DD M4A1 upper with a can?

[300winmag]

I recently acquired a DD M4A1 upper and am considering having the original muzzle device removed, and an AAC can mount/flash hider pinned and welded in its place. It is longer than the stock piece by a hair, so NFA will be happy.
My questions are as follows;
Without an AGB will I be able to run reliably?
If not, can I compensate with a new buffer & spring and if so, which combo?

The can is an Advanced Armament SR-5.

Thanks

[MistWolf]

Look into the BRT EZ Tune gas tube- http://blackrivertactical.com/WP/Adj...Drive-c6464009

Clint, a regular member of the forum can help you