AR-15 pocket too shallow-mill or modify trigger?

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The trigger disconnect is catching the hammer after the first shot in an AR-15. Should the cerakoting by sacrificed by milling out the fire control pocket or should the trigger be modified?

Under the direction of another member here, an 80% lower was milled and the measurements given were faulty. The depth of the fire control pocket is 1.243, spec is 1.249, diff of 0.006". The first trigger (Stag Arms LPK) tried wouldn't rock back enough to allow the disconnect to release without pressing down on the trigger rear shoulder. The second trigger would allow the trigger to pull, but the disconnect engages after the first shot and the trigger won't pull a second time until the bolt is manually cycled.

The rifle won't be modified with a drop-in trigger kit. There are a couple of choices: sacrifice the custom Cerakote color inside and mill to a greater depth, modify the disconnector, or cut a relief in the trigger for the fire selector switch. Which option would you recommend? Obviously the latter two are a much easier option.
 
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If you still have the jig, I would mill out the lower and make it right. Even without the jig, I would try to make the clearance in the lower using a dremel. I wouldn't care about the finish inside the receiver.
 
.006" ?

Are you sure that's enough to cause interference?
Did you confirm the disconneter spring is installed the correct way, it is often installed wrong, but I'm not sure what problem that will cause
 
If you still have the jig, I would mill out the lower and make it right. Even without the jig, I would try to make the clearance in the lower using a dremel. I wouldn't care about the finish inside the receiver.

Jig isn't available, but another could be purchased in the future.

.006" ?

Are you sure that's enough to cause interference?
Did you confirm the disconneter spring is installed the correct way, it is often installed wrong, but I'm not sure what problem that will cause

Another Anderson lower measures 1.255", for a difference of 0.012" between that and this one. Did confirm the spring is installed. The trigger tail has to be pressed down hard to install the selector switch.
 
My prints show 1.249" + 0.010" for depth, so 1.249" would be the minimum. I'd re-cut it. No need for a jig - you don't even need to go all the way to the sides - just the area in the center where the trigger is.
 
I suspect the trigger hole is too low. The 0% lower I did was cut to 1.250 and worked fine. if the trigger hole was too low you would have this issue also. the center of the trigger hole should be around .939 from the top deck of the lower.
(in the ray vin tutorial http://arlower.ray-vin.com/ar15/chapter03.pdf you can see the locations of the holes. ( they index off of the front take down pin, (0.0 is centered from there.) so I added the .250 to the 0.0 to get the number. ) or if you have another lower available compare the locations.
 
I suspect the trigger hole is too low. The 0% lower I did was cut to 1.250 and worked fine. if the trigger hole was too low you would have this issue also. the center of the trigger hole should be around .939 from the top deck of the lower.
(in the ray vin tutorial http://arlower.ray-vin.com/ar15/chapter03.pdf you can see the locations of the holes. ( they index off of the front take down pin, (0.0 is centered from there.) so I added the .250 to the 0.0 to get the number. ) or if you have another lower available compare the locations.

Check both sides .
Table could of been out of square so one side is off .
 
Mill it ! My first build I mucked up the rear pocket on a j Madison lower. It still worked but I filled it with marine tex and milled it again. So it's better to do it right.

Sent from my SM-G900T using Tapatalk
 
Just wondering - is your mill an import? If so, the handwheel dials are only worthwhile for maybe up to 2 inches. Further than that and a tolerance error builds up. Most cheaper import mills use metric feedscrews, and try to adapt to 1/1000" readout handwheels, with the inevitable results.
 
I suspect the trigger hole is too low. The 0% lower I did was cut to 1.250 and worked fine. if the trigger hole was too low you would have this issue also. the center of the trigger hole should be around .939 from the top deck of the lower.
(in the ray vin tutorial http://arlower.ray-vin.com/ar15/chapter03.pdf you can see the locations of the holes. ( they index off of the front take down pin, (0.0 is centered from there.) so I added the .250 to the 0.0 to get the number. ) or if you have another lower available compare the locations.

I did this on my first lower. I just kept touching the bottom surface more and more until the trigger cleared the safety barrel and also worked the hammer properly. Ends up being an amazing milspec trigger due to zero slack at the start of the pull.
 
Are you really worried about marring the Cerakote on the inside of the receiver??? Seriously.

With that said, if you don't have access to machine tools, I might take a file to the bottom rear of the trigger to allow it to rock backwards further, which would allow it to reset. Look at it as an opportunity to have a trigger with little to no pre-travel.

Don

p_100003600_1.jpg
 
I just finished my 80% lower. The trigger pocket measures 1.260. Will this be too deep to work properly? I am new to the area world, and any advice would be a big help.
 
My prints show 1.249" + 0.010" for depth, so 1.249" would be the minimum. I'd re-cut it. No need for a jig - you don't even need to go all the way to the sides - just the area in the center where the trigger is.
I just looked at the blueprint I have... Depth IS listed as 1.249" +/- .010

This is why you test fit the FCG when you're finishing one of these to make sure things are 100% before you call it "done".

For the lower I finished, only one has an issue. The forward corners are not a tight enough radius. So, the Velocity trigger pack I picked up won't fit in it. At some point I'll get in there and correct the issue. But, I have a FCG already in there (that works without issue) so there's zero rush.
LowerFCGdepth.PNG
 
I just looked at the blueprint I have... Depth IS listed as 1.249" +/- .010
Yup - I've since looked over various versions of prints - some show +.010, some +/-0.010 That's why before building anything I try to acquire as many different prints & drawings as I can. Whenever a difference is found, have to sort of wing it.
In a non-critical place like this, I'd always go on the looser side of tolerance if there are any questionable specs.
 
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