Reaming holes in lower

[Curley Red]

When putting the lower together with the parts kit does anyone ream out the holes first to get rid of the finish?

[MrPlink]

why would you do that?

[Flintlock Tom]

No, you risk enlarging the holes. The finish won't hurt anything.

[h0use]

you dont need too?

[VytamenC Tactical]

nope no need to just gently tap the pins through.

[Curley Red]

why would you do that?

When you put a finish on a piece of metal the holes will become smaller making for a tighter fit. A lower is not made from black metal, it has a finish on it, therefore the holes are smaller than spec. I really doubt they took into account the thickness of the finish.

Having been in the engineering business for a while I have seen where the finish has made the holes a bit smaller then in raw form and we have had to remove the finish to make parts fit. Of course this was parts for the space shuttle but I figured it would be the same with firearms.

Just wanted to check to see what others are or are not doing.

[Cokebottle]

Some of the parts might be tight.
They will loosen over time.

The "finish" is not paint... it is a layer of oxidation produced by anodizing the aluminum and it is there to protect and harden the surface.
Reaming the holes will remove this thin layer of hard material and result in a lower that will be very sloppy very soon.

[russ69]

...Having been in the engineering business for a while I have seen where the finish has made the holes a bit smaller then in raw form and we have had to remove the finish to make parts fit. Of course this was parts for the space shuttle but I figured it would be the same with firearms....

Well, at my company (LockMart), the hole diameter was after finishing. Pretty much standard in aerospace. On the AR15, the coating is a hard finish and you want it in the holes.

[dfletcher]

I'd like to enlarge the hinge pin hole on my POF lower, I wouldn't have to use their hinge pin and sleeve set up on the DPMS upper. But my assumption is that doing so would remove the "hard coat" anodizing and expose the softer alloy beneath. Is that accurate? If accurate for the relatively little used hinge pin isn't it worse for the trigger and hammer pin holes?

[chillincody]

nope no need to just gently tap the pins through.

this !!! it will remove the finish were needed

[Mr. Meeseeks]

I lightly finger twist correctly sized drill bits through each hole to remove any possible flashing. However, I've never encountered any flashing in the wholes yet.

[Cokebottle]

You should not find any flashing in the holes since they are drilled during the CNC process and not created during the casting/forging process.

[Mr. Meeseeks]

You should not find any flashing in the holes since they are drilled during the CNC process and not created during the casting/forging process.

You know, I stupidly never thought of that. I just routinely finger twist drill bits through most new parts that need assembly, just something I was taught.

[Cokebottle]

I test fit what is supposed to go in first, then ream if needed (not AR lowers, but other items that I've built/fabricated/assembled).

[Mr. Meeseeks]

I'm the same way. I'm can be somewhat of a perfectionist.