Forster Neck Bushing 0.338" (BUSH-338)

Description

From Forster
Forster Our Bushings for the Bushing Bump Neck Sizing Dies are Smooth as Silk and Cryogenically Treated. An ultra-smooth bushing produces better loaded rounds. We use a super cooling Cryogenic treatment to finish our bushings, which are comparable to or even superior in, smoothness to coated bushings. Cryogenic treating produces filler particles that refine and close the grain structure of the steel. This denser metal structure creates a greater surface area, thus reducing both friction and wear. After the bushings are heat-treated, they are cryogenically treated in an aircraft-quality lab. The steel is subjected to a precisely controlled slow cooling process which eventually reaches an extremely cold threshold. The bushings are then slowly warmed to room temperature and cycled through a controlled heating process. The result is increased wear resistance, improved dimensional stability and prolonged life.
Rule of thumb for choosing bushing sizes
If you are single loading into a bolt gun you want 0.001” spring back.
If you are loading a bolt gun from the magazine you want 0.002” spring back.
If you are shooting in an autoloading rife you want 0.003” spring back.
How do you measure?
Well, you can take the caliper and measure a loaded round at the case neck on three different round.
Then average that number.
Then subtract the amount of spring you want.
Example
Case neck of loaded round measures:
.3378
.3380
.3379
Sum of 1.011”
Divided by 3 =.338”
Less 0.002 for loading out of magazine in a bolt gun = 0.336 bushing
Or
You can take a ball micrometer and measure a handful of empty cases
And come up with an average of the neck wall thickness.
With this average… say 0.015” multiply by 2 = 0.030”
To this you add the bullet diameter of .308
And, you have .338”
Less 0.001 for single loading in a bolt gun = 0.337” bushing