Lapping an AR receiver

[John_Dennis]

I was watching a video on lapping an AR receiver and bedding the barrel. I have both an AR 10 and AR 15 receiver that I want to do this to.

Is there anything special about this lapping tool? Since I am only doing my personal guns, it seems like I could just make a couple out of mild steel and resurface them if they wear.

Thanks
-John

 

[Ulma Doctor]

lapping tools are generally made from softer materials like brass, bronze ,copper ,& aluminum.
a steel lap may work, but the lapping material grains will not embed as readily and lapping could take longer or inflict unwanted wear on a soft part

 

[pontiac428]

Are the accuracy gains as explained in the video from lapping the receiver face, or from gluing the barrel into the upper?

 

[John_Dennis]

Are the accuracy gains as explained in the video from lapping the receiver face, or from gluing the barrel into the upper?

both, the goal is for the barrel to be evenly compressed and parallel to the picatinny rail and not creep due to the stresses of heating and cooling and the shock of firing. In the receiver he is demonstrating, there is an exceptionally poor fit between the barrell and the receiver diameters

 

[Nogoingback]

It would be interesting to know what brand of receiver he uses. A better quality receiver might solve some
of his problems.

 

[pontiac428]

It makes sense to lap-to-fit, and the AR does not have much meat on the barrel extension to align the upper and barrel. It just seems like a step that can be skipped if step 2 is to bond the two parts together with space program adhesive. During the bedding step, the Loctite 620 will also bed any irregularities at the face of the upper, so you could skip the lapping step and go straight for the glue and the torque wrench.

Then again, why on earth am I compelled to nitpick accuracy mods on a semi-auto carbine? It's like giving Formula 1 treatment to a Ford Taurus.

 

[Cooter Brown]

Dont use loctite on an ar barrel... lol it breaks around 200-300 degrees F..... Instead stick some shim stock in the gap so the barrel has to almost be pressed in.....

 

[COMachinist]

Dont use loctite on an ar barrel... lol it breaks around 200-300 degrees F..... Instead stick some shim stock in the gap so the barrel has to almost be pressed in.....

I agree, when that loctite get’s baked a few times. I Would not like to have to change that barrel. It will need heat to loosen it up and it will be hot . Other than that, it is a good idea to have the face of the receiver square, and true. Better yet a better quality receiver is what I would go with.
CH