80 Percent Builder Forum

80% Lower Forums => 80% Lower Builds => Topic started by: Elko on April 26, 2016, 03:05:03 PM

Title: Question about milling 80% lower
Post by: Elko on April 26, 2016, 03:05:03 PM
I need to know if is it really necessary to mill out the additional area between the safety selector and rear take down pin.
In the attached photo, my 80% lower is on the left and the area I'm asking about has an "X" on it. The lower on the right
is a factory one.
I have not fired it yet but it cycles snap cap  rounds just fine the way it is.
Thanks to anyone who can advise me on this.
Title: Re: Question about milling 80% lower
Post by: Jefe on April 26, 2016, 03:14:52 PM
Welcome to the forum! It's fine not being milled out. It doesn't serve any purpose in a standard AR-15 configuration.
Title: Re: Question about milling 80% lower
Post by: helidude350 on April 29, 2016, 08:52:36 AM
Mostly it is not necessary..........
But............................

If your lower part kit functions and clears, and the upper pins ( or un-pins) to the lower without a fight you are good to go.

Leaving the little bridge can show that your firearm cannot hold an auto sear, lightning link, or drop in auto sear.

All lowers ( even "80 percent) and uppers aren't created the same.

Some may bind at the take down lug. I have run across that a few times.

If you want to swap uppers later, you may find that there is an issue. If you still have the jig, no worries just clean out what you need.

Different fire control parts may not work either. I had Alexander parts that would not fit in a finished 80% lower, but another brand did. ( nothing wrong with the Alexander parts, I used them in something else).

If you use drop in trigger groups, or some full auto fire control parts you may have an issue as the both take up more space. These I have no hands on experience with, except for displays at the gunshop.

So if your parts are happy, and you are happy the extra aluminum is not a problem.
Title: Re: Question about milling 80% lower
Post by: Jefe on April 29, 2016, 12:35:33 PM
Some may bind at the take down lug. I have run across that a few times.

But that wouldn't be related to the uncut "bridge" would it? I have had lugs binds on the long side but they shouldn't on the front/back ends. For binding sides I use a file on the upper lugs until I get a "custom fit"  ;D