Tom Acheson
posted this
21 February 2023
This is a goofy “forum site”. I typed the following, was almost done, and had to step aside to shovel some snow. I came back and it was gone! Not the first time this happened. Have to get into the habit of developing the text in Word and when finally done, cut and paste it into the reply box.
At one time I “bumped” cast bullets for .30 and 6.5mm caliber. My “coach” (Dick Reese) in 2005 told me to do this: Bump the bullet, the nose along with the ogive, down to the middle of the driving band on the underside of the lube groove. This results in the bullet having a long, very gradual “taper” for much of its length. Then this “taper”, when the round is chambered, enters the mating “taper” in the chamber. Supposedly, a taper in a taper is a good step towards uniform round/bore concentricity.
This was for either an Eagan or an LBT bullet, both with similar profiles, 165-180 grains.
This approach worked very well in my XP-100 chambered in 30 PPC.
Comparing match results, when using my Savage .308 Winchester (Low Profile Varminteer), the groups were always much better with bumped bullets, compared to un-bumped bullets.
My current round in this XP-100 is a .22 BR but so far, no bullet bumping. However, my bump press is currently set-up to size the .22 bullet noses, my first experience @ doing this exercise. Lots of fun down the road!
Tom