Another AR trigger reset problem

[cheezedawg]

Hi all-

I've lurked for a while, finally registered. Great forum!

I'm new to ARs, and I jumped in with both feet on an 80% lower build. I completed the lower and was working on the build yesterday, but the trigger isn't working quite right so my progress has stalled. When I pull the trigger, the hammer goes forward, and when I push it back it engages with the disconnect. But when I release the trigger, it doesn't release from the disconnect and reset to engage with the sear. I've triple checked the spring alignments for the trigger, hammer, and disconnector springs, and I think they are right.

I found that if I put a little bit of pressure on the back of the trigger to push it forward, it does reset then. So I am thinking that maybe I didn't mill out the lower quite enough. It looks to me like this is restricting how much the trigger can move forward just a tiny bit, but enough that it can't disengage from the disconnect. Does this seem plausible? I was pretty careful milling and thought I went deep enough, but maybe not.

Or is there something else I should be trying?

In the meantime, I decided to take it apart in case I need to get it back into the jig, but I bent 2 punches trying to get that darn bolt catch roll pin out, so I just ordered a bolt catch punch set from Amazon.

Thanks!

[shafferds]

How deep is your fire control pocket? My guess is its not deep enough causing the issue your having. Check your measuements. If I recall should be a depth of 1.249 + 10 thousands for margin of error. I've set them at 1.250 and been fine.

[SkyHawk]

And make triple sure the disconnector spring is not upside down. And also check the trigger SLOT to make sure the trigger has enough room to move. Usually if the pocket is not deep enough, you can't get the safety in.

One way to check if your pocket is deep enough is to see if you have a little play in the trigger with the safety ON. With the hammer cocked and safety on, the trigger should not be bound tight, it should have just a little movement.

And you probably figured it out by now, but there is no reason to assemble anything except the trigger group and verify function thoroughly before you go putting in pivot and takedown pin, trigger guard, bolt catch etc, because there is a chance it has to go back in the jig.

[BajaJames83]

tagged for later.

[cheezedawg]

With the safety on, there is hardly any play in the trigger- it pretty much does not move. Whats the best way to measure the depth of the pocket? And how much trigger movement is normal? Even with the safety set to FIRE and the hammer cocked, the trigger doesn't travel very far when I pull it (but enough to release the hammer).

That said, I am starting to doubt my theory. When it is engaged on the disconnect and I push the the trigger forward, I do see the trigger move forward a little when it clicks as the disconnect disengages and it hits the sear again.

[SkyHawk]

The best way to measure pocket depth is with the depth gauge on your calipers. You can also mark a dowel at 1.249" and then use it to measure the pocket depth.

Another problem you may have is trigger/hammer pin holes or safety hole are not located correctly. No easy way to fix that.

[67Cuda]

When I did my 80% 308, it had a trigger issue.

Solution was to buy a CMC drop in and move on.

Never regretted doing that.

[cheezedawg]

I dont have calipers, so I measured with a dowel and it was right at 1.25" (without calipers, I don't think I had the accuracy to distinguish a .001" difference).

I decided to put a few drops of Hoppe's oil on the disconnector, and it started working maybe 10-20% of the time. So I got out some Grizzly Grease and worked that in on both sides of the disconnector, and it got even better. I'm not sure it is working 100% of the time now, but its pretty close (I did over 30 in a row without any failures).

I might call that good for now until down the road when I buy something like a CMC drop in (thanks for the pointer).

[ar15barrels]

Whats the best way to measure the depth of the pocket?

The best way to measure pocket depth is with the depth gauge on your calipers.

False.
The best way to measure depth is with a depth micrometer.
The depth rod on calipers will work though if someone does not have a proper depth micrometer.

[ar15barrels]

I dont have calipers, so I measured with a dowel and it was right at 1.25" (without calipers, I don't think I had the accuracy to distinguish a .001" difference).

You are not properly equipped to be finishing 80% receivers if you do not have a dial caliper.

[mattkeef]

I had that before

So I had the same problem and it was the disconnector spring was upside down.
After disassembling and reassembling the trigger 3 times, I came to find I had installed it wrong all 3 times!
So I suggest going back and taking your times reassembling.

[xsefan]

I have seen BCM disconnectors with this problem In 80%lowers. 400 grit to the contact area . 3 or 4 swipes max.
Most likely you hammer pin hole is too high for the trigger pin. Don't use that jig any more