Neat AR-15 Modification

[skeeljc]

If you happen to have an Aero Precision AR-15 lower receiver (maybe others) there is a 1/4-28 threaded hole that is directly in line with the rear takedown pin boss in the upper receiver. Aero Precision includes a 1/2" long allen set screw with a polymer tip. The set screw pushes up against the upper and removes any play between the two receivers.

I discovered that McMaster Carr has spring loaded 1/4-28 set screws. They are 1" long but they will fit. Just search for "Hex-Drive Long-Nose Spring Plungers" on the McMaster Carr website. They are available in 1# to 3# force and 3# to 13# force. I used the 3# to 13# range and screwed it in until it bottomed and backed it off a half turn. The spring plunger allows you to open the takedown pin without loosening the screw. This is a much better solution than an Accu Wedge.

When I used the AP polymer tipped screw I had two issues. First you need to loosen the screw to open the rear takedown pin. Second the polymer tip will creep over time and the preload will be lost.

 

[Mark M.]

Excellent, thanks

 

[jkohler]

Nice find

 

[Sieg]

Nice find.

I'm glad I don't have to do inventory at McMaster Carr, is there anything they don't have?

 

[skeeljc]

They also have a SS body with a SS plunger that has a 15# max force.

 

[T-shooter]

I've used the Accu-Wedge insert. They are a pain and have to be tight to work making it necessary to use a tool to press out the rear pin and they tend to loose a little tension after time.