mggunner34 wrote:yes yes I know the whole cheap ammo speech but lets get off that for a moment here, its POPPING out the primers on both yugo and Romanian, how could using more expensive ammo change that?
You're considering the wrong failure mode, IMHO. For starters, for the primers to "literally pop out" as you say, they have to physically have ROOM to do so. In a normally functioning MG34 bolt + cartridge face relationship, the external primer annulus is fully supported under the entire high-pressure event cycle, i.e., there is a full circumference physical bolt face contact on the exposed primer annulus, which is maintained well after the high pressures have subsided. This full support is achieved by tight contact between the cartridge rear area, and the bolt face itself, broken only by the area opened up where the FP protrudes through, IOW's under normal circumstances of operation there is simply no possible room for the primer to be PUSHED rearward out if its pocket under HIGH PRESSURE, the only thing which will do that.
While certainly some suspect ammunitions may exhibit loosened primer retentions, the fact that BOTH diverse types of ammunition here are exhibiting the same failure mode speaks volumes- you have a serious pressure-related event occurring where the required lock-up between the bolt-face and cartridge face is not being sustained well into the extraction phase. The bolt is partially opening under high-pressures, allowing the primers to de-seat and be PUSHED OUT of their pockets, crimped or not.
Okay, so what causes this? Fortunately, it is a rather easy situation to analyze and fix. You'll recall that the design of the "Solothurn lock (Stange lock)" employed in the gun utilizes NON-POSITIVE threads, i.e, they tend to NOT stay locked tight because the mathematical pitch of the threads leads to induced pressures causing the threads to begin anti-rotational unlocking.....stated simply, under high pressures they tend to open up against the inclined plane of locking rotation. This allows the bolt(and bolt face) to begin rotational unlocking before residual chamber pressures have dropped correctly(safely) and as the bolt increases its space rearward relative to the cartridge face (now no longer fully supported), the high residual pressures press directly against the primer annulus forcing it out of the primer pocket. That is why you are seeing the same symptoms across the differing ammunitions.
This was a known issue when the gun was designed and they designed in a very simplistic and very effective cure to combat the premature unlocking tendency in the form of a "bolt lock latch" which is/was merely a heavily spring biased arm that presses against the right bolt lug, effectively positively preventing undesired rotation until it is moved out of engagement by a cam in the recoil phase, by clearing a lug on the barrel jacket interior as the barrel extension + bolt move rearward in the initial recoil phase. These springs DO wear and lose their original rated biasing force, so replacement of the spring is called for here. If not the spring being at fault, even simpler is that the actual locking latch ARM itself may have broken, be damaged, or even missing.
These are all very simple things to either repair or replace, and having access to one of John Baum's excellent manual translations will easily allow you to do the work quickly. Spare parts here are easy to find.
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