P-40 Mag extension on a P-11

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My opinion on this mod has changed!! I saw the way the law is worded and see now that doing this in the way shown on this page will get you in trouble!! The law says any mag that can easily be converted to hold more than 10 rounds is illegal. All you would have to do is take out the spacers and it would be converted, it is my opinion that this could get you into trouble. Actually it is my opinion now that the law is worded too loosely because it is easy to put a p-40 extension on a p-11 mag to make it illegal, which means that any p-11 mag is easily converted to a hi cap and there fore illegal!!

links to the laws ATF site and here

quote from the ATF site :
18 U.S.C. Chapter 44
921(a)(31) The term 'large capacity ammunition feeding device' -

(A) means a magazine, belt, drum, feed strip, or similar device manufactures after the date of enactment of the Violent Crime Control and Law Enforcement Act of 1994 that has a capacity of, or that can be readily restored or converted to accept, more than 10 rounds of ammunition: but

(B) does not include an attached tubular device designed to accept, and capable of operating only with .22 caliber rimfire ammunition.

pay special attention to the part "or that can be readily restored or converted to accept, more than 10 rounds."

I will probably modify the instructions to show how to make the mod more permanant so it will satisfy the law, but as of now I am just using pre-ban 12 round mags that come out to about the same length with 2 legal extra rounds...

I liked the feel of the p-40 mag extension better than the p-11 one, and the bottom tip of it does not stick out as much, but you can not just put a P-40 mag extension on a P-11 mag (you physically can, but not legally), because that would make the new (post-ban) mag hold over 10 rounds. So to remain legal you must limit the mag to 10 rounds. I did so by making 2 spacers out of a piece of aluminum from Home Depot.

I started with a piece that was 1/8" by 1 1/2" by 36". I cut a narrow strip off that would just fit inside the width of the extension. Then I rounded the edges so it would slide all the way forward in the extension, then cut off the back so it fit all the way inside the extension:

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when making the spacers make sure that they are about an 1/8" short of touching the lip of the rear of the new base plate, that gap is where the rear of the mag will go. Notice the gap in this pic:

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This is how it will go together in the mag (notice how the lip of the new base plate goes behind the rear of the mag, not inside it, but the spacers go totaly inside):

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Now the bottom of the spring is right where it was and the capacity is still only 10.

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