Re: Lee Collet neck sizing vs Redding neck bushing die
Of all the .223 dies I tested for run out using a factory chamber, the Redding FL "S" die is the worst, and the Lee Collet neck die is the best.
I handload 50 cartridges, 30 for rifles.
When I get a new cartridge, I buy 1) the reamer, 2) the Lee Collet neck die, 3) the Forster seater die, and 4) the Forster FL die with the neck honed out at the factory.
Sometimes I get custom reamers for tight neck no turn. Sometimes I buy off the shelf SAAMI reamers, but I am not buying any more Redding S dies.
The factory chamber makes the case neck much bigger. The floating bushing in an "S" die bends the neck toward the side of the neck with thicker walls. The bent neck introduces the bullet to the bore with the center of gravity not in the center of the bore. The rifling spins the bullet and upon escapement, the bullet is flung off center of the bore, thus increasing group size.
From the NRA and the US Army after 1950 on bullet tilt:
<span style="font-style: italic">MATHEMATICAL SOLUTION
A laterally displaced center of
gravity moves through the rifle bore
in a helical (screw) path. The pitch
of this helix is the pitch of rifling,
and its radius is the lateral displace-
ment of the center of gravity. On
leaving the muzzle, the center of
gravity continues in the direction it
had at that point. For example, if it
leaves at top of the bore and rifling
is to the right, the departure will be
to the right. The bullet travels ap-
proximately 2l.5" in a 24" barrel,
making 2.15 turns in the 10" twist
of rifling. The number of turns
shows the orientation on emergence
compared with that in the chamber
before firing. The angle of emer-
gence is that angle whose tangent is
2 pi times the lateral displacement
divided by the rifling pitch. For
.004" point displacement and I0"
rifling pitch, the tangent is 1/8(2·pi)
(.004)/l0 and the corresponding
angle is 1.1 minutes.
The displacement on target from
this cause is proportional to the
range and can be obtained without
noting the angle. For example, ,004"
point displacement gives in l0"
rifling pitch, so far as this mecha-
nism goes, a target displacement at
100 yds. (3600") indicated by the
proportion .00l· pi /10=X/3600, from
which x =1.1".</span>