Bumping Bullets

[LuvSkye]

I have heard this before but don't know exactly what how and why?
Can anyone explain?

Thanks
LuvSkye

[Castaway]

The term can mean two different things, but both end up increasing the diameter of the bullet in question.  Dies can be made whereby you place a cast bullet in and tap it with a hammer or press, swaging the bullet to fit, either increasing the diameter or even the nose shape.  Not too common though.  It is also called "bumping" when you fire a bullet and the pressure causes the base to obturate, thus filling the barrel better.  This is a common cause of leading with cast bullets.  Shooters buy into the HARD bullet propaganda and shoot bullets too hard for the pressure of a load.  If the bullet doesn't obturate, gasses blow by, the bullet doesn't engage the rifling and lead is deposited, givein cast bullets a bad name.

[haroldclark]

Bumping Cast Bullets      02/25/04

About 15 years ago, I bought a Hanned Company (different name then) 308 bumping die and I still have it.

The nose section of the bullet is bumped to a particular shape so as to become a bore riding type.  You put a bullet in the die and with a nose punch and you tap it with a mallet.  This process seemed to me to be a Mickey Mouse way of doing it.  If the die would fit in a press, you could set the amount of pressure with the throw of the handle.  With a hammer, it is guess and guess again if it is equal to the last shot.

I wanted the bullet to have more bearing surface.  The bullet I used was from an RCBS 150-grain gas checked cast bullet.  I tired it with different percentages of wheel weights, tin and linotype to find a proper medium.

After all was done, the bumped bullet did not group as well as the un-bumped ones.  The mold cast a bullet that was just at 308 caliber and it did not shoot as well either way as the Saeco #316 150-grain cast bullet.

The results did not justify the effort and time consuming process.

If you want a great cast bullet for 30-30: Saeco #316 150 grain 308.

For other 308 uses, the #316 Saeco 173 grainer will shoot under an inch in most any 30-caliber gun.  I use it in a Remington Semi-Auto model 742 in 30-06 and it shoots under an inch.  I cast the bullets with wheel weights and 2% tin, or 3 pounds of ww + 1 pound of linotype.  The gun doesn't care.  With the #315 Saeco Bullet, it chronographs at 1811 fps.  No leading and I cleaned it for the first time after 1400 plus rounds of cast bullets.

I used to use a Saeco #310 (210 grains)  bore riding bullet (dog dick) in the 30-06 and it chronographed at 2012 fps and 2179 fps with different loads.  I settled on the 2012 fps load with 25 grains Reloader 7 with that bullet and then I went to the #316 'cause I have a 4 cavity mould for it.  I shoot this load out to 547 yards with great accuracy.

I used the 316 bullet in the 30-30 Marlin micro grooved.  Shoots like a champ with 1.5" groups at 100 yards.  I also, use that bullet in my 10" Thompson Center Contender and it will shoot under an inch.

Well, I got off the subject there.  Since I used the bumping die in 308, I went there. I'm sure it won't hurt.

Harold Clark