I know nothing about the Blaser so am unaware of fundamental defects. The same kind of accident can happen with regular mauser actions as I unfortunately can attest to. Faulty headspacing may be a problem. The kind of headspace problems that can blow guns up and blow bolts back is excessive headspace. If headspace is excessive, the round will chamber easily--too easy. A "tight" round usually isn't a problem. With excessive head space the cartridge case may stretch to the rupture point, releasing deadly pressures into the chamber. The same kind of problem may occur when a slightly smaller cartridge is fired in a larger rifle. I've seen this twice. Both times a .270 Win round was fired in a 7 rem mag. One rifle, a Browning semi-automatic, was completely blown up.
Interestingly, "hot" handloads rarely blow up guns. At worst, the over-expanded cartridge case may stick in the chamber and the bolt may be impossible to operate. An underloaded cartridge case can be a real problem, however. Ordinarily the cartridge case behind the bullet is nearly full of powder i.e. the powder doesn't move much when the cartridge case is placed in different positions. If the cartridge case is significantly underloaded, however, the powder can move. When the cartridge is placed on the horizontal, as it will be when shooting a rifle, the powder distributes itself along the "bottom" of the cartridge case ["bottom" is that half of the cartridge case closest to the ground]. This leaves an airspace on the "top" of the powder. When the primer fires, the fire flashes over the entire upper surface of the powder, igniting almost all the powder instantaneously. The pressures increase enormously and the cartridge case may explode with very negative results.
I had a serious accident--with head injuries--from a Carcano 6.5 mm rifle. I was doing experiments on the Kennedy assassination and had purchased 5 Carcano rifles of Oswald-type to conduct my experiments. All went well using only one rifle. I probably fired 75 rounds through the rifle without problems. For reasons that escape me now, I decided to try another identical rifle. To complete my experiments, I wanted my bullet to exit the rifle going the same speed that it struck Kennedy's head at [if I can remember rightly] at 157 feet. Therefore, I pulled 5 old Carcano cartridges apart and decided that it might be best if I use new powder rather than the old--maybe 70 year old--powder that was in the original loaded cartridges. Of course, using a reloading manual, I downloaded in such a way that the bullet should leave the muzzle at maybe 1800 fps rather than the 2200 or so that the cartridge is rated at. Probably, although I can no longer remember it, the new powder was more modern and "hotter" than the original powder i.e. it took a smaller volume of powder to produce the same effect. Therefore my 5 reloaded cartridges were very much underloaded in terms of cartridge case volume.
I took the first shot with the 2nd Carcano and the rifle blew up. It was like getting hit in the face with a baseball bat. The stock split and the bolt blew halfway out of the rifle. Hot gas and metal frags were blown back in my face. The only thing that saved my right eye was the scope. It must have been blown back against my orbit protecting my eye from flying shell case and bullet fragments. A piece of metal, likely the primer, destroyed my right maxillary sinus. Anyway, I don't recommend it. There is no doubt the round was underloaded but there is a possibility that the 2nd rifle wasn't headspaced correctly. All of these rifles were very old war surplus and it is quite possible that bolts and rifles were mixed up. My fault.
I purchased a used, lever-action, model 99 Savage Rifle. I was firing store-bought ammo with 150 grain bullets. The rifle isn't terribly accurate but accurate enough for ranch deer shooting.....but....recently I noticed that the fired primers were just a little bit "blown". No other overpressure signs but the primers were pushed back just a little. This is the first time I've ever noticed this using a factory rifle with store-bought factory ammo. The rifle--probably from the day it came from the factory--has too much headspace. I'm presently trying to remedy this potentially dangerous situation but, if I can't fix it, I'll have to hang my beautiful rifle up as a decoration.