Hello,
The HV (No-Jam) magazine was developed for the M27-30. It was marked HV.
They then became standard on the M39 and the "HV" marking was done away with. I don't know why this was so, but I
assume because the standard magazines were take out of service. I don't know this for a fact.
A standard mag looks like this:
Courtesy 7.62x54r.net
And an HV mag looks like this:
Courtesy 7.62x54r.net
The interrupter should prevent rimlock. However, it sometimes does not due to a variety of reasons. For example, I have found that the one piece interrupters tend to be slightly shorter. Replacing my two-piece with a one-piece led to occasional rimlock.
The solution, in my opinion, is ingenious in its simplicity: The dimples in the magazine force the round directly below the interrupter backwards so that its rim is contacting, or almost contacting, the rear of the magazine. The top round, the one on top of the interrupter, cannot therefore get its rim locked behind the one below.
It serves mainly as a failsafe backup to and works with the interrupter. However, it works. I've
tried to induce rimlock since installing one in my 91/30 a couple years back and I simply cannot.
The HV mag is the only one that is correct on the Finnish M39. The M27-30 usually has the earlier version that's actually marked with "HV".
I'm a huge fan of the Finns and their methods. With shimming, triggers, etc; they've made the Mosin into what it should be. Even their M39 stocks are much more ergonomic, what with the pistol grip and all. (Earlier M39 stocks do have the straight wrists, but the majority have the pistol grips.)
Where the Russians viewed the rifle as a vehicle for the bayonet, the Finns were and are riflemen like us in North America and their rifles and methods reflect this.
Regards,
Josh
