Magazine Modification Illegal?

Would the ATF consider it illegal if one was to modify an AR-15 blank magazine to make it fully functional with regular ammunition?

I was in a store the other day looking at some plastic bright orange blank mags, and noticed that the only thing preventing loading a regular cartridge was a small tab at the front lip which would contact the bullet and keep it from being depressed into the mag. It would appear that 30 seconds with a Dremel tool could remove the tab.

Would the ATF consider this an illegal mod to a firearm?

A magazine is not a firearm...so unless you have any local ordinances prohibiting particular sizes, I don't imagine why this would be a problem. Only thing I could see potentially being a problem is the bright orange "hey it's a toy" color, if you were to run afoul of the wrong LEO.

But I'm not a lawyer or representative of the BATFE.

Would it be illegal to swap the follower from your 30 round 5.56 magazine with a follower for a .458 SOCOM, turning it into a 10 round magazine?

No.

So unless, like Mayvik says, there are local laws prohibiting magazine capacity, I don't see any issues with modifying a blank firing magazine, turning it into a regular magazine.

The bright orange color might raise a few eyebrows, but I've seen Lime Green, Bright Blue, Red, and other assorted colors for magazines and other parts of the gun.

I used to have some Pmags in bright orange for what that's worth regarding color. I agree with the previous statements that it is not illegal to modify a magazine, your local laws not withstanding.

What is the purpose of a blank magazine? AR's will not cycle blanks without a BFA (Blank Firing Adapter) and blanks load just fine into a regular magazine?

What am I missing here?

What is the purpose of a blank magazine?
So you know that they contain blanks. They're bright orange, and they won't accept a live round. Beats the heck out of wrapping magazines with blue or red tape.

Oooh. . . Shades of Die Hard 2.

If you are going to be using blanks, I cannot see any reason to have live ammunition anywhere near that evolution. One of my jobs involves the firing of lots of blanks with M4/M16, M249 and M240B weapons. Live ammo of any kind is forbidden anywhere in the active area.

I suppose there are reasons to want live and blank ammunition firing in the same area, I just can't think of any sane ones.

This is nothing more than my opinion.