I've been shooting Mosins now for a year or so, and though I am an ardent handloader and have been for 30 or so years, I buy alot of Milsurp ammo because it can be quite cheap. Thusfar, for my Mosins, I've purchased Czech Light Ball, Hungarian Light Ball, Bulgarian Light Ball, Bulgarian Heavy Ball and a case of the U.S. Gov't contract stuff from CDNN (JMS). Though I've owned several Mosins, I have owned a '39 Tula for quite a while now and have fired all types of ammo through it including handloads. It is a very accurate rifle especially with handloads.
I buy the surplus ammo because it's cheap shooting, but honestly, I bought most of this stuff for components, and since I have a range at my house and love testing ammunition for its accuracy ability, I shoot alot. The Czech stuff really didn't shoot too well, nor did the Hungarian. The Bulgarian Light was odd; of 10 shots, it'd group may 6 or so nicely and sling 4 out of the group. I disassembled the ammo and found quite a bit of variation in bullet weight and diameter. This probably explains the flyers. Handloads with the pulled and weight sorted light Bulgy bullets shot well. Had pretty much the same experience with the Bulgarian HB, but the bullets seemed to be held to closer tolerances. The (JMS) was quite accurate, but even more so if I broke the ammunition down and carefully reassembled the components.
I tried handloading pulled steel core bullets, but accuracy was lacking.
Given this, I've noticed that the lead core ammunition (Bulgarian LB & HB and JMS) was more accurate than the steel core (Czech and Hungarian LB). I then remembered reading something in one of my Handloader magazines. It was regarding lead core bullets vs. the Barnes X which is solid copper. The author made the point that very often the solid copper bullets do not begin to shoot accurately until pressures approached maximum. This is due the fact that bullets, when kicked in the butt with tens of thousands of pounds of pressure combined with overcoming the atmospheric pressure present in the barrel, tend to become "squashed", for lack of a better term, and take the shape of the inside of the barrel. This phenomenon is illustrated in, I believe, the Lyman #46 Reloading handbook.
Obviously, a bullet made of solid, albeit soft, copper would require much more pressure to obturate or form to the bore than would a lead core bullet with a thin soft copper jacket. So it would seem that a steel core bullet would retain its shape (not obturate)when fired due to the hardness of the steel core. So, unless you had a steel core bullet that closely fit the barrel, it seems to me that there would be a potential for poor accuracy.
In my mind, this would explain why lead core bullets, at least for me, tend to shoot better than steel core bullets. Maybe at this point I should elaborate on my criteria for accuracy.
I do all of my shooting at 100 yds. as I don't have a 50 yd range (yet). When I begin to seriously check a rifles accuracy potential, I'll normally use my own cast bullets because they can be sized to a rifles barrel (groove diameter)which removes one of the elements of poor accuracy; undersized bullets. If the rifle shoots well with cast bullets, then I'll try surplus ammo. At 100 yds. I deem anything over about 3 1/2" as unacceptable. That may sound stringent, but I want to hit where I aim.
So my question is: Has anyone else noticed the tendency of lead core ammunition being more accurate than steel core? I understand that good steel core ammo will be more accurate than poor lead core, but generally speaking, anyone seen any tendencies? What I'm looking for here is people who've fired different kinds of MilSurp 7.62x54r in the same rifles. NOT "Well, my Mosin loves AlBulHungian Medium Ball steel core, but I haven't tried anything else...."
Looking forward to input!