9mm mag blocks

What is the difference in the following?

http://www.brownells.com/.aspx/sid=5...nversion_Block

http://www.brownells.com/.aspx/sid=4...nversion_Block

http://www.brownells.com/.aspx/pid=1…_BLOCK_ADAPTER

And the Rock River mag blocks.

I would like something I can swap out at the range, is reliable…if possible.

Check out the one from Spikes…they were on sale last time I checked.

http://www.spikestactical.com/z/index.php?main_page=product_info&cPath=68_71&products_id=188
Do you have one?
How is it different than the others?

I went with the bottom loading Hahn. Took my gun out for the first time today and it ran great. The Hahn bottom loading and dedicated both lock the bolt open after the last shot, the top loading does not.

I have a dedicated Hahn Block that I like very much which I use in my Dedicated SBR, for my FA M16 I use a top loading Hahn block. Ignore the ProMags, their junk. :mad: