Knowledgebase
Bulged Pistol Cases near the base
Posted by on 13 August 2015 03:20 PM

Bulged cases are usually caused by the sizing die squeezing the case down too far in diameter for the bullet used. Measure the case mouth inner diameter after the case has been sized, and after the case mouth has been flared. It only needs to be .001 to .002 under bullet diameter for a tight bullet fit. 

If the case mouth inner diameter is less than .001 -.002 inch under bullet diameter, the bullet will push out more on the weakest side of the case as it is seated. This is because cases are rarely the same thickness and/or hardness all the way around the circumference of the case mouth. The fix is an oversized sizing die, or smaller bullet diameter.

Bulged cases are cosmetic only and pose no danger in shooting.

There are a couple of reasons that most resized cases will have a slight bulge just above the rim. When using conventional resizing dies the case will have to be pulled back out of the die, thus a shell holder. The shell holder stops the resizing die 1/8" above the rim. There is also a radius at the base of the resizing die. This is there to lead the case into the die. This radius accounts for approximately one-eighth inch also. This results in the bottom quarter-inch of a case not being resized with a conventional die.

We have a product available to fix this issue for the following cartridges: .380 ACP, .40 S&W, 10mm, .41 AE, .45 ACP. .45 Win Mag, and .45 GAP Calibers. it is a push through die, so it will reduce a case diameter back to specification for the entire case length, where most other dies that use a shell holder can not. You can reduce the effort required to push the case through the die by raising, or backing out the die. You want to just push the rim through the die at the very top of the stroke. This is where you have the most mechanical advantage. You will also require a Factory Crimp die in the caliber you are removing the bulge from. Bulge Buster P/N 90487