Maybe Doing Research isn't Always Good

[jmoore]

Long story short " either too much pressure or not enough. Ammo is ammo. Gotta figure out what the design specs called for and go with that.

"Bursts" as in "full automatic uncontrolled bursts", not Kaboom! (But it's not too far behind, in this case- if the breech isn't locked it makes a mess.)

Ammo ain't ammo. If the primers are too soft as might be found on some commercially produced ammunition, then the impact of a non-spring retracted firing pin during bolt closure amy result in trigger free multiple round discharge.

If you reload, there are primers made just for such weapons, such as the CCI "milspec" primers.

Alternatively, there should be some info as to which ammo to avoid. French surplus ammo may still be had if you shop via internet.

For instance:

http://www.fivesevenammo.com/shop/page4.html