Thread: How fast/effective?

Originally Posted by shooternz

Use some of those 170 grain cast bullets start at 27 grains 2206H and work up to about 35 grains or 1800-1900 fps they expand at 1500fps the recoil is light
at that velocity, The 151HP are dynamite at that velocity

Worth stressing that a 170 grains heavier boolit does not necessarily equate to bigger recoil. Cast non-jacketed bullets require a third less powder charge for same velocity, and the velocity run at is lower in any case (because of limitations of the strength of lead vs rifling grooves). As shooternz points out, cast HP boolits are good (better) at expanding, even at quite slowish velocities.

As an aside (I initially misread the post, thinking someone was considering heavy boolits in an 7.62 Soviet rifle). Heavy boolits in a 7.62x39 rifle. When the 7.62x39 round was adopted by the Soviets in the 1940s, they went for a 1:9.45" twist which was copied straight from the 7.62x54R Mosin rifle. Same rifling machines making different / same-same barrels. This fast twist was originally adopted to stabilise heavy 210 grain round nosed projectiles, but reincarnated in the x39s spinning 126 grain bullets it is just too fast - actually deleterious to accuracy, so some modern manufacturers offer 7.62x39's with slower twist rifling for that reason.
The traditional 7.62x39 barrel has an inherited/throwback ability to stabilise heavy, long slugs with a fast twist it has no need for with standard milspec ammo (except perhaps for longer tracer bullets). A heavier bullet will do just fine in the standard 7.62x39 fast twist barrel, in fact it will feel strangely and unexpectely at home with a just fine twist rate.