If one shot is 100+ fps off, first suspect inconsistent powder charge or a bad primer/case (weigh a sample of charges, inspect primers, sort brass), but also rule out shooter flinch, barrel temp/fouling, or a bad scale — a chronograph reading that large usually means a real load/ignition...
A bit of extra smoke can be normal—slower powders like IMR4350 often produce more muzzle flash/smoke than factory ammo; just confirm you used published charges/OAL and safe pressures, compare velocities, and if still concerned try a milder powder (or slightly reduced charge) and repeat.
Don’t fire if the overall length exceeds the limit — adjust bullet seating depth with the die, trim or turn the case neck if needed, or use a shorter bullet. If it’s still too long, check chamber headspace or have a gunsmith measure it before continuing.