Current Limitations
Currently, the 5mm bore suffers from
inadequate development. For example, most of the bullets available
are marginal or sub-marginal for use with full-power 5/35 loads in
a 1/12 twist barrel (default standard for 5mm), which is necessary
to stabilize 40-grain bullets. Heavier bullet jackets are needed.
In my humble opinion, the real issue is perception. The 5mm should
not be considered a "long-range" varminting option. For this reason,
the 40-grain bullet is unnecessary.
Had Hornady standardized a 35-grain bullet as the "heavy" option for the 5mm bore, they could have chosen a 1/14 twist and we would then find that all 30, 32, and 35 grain bullets now offered would work fine, even with the hottest loads in the 5/35. Bullet makers will get this sorted out. When Nosler offers a BT at 30-grains (or less!) we will have a bullet that will really bring the 5mm to the forefront, I am sure. Meanwhile, I am using a 1/16 twist Pac-Nor barrel on my Savage Custom Shop 5/35. Ballistics and accuracy with the 32-grain Sierra BK are impressive, to say the least. See associated ballistics graphs. I can suggest that anyone planning a custom 5mm might want to consider a 1/14 twist for use with light bullets.
Recoil is so modest that I can literally see the paper slap when the bullet hits it at 100 yards! I have modified the stock on this gun to reduce muzzle climb (I changed the taper angle on the foreend and the buttstock), which helped in this regard – the gun hardly moves anyway. This is my new varminting combination. When one considers the ballistics, it is hard to see what could be better: BC = 0.22; velocity = 4650 fps.