So I just installed a MBT in my AR, but am running into issues. I first installed with the heavy spring, but it felt really heavy, like far heavier than I imagine it is supposed to. It also felt gritty. I uninstalled it, greased it, and reinstalled it several times, but kept running into the same issue. Eventually I decided to try the light spring, which feels much better and closer to what I imagine it should be like. However, there still seems to be some grit/resistance during the first stage. Interestingly, I didn’t notice it yesterday when I first installed it and though the trigger felt great, but today it feels heavier and grittier.
Another issue is that the trigger does not want to reset on its own, and also is sticking. What I mean is that when I pull through the first stage and approach the wall of the second stage and then let off the trigger, the trigger will stay stuck in that position and will not reset to neutral without me having to push it forward. Then when I try to test the reset, the trigger will stay stuck fully depressed, and will not reset unless I push it forward.
I’ve uninstalled and reinstalled this thing probably 5 times now (around 4 were with the heavy spring, then the last was the light spring) and keep running into issues. I feel like I am installing it correctly, is there something I am missing? What could be causing this?
Hard to say. Has this lower been used previously and worked properly with another trigger? Have you watched any of the YouTube videos to check your spring orientation, etc? Can you get us any pics so we might spot something?
Here are a couple pics of the trigger installed in the lower, hopefully that helps. Please let me know if there is anything else needed to diagnose the issue!
I have three MBT-2S triggers, two with light and one with heavy spring. All of them have smooth take-up and no grittiness at all. Something is wrong with yours or it is interfering with the receiver somehow. You could try cleaning it with a blast of brake cleaner and relubing the entire thing, but it should not have grittiness regardless of what you think the pull weight should feel like. Also check if the trigger shoe is rubbing against the receiver in the trigger slot area.
What safety are you using? From what I can see it looks like mil spec, which should be fine, but I did have a similar problem with an MBT and BAD-CASS short throw. I had read that there was some grinding and polishing I could do to get them to work together, but in the end, I just ended up installing a Colt ambi safety and everything with the trigger started working properly. Do you have another safety you can try? I have some extras I could help you out with if you don’t, just pm me.
I honestly can’t see any difference between yours and mine. I think a call or email to LaRue is in order. Do you have another lower you could install it in? Just to check. Here are pics of mine. Difficult to do with a phone. Yes I know the rifle is dirty.
It doesn’t seem to be rubbing. It it possible the trigger is misaligned? The trigger pin went in pretty easy, and this has happened each time I’ve reinstalled it
I am using a milspec selector, and this is the only one I have. I don’t think it’s contacting the safety? Thank you for your offer, I will let you know if that turns out to be the problem. This is also my only lower, just built the gun, so unfortunately I don’t have another one I can try
There is no disconnect to check. It’s pre-assembled from LaRue.
Probably a trick of lighting. One of my pics I didn’t post is the same way. That part looks beveled in his picture, but it’s actually radiused off.
There really isn’t any way to get it misaligned, the pin goes in or it doesn’t. Your selector looks like it has plenty of clearance, but you can’t see the piece where the tail of the trigger is under it. As mentioned above, make sure the trigger bow itself isn’t dragging on the opening in the bottom of the lower, mine is VERY close to rubbing.
The “feel” of this trigger should be about 2lbs of takeup for a quarter inch or so with no grittiness at all, then a fairly clean 4# break. If there is grittiness in the first stage, look really close for rubbing in the trigger opening at the bottom of the lower.
At that point the only source of “grittiness” is within the trigger itself and that’s a LaRue problem.
If it is rubbing where the trigger drops in, what would my options be? I got a glimpse of how it should feel when I first installed the light trigger spring, and I loved it. It seemed good at first (I think) but then went back to heavier and grittier.
It’s captured, there’s no reason for them to used the tapered style disconecter spring on this trigger. I guess they could of, but I doubt it. Also, it uses a rivet type pin to assemble the trigger and disconnecter, so not easy to disassemble.
You can file the hole a little larger in the bottom of the lower, or file away on the trigger. If it’s rubbing, I’d modify the lower, but that’s just me. Many will say just send the trigger back.
So I disassembled it again, this time greasing the trigger hole in the lower and the sides of the trigger, and it feels much better. There’s still a little grit in the first stage, but it resets normally now and the pull weight feels more like what I would expect, although maybe still a little heavy and it feels like it might be getting heavier as I try to work it in. Sounds like maybe the trigger hole in the lower might be scraping the trigger? I will probably try filing it a bit, but I can’t tell exactly where it’s making contact. This might be a temporary fix, but it would be a pain to have to keep regreasing it there every time.
No issues like that with mine. You might just be able to polish the edges of the opening with one of those emory boards for finger nails. The fact it loosens up with grease means it’s really close to being o.k.
Seriously, it’s bound to happen to someone as it’s a man made item. Things go wrong, and that isn’t a negative reflection on the company. If you call and get insulted, mocked, and or called names, that is a negative reflection of the company. It’s just a trigger, they will make it right.
