I just bought a 9mm beta mag, for my olympic arms 9mm upper, the upper came with a mag block for sten mags, so I had to get another mag block, I got one from adco. My question is the mag block has an inverted J piece on the top of it, this won't allow the upper to close on the lower, should I dremel this inverted J off? I can't see any need for it.  also there is a pin with a spring around it on the upper that hits the inverted J, dont really see what it's use is either.  I don't have much experience with 9mm ars, I got the upper and beta, for run and gun at the range ( cheap mp5 haha) any help would be greatly appreciated. Thanks Treeman

hello the pin with spring on it is what the empty shells hit to kick them out  the mag block with the j on top is for the colt setup from my understanding which the uppers dont have the pin with the spring on it my thoughts are you should be able to cut off the j on the magblock i have thought about doing that to run a beta in my oly arms upper but havent got around to trying it maybe someone else can help if they know if it works or doenst if you try it let me know if it works or doesnt.

Thank you for the reply, I also posted on the trouble shooting forum, and got  a lesson on using my old mag block, go figure, I guess I didn't word it write, I thought I was clear that my problem is the same as yours, if you hear anything don't forget me either.Thanks Treeman                                        I think I got it, the inverted j is the ejector for colt type 9mm, since I don't have a colt, I am going to whack that mother off tomorrow, if it fails I will tell you, if it works I will tell you, but either way I"M WHACKING MY BLOCK OFF TOMORROW!,   all you gutter minds please disregaurd the above statement!