Best way to alter a +2 12g magazine extender to +1

[grimblyd]

So I've got a 4 * 3" magazine on a semi auto shotgun that I am buying a +2 extension for.

I'm planning on the total magazine capacity length to be ~16.5-17" so that it will ONLY hold 5 3" but that gives me 6 2.75", which I am told is perfectly legal.

What would be a good way to do this? 1" thick piece of dowling in the end? Or does it have to be a permanent alteration that can't ever be removed? Like fill it with solder or something?

Thanks in advance for your suggestions or input!

Dan

 

[lpel]

I used JB Weld to hold a 1/2" wooden dowel in place to hold just a bit less than the max 5 3" shells. I think the alteration has to be permanent. Not something you can easily remove.