My m70 has this pesky bolt that runs through the gas block. It holds the grenade launcher sights in place. The nut that secures the bolt in place always comes loose after about 20 rounds of shooting and eventually causes the weapon to jam. I've looked into putting a standard yugo gas block on it but from what ive read, it can be a bugger. Is there a way to get that nut to tighten down so it wont come undone? I was thinking about finding a washer of some kind to lock it down.