Trigger doesn't Reset in SS mode - AR15

AntiAnti2A

I have a problem identical to many I have seen here but I believe the circumstances may be a little different. I have three metal/cut triggers. All three of them work flawlessly in a friend's Double Star Core lower. None will work in my Aero Precision lower.

It works fine in semi-auto. In SS mode, it fires the first round and chambers the next but the trigger doesn't reset. The bolt is forward with hammer dropped (forward). The reset lever is vertical. Both rifles pass function tests identically with and without upper. I have swapped uppers and even tried my AAC 300 BLK upper. Again, it works fine on the Double Star but I get the same results with the Aero.

Holding the lowers side by side I can't see any differences, but I think there must be some subtle difference that is causing this.

I have read through all of undeadchew's posts. It sounds like in most cases it required removing some material, but I have not tried that since all three triggers work in another lower but I'm willing if that is suggested.

undeadchew

AntiAnti2A Thanks for reading all of my posts, this is an interesting issue to be experiencing. The first thing that comes to mind is the height of the safety hole, if you have calipers you can measure how deep the safety cam sits in the pocket. I also run aero lowers with the SS, and the only modification I did was to alleviate bold binding by removing a little bit of material from the lever's surface that contacts the BCG.
For failure to reset I usually suspect an overcut trigger but you say the lever resets when vertical. - The solution to an overcut trigger would be to cut a new one with less material removed than the existing problematic one.

Referencing this diagram I made I actually like my lever to reset a few degrees before or exactly 90. Like where the lever actually is in the picture is where it resets my trigger.

AntiAnti2A

Thank you for the quick response. Below is a pic that shows my reset lever at the point of reset. It seems further forward than your example. However, it appears to be the same for both of my uppers. I'm puzzled by the distance between the reset lever and the hammer in your sample. Is that supposed to represent an AR15?

I also took the measurement that I think you were asking. From the top of the safety cam hole to the top of the upper frame is 0.535" on both uppers. Additionally I used a depth gauge to check the depth of the well. The Double Star is 1.310" (possibly 1.3105"). The Aero is 1.314". I'm hoping four thousandths of an inch isn't the factor here. I wouldn't think we're dealing with that level of precision but would be curious to know the well depth of your Aero if you have a depth gauge. I have another Aero that I will be installing SS. Will also check the depth on that.

I have polished the cuts on my trigger and the sear and will put it back together but don't have a high level of confidence. Thanks for sharing your knowledge.

undeadchew

AntiAnti2A Are you sure this is the right picture? That is not where the lever should be engaging the safety, this picture would imply that you could never pull the trigger in SS mode.

I want to see the position of the lever when you move it to the rear, when doing so do not allow the lever to move back forward in the cam as that won't show me where the lever engages the safety.

My picture is of a ar15 trigger jig, so yes everything is in the same spot as it would be in a lower.

Regarding the depth of the Aero being deeper that isn't the issue.

AntiAnti2A

These two pictures show the rear-most position of the reset lever in the cocked and uncocked position. Did I understand what you are asking correctly?

undeadchew

AntiAnti2A No I do not want to see the rear most position of the lever, I want to see the exact position of the lever when it pushes the trigger forward against your finger for a "reset". For example in my picture on the top that is where the lever engages the safety pushing my finger forward on the trigger.

AntiAnti2A

My apology for the confusion. I believe I understand now. Here's how I came to the position shown in the picture.

Cocked the hammer and pulled the trigger, keeping rearward pressure on the trigger.
Cocked the hammer again then moved the reset lever forward until I heard a click and felt forward pressure on the trigger.

undeadchew

AntiAnti2A Okay thanks for the new picture, that part looks to be in spec, mine in the picture does reset a few more degrees forward. Which indicates my trigger in that example has less material removed on the curved part.

So when you slap an upper on and function test, does it reset the trigger?

AntiAnti2A

Yesir, the function test passes with the upper in place. As you pointed out, your picture shows the reset position a few degrees forward of mine. If I wanted to replicate that I would need to recut another trigger and leave a little more material on the rounded part? Is that correct? Do you think it worthwhile?

undeadchew

AntiAnti2A Yes that's right, and I do think it's worthwhile, and I always recommend that people cut their own triggers, I follow a process where I do a few passes on a file, do a function test, repeat if it does not reset, and once it works I stop and polish it up.

AntiAnti2A

Would a dremel with a cutting wheel be sufficient to cut a new trigger or am I going to make a mess? Thank you for all your guidance. If I ever get this nailed down I'll report back to this thread.

undeadchew

AntiAnti2A Dremmel for the right side, but I personally wouldn't use a dremmel for the rounded corner. It's not a race, that's how you end up with an overcut trigger and back where you started in the first place.

AntiAnti2A

undeadchew I cut a new trigger then gradually rounded with a file. At first, I couldn't even pull the trigger in SS mode. After a few iterations, I was able to pull the trigger and get a good function test. I took it out and live tested. It spit out two rounds, chambered a third but did not reset. This is progress but I'm not sure how to proceed. Should I take a little more material off the rounded edge or something else? As you can see in this latest pic, the reset is a few degrees further forward than it was with the other triggers
.

AntiAnti2A

Thank you again. Yes, the rounded corner would best be done with a file in small increments.

undeadchew

AntiAnti2A After the third, did you open the action to see if the hammer had already fallen? If the hammer had fallen the trigger did reset.

Also to answer your question no I would not round the trigger more at this point.

Next question would be do you have any spacers (quarters) in the back of your buffertube? This is something that is recommended on reddit to alleviate bolt bind.

AntiAnti2A

undeadchew The bolt was full forward so I would have to believe the hammer had fallen. I'll run a live test again to confirm. I do not have spacers in the back of the buffer tube. I was under the impression that wasn't necessary with an H3 buffer spring but I'll try that too and report back.

You're help is amazing. Thank you for sticking with me on this.

undeadchew

AntiAnti2A Sorry for the confusion I don't recommend spacers that would reduce the travel of the bolt!
People who recommend that on reddit suggest that without understanding what the proper solution for bolt bind is.

I am just trying to find out what could be causing your issues.

What barrel length are you using, have you tried a standard carbine buffer weight? an H3 could be inducing bolt bounce. People on reddit also suggest using an H3 as a solution to bolt bind which is also wrong.
ar15.com/boltbounce

Bolt bounce is when your bolt bounces backwards after closing, while at the same time the hammer could be falling and would cause a light strike out of battery, meaning the round doesn't go off.

Most of what the super safety reddit suggests is just flat out wrong hacks that is circulated in an echo chamber, quarters in the back of the buffertube, grinding upper receivers, H3 buffers.

If you experience bolt bind after switching from H3 to H1 (standard carbine) I suggest filing the surface of the lever which contacts the BCG, this is NOT REQUIRED, only if you are experiencing bolt bind when charging the bolt to the rear.