I have never been a fan of the pin on muzzle brakes as I have seen 4 of them
fly off during firing. 2 on SKS's and 2 on Mosin Nagant rifles. Only one of
the brakes was found down range the next winter after the grass died down.
No real damage was done to the rifles except some deep scratches on the
outside of the barrels.
Maadi rifles barrels were turned down to one of two diameters .480" or
.512" If the barrel is .512" you can thread it 1/2-28 which is the standard
size for M-16/AR-15 barrels. There are AK-74 type muzzle brakes available
with these size threads and also many other styles of brakes and flash
suppressors.
If the barrel is .480" I would get the muzzle brake of your choice and have
it tack welded on the barrel rather than pinned on.
For info on the Maadi rifles click the link for the "Egyptian Rifles" page
of my web pages at
http://mywebpages.comcast.net/jfreeman246/index.htm