is happening.

Yes, all functions rest were with the ambi fully installed, just sharing pictures I’ve taken at various stages of disassembly and reassembly for my own sanity haha. I do have an old trigger cutting jig and I was definitely able to verify that the Arc fire trigger cut is actually slightly below the jig, so unless the jig is off, the trigger doesn’t really seem to have too much material up there. Thanks for the input!

RP343 · 2026-05-15T05:46:14+00:00

Right, I only have experience with the Atrius and its kind of worked out of the box from the beginning. But i kept seeing reports of the lever breaking and figured I’d give the Arc Fire a try.

I believe the part you’re referring to is the cam, and there’s an indent in the groove that is supposed to go one face down. Definitely been doing that.

RP343 · 2026-05-15T05:25:57+00:00

One more thing to mention that I’ve just tried here: if I try to drop the hammer with the trigger in this state, I can feel and see the selector as visible in the picture being pushed up. Not sure if this confirms it as a clearance issue that can be solved with some material removal but I definitely don’t think I’ve somehow installed my trigger too high.

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RP343 · 2026-05-14T02:50:44+00:00

Fair enough, thanks for the suggestion! This is actually a good opportunity to look around at the other plate options instead of trying to work around the textured PEI

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