A while back, someone posted the dimensions necessary for blocks used to make 20 and 30 round magazines legal under New Jersey's 15 round limit.  Since the archive search doesn't appear to be working, I can no longer find it.  Does anybody have this info?

I can't help you with the 20 round mags, but I have cut several blocks for my 30 round mags for when I make my trips up to occupied territory. I just use a piece of wood that will fit into the center of the spring. I cut mine to 2 3/4" long. My best advice is to try that as a starting length and test it out, adjust as necessary.

I remember seeing a post with a link to a letter or opinion from either the state AG or  the head of the Sturmabteilung (State Oink) indicating that a temporary block was not acceptable and that the mags must be incapable of being reworked to accomodate  more than 15 rounds. Now this being Jersey the whole issue is pretty much laughed at, but you might want to research the issue before  any such mags see the light of day in front of some eager beaver PAMF LEO looking to play hard ass.

See [url=http://www.ar15.com/forums/topic.html?b=1&f=6&t=157749]Here[/url]

Thanks for the info guys.  As for whether temporary blocks are ok, there has been no progress on the state police proposed regulation that would make it officially illegal.  They're reg proposal said they've always taken the position that temporary wasn't allowed, but then they stopped the proposal before setting it in stone.  Doesn't mean they won't break balls, but they would appear to have a tougher case now against anyone who stands their ground.

In the meantime, I was able to dig up the dimensions I was asking about on an old piece of scrap paper.  Answered my own question.  In case anyone from, or going to, NJ is interested, the measurements are:

20 Round:  1" x 1 7/8" x 7/16"
30 Round:  2 3/4" x 1 7/8" x 7/16"

The block squeezes snugly between the spring and the floorplate.

I've been out to Jersey and the politicians have ruined the place (I'll never be back if I can help it)  I got off the plane and went took a cab to a rental car place and was hit with a $10 visitor tax on my rental car.  

Then they taxed the shit out of me for every historical site I went to see (even though as Americans they should be encouraging us to visit the birthplace of the nation).

if they want to tax us because were visiting, fine I'm not going back.  (here in Wisconsin we don't tax you for anything extra for visiting).
Also it's impossible to get anywhere fast because you always have stupid liberals walking in front of your car (even though the light says don't walk). You're welcome to come to WI but if you try that don't walk/walking bit (we'll run you over and rid the world of your liberal stupidity).

and unrelated but similarly they have government run parking garages in nearby Boston with the lowest rates in town- $30 a day! in Milwaukee it costs $7-$10 a day to park.
Then I went to Paul Revere's house and was charged $5 to walk through the 4 bedroom shack (it took 5 minutes)