In all likelihood, your firing pin spring was not engineered for the thick hard primer cups of military ammo.
There's nothing wrong with either your rifle or the ammo. They just aren't a match. If you wish to take advantage of the low cost Tulammo for practice, a slightly heavier spring would solve the problem.
Another option is to try Wolf, Silver Bear etc. they might work fine in your weapon.
And from my experience with a great quantity of steel cases ammo, I must respectfully disagree with the post about steel case breaking extractors.
I've used a ton of it in several different weapos with no ill effects.
History fails to record a single precedent in which nations subject to moral decay have not passed into political and economic decline. There has been either a spiritual awakening to overcome the moral lapse, or a progressive deterioration leading to ultimate national disaster.
If you think a strong military is expensive, think about what a weak one would cost