AR 15 lower question

I am new to this forum and this is first post to the AR listings. I have a question concerning "adjustments/fittings". When I have a steel part and it does not fit into the hole in the lower or upper, the part is just too tight! Should I take metal off the aluminum or the steel part? I immediately want to say the steel part. Then repark the part. This way I do not remove the hard anodized skin off the aluminum. But, then I have a receiver that is non standard and a steel part fitted to just this one lower/upper. In every case I have found the aluminum part to be a fault. Olympic lower and various maker components.

I have had to open up the mag release hole and a couple of pin holes. Say I removed maybe .006 to .010.

What is the rule (if any). To be honest I have taken off the aluminum as it is so easy to deal with, a little black felt tip or touch up and all is good. We will never cycle a mag release enough to wear into the aluminum and I figure there is at least .015 of anodize there anyway.

Ask Chuckindenver, he will probably know how deep the anodizing goes. Personally, I have done fitting and I would enlarge the hole to take the pin. I never experienced problems because of it.

Don't remove metal from either! You may have Colt made pin. The standard pin dia., for the hammer & trigger pins is .154". For reasons known only by Colt, they decided to use slightly oversized pins to prevent the installation of M16 full-auto or burst parts from being installed in the lower.

You may have one of those oversize pins and it will be like "putting a square peg in a round hole." Removing metal on either will destroy not only the finish but surface hardening. Get a set of the proper sized pins. Don't force a large pin in a small hole; it will just damage one or both parts.

That's a good point, Kirk. I forgot about those odd sized pins Colt produced. I was thinking standard parts ie military surplus or whatever you would call it.

In the case of the mag release, if at all possible take metal off the steel, not the aluminum. The off spec receivers are usually 6061 are than 7075 and can wear very quickly when the anodizing is removed. 7075 isn't quite as bad to wear, but it really degrades its performance over the long run.

The best solution? get a receiver that's right to begin with. As cheap as they are (bare), why settle for sub-standard?

I agree about using a receiver that is properly sized, my problem is these are purchased and I am stuck with them, only 2.

I did not mean to imply that the pins were wrong size, only the mag release button and magazine catch. Everything else fits well.

In any event, I believe I received good information and will try to conform.

Thanks!