I would guess bad metallurgy...
On the reports of "bad Bulgarian". Not the metallurgy of the firearm, but of the brass. The '50's vintage Bulgarian brass seems to be very brittle, and will split at the neck (and sometimes quite a ways down the case as well...) upon firing. This is the case with just about every round of Bulg x25 (at least in the lot we are talking about, most of the '53 and '55 also split, but not as many as the '52) I have fired, the one that doesn't split is usually the odd man out. I have also seen Bulg 54R do the same thing, and have seen the reports of that confirmed on these boards by other members as well. As a matter of fact, you don't even need to fire it to get it to split, as I have slpit some of the brass by simply using an impact puller to pull the bullets! Others have reported having loose bullets and powder in their 54R cans when they open them, which implies the very smae thing, neck splits in the brass in the sealed can. I HAVE NOT however ever seen one split all the way to the case head, nor blow out primers. And the 52 being the tank that it is, if everything is in very good operating condition, you should have no problems.
The other determining factor here I believe is the primers. When I first heard of this, I was already well into my first can of "bad Bulgarian", and since then, I have shot at least one full case of this ammo through my most used 52 with no ill effect. But, I did decide to do a few tests of my own to decide whether I should pull it all down for projectiles, or fire it. This is how I found out (to my satisfaction) about the brittle brass. Also during those tests, I found that the primers are VERY inconsistant, some go off like a magnum, and some go off like a regular SP primer. This was determined by firing the empty brass in a darkened room and measuring the flame and audible pop of several pulled down cases. I think that this also contributes to the brittle brass problem by changing the burn rate, and possibly changing the pressure as well. The charge weights and bullet diameters seem to be about as consistant as Com-Bloc military surplus from the '50's is, so it is not a powder/bullet issue.
I regularly shoot my most used 52 (twice refurbished at the arsenal) with "bad Bulagrian", (I still have about a half a can left...) hot handloads, Czech "subgun" (see below) ammo, (garbage, only good for projectiles and fertilizer) and all other manner of surplus and commercial ammunition without ANY problems, because I keep my pistol in EXCELLENT operating condition by replacing springs and rollers and parts that wear. Taking a note from the Czechs themselves, I have an Armorer's kit, and in it is enough spare parts to keep ten pistols operating. There is only ONE barrel, but there are TEN sets of rollers, and TEN recoil springs. This signifies to me that these are parts that are prone to wear, and are in need of replacement often to maintain safe shooting conditions.
Again, I DO NOT ADVOCATE THAT ANYBODY TAKE ANY RISK THAT THEY ARE NOT WILLING TO ACCEPT THE CONSEQUENCES OF!!
A very good friend of mine who has the tendency to "hotrod" ammunition, did indeed blow up his 52 one day, and I saw the results after the range session. The barrel was cracked at the chamber along one side (not the thin spot at the bottom that is a known weakness) but the slide contained the explosion just as it should, and there were no injuries. I asked him if it was one of the handloads that did the deed, at which point he held up the offending piece of brass and stated "Nope, factory Winchester." I then examined the pieces of the 52 and noted that the roller from the cracked side of the barrel was out of round and told him that was probably the real offender. A new barrel assembly, and he was right back out on the range and ticking along like clockwork, but with a new-found respect for firearm maintenance.
This whole thing goes right along with the "super-explosive-ultra-hot-Czech-subgun-ammo" myth out there, (I have established to MY satisfaction that there is no such thing...) take it with a grain of salt, and decide for yourself. ANY ammunition at ANY time has the potential to "spontaneously disassemble" ANY firearm, just lookup "Glock Kaboom" in a search engine and you will see many results. But that sure doesn't keep folks from buying and shooting Glocks and claiming that they are the greatest firearm in the whole history of the world. Is it the firearm or the ammunition? The firearm manufacturer says it is the ammo, the ammo manufacturer says it is the firearm, and around and around we go!
What it all boils down to is that it is a personal decision, there are no hard and fast rules when it comes to speculation and personal preference, and the only right answer is the one you decide is right for you.
Thank you very much!
