223 Axis mag mod?

Howdy gents,
I am interested in increasing the usable COAL length in the mag so I can seat a 75 gr Amax closer to the lands.
I have a couple of questions...
Can I drill out the rivet at the back of the mag, remove the black plastic block and shave it down a few thousandths and then somehow get another rivet in there and see if it works?
I know if I screw it up I can just get another mag but would rather use that money towards bullets or powder if I can do it right the first time.

Thanks for your time and advice.

Once shaved down, try epoxying it back in instead of a rivet.

That is a good idea on the epoxy.
Will reducing the size of the block cause issues with the spring being able to feed the next round up into proper position?

If your only talking a change of fractions of an inch, I don't think that will cause feed problems. That being said, IF it does, you can always get another follower and trim that to the size of the mag box opening after your modification.