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Posted

I don't know if this forum is for extreme beginners with Polymer 80 .308 80% lowers but here goes:

I finished the lower and installed the trigger group and mag release that those parts seem to work well. But when installing the bolt catch release (bcr), all went to hell. It was part of Aero Precision's LPK. I thought I had researched things well but didn't really look at the bcr. The LPK had a roll pin for the release and I (without thinking) used it not noticing it was a blind pin hole. So now, the bcr doesn't work. I have to manually move it up and down, it's too tight for the spring to function.

I have searched and found out there probably should be a 1/16" set screw type pin that goes into the hole. And to my embarrassment, I noticed the threads in the hole before inserting the roll pin but I thought the LPK people knew what they were doing.

Now the problem is to get that roll pin out which I think is just about impossible without destroying the lower. But it's useless as is if I can't get it out.

Is there any hope? Do I just buy another?

I gather some people don't like the 80% lowers but I'm retired and like doing these kind of things to stay busy. Six years ago I did an AR-15 aluminum 80% lower from 80% Arms and it was definitely easier.

Thanks for any advice.

Phil

Posted
3 hours ago, Harveyshot said:

I think is just about impossible without destroying the lower.

Break/cut the bolt catch, just have to fiddle with or maybe cut the pin. I bet a threaded pin will still work if careful. Now you can better fit the next one :thumbup:

Posted (edited)

I'd hope not to ruin an entire lower over such a small problem. First thing I would try is a lot of oil and see if you can work in the bolt catch, and make it move more freely. My polymer 80s have been a little tight (though I've not tried a 308 polymer 80; that scares me a bit). 

Assuming that does not work. My next move would be to drill out the front side, so it's no longer a blind pin hole. Punch the pin all the way through and out the other side (the freshly drilled hole). It's likely that the threaded type pin will still work afterwards assuming the threads didn't get mangled in the process. Obviously might be good to take a file to the inside of the channel for the bolt catch, and make sure it moves freely before installing the new pin. 

But yeah; you could also try to destroy just the bolt catch. That seem a bit more difficult; but maybe I'm not thinking of something that would make it easy. It's certainly a better option than buying another lower.

Edited by Lane
Posted
18 minutes ago, Lane said:

but maybe I'm not thinking of something that would make it easy.

MIM parts seem to be brittle, cut a slot over the pin at an angle with a Dremel and twist it open, guaranteed to leave a mark you can tell your friends about. :thumbup:

Posted

A drop of jb weld on a paperclip. Insert in the roll pin and let it set up overnight. You should be able to pull the roll pin out. You can still drill out the blind side and drive it out if that doesn't work.

Posted

If you're going to leave a mark; I'm not sure that's the one I'd want. 

Still have to get the old pin out even if the bolt catch is off. 

In terms of leaving a mark. I bought a blemished polymer80 that had a defect that was visible in the finished product. I found JB Weld plastic bonder filled the void neatly, and I was even able to dye it the correct color when I was finished. I can't even find the seam after the fact. So assuming you don't do structural damage, you can alway fill in small imperfections. 

Posted

Thanks everyone for all the input. I think I'll try the JB Weld suggestion and if that fails, I'll use the Dremel and try to cut the bolt catch out.

As you can see, there is no way to drill out the blind side of the hole without a lot of damage. At least I'll know what to look for if I buy another one.

Thanks again. I'll report back on the results.

bolt-catch-hole.JPG

Posted

Worst case....a bolt catch isn't essential to a functional rifle. It's not even super important. I'd just spend a while rocking it while you are watching TV or whatever and see if you can get it to wear in and loosen up. 

Posted

Hmmm, never considered the necessity of the bolt catch. It is helpful, though.

As for the rocking, the bcr doesn’t seem to have the same range of motion that the one on my ar-15 has. The 308 barely moves.

Posted
10 hours ago, Harveyshot said:

 

As for the rocking, the bcr doesn’t seem to have the same range of motion that the one on my ar-15 has. The 308 barely moves.

You probably need to modify it, and knock the corner off it with a dremel.

Posted

Update: the JB Weld trick did it! I was sure it wouldn't work because simple little fixes like this usually don't work for me.

Thanks again, Shooterrex and thanks to all that replied.

Time to get the right part and try again.

 

bolt-catch-pin-01.JPG

bolt-catch-pin.JPG

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