Hangun Corner: Wnat’s the best crimp?



Originally Published in the Oct, 2014 Newsletter

QUESTION: What’s the best crimp for a handgun cartridge? Roll crimp or taper crimp? No crimp?

ANSWER: First of all, a roll crimp is where the edge of the case is rolled over onto the bullet. A taper crimp squeezes on the bullets. Secondly, a crimp is essential to keep bullets from moving forward out of the cases when one round is fired from a revolver. In a semi-auto, a crimp is important to keep the bullets from moving back into the case as the handgun is fired and the slide moves back and forth. Essentially, crimp addresses reliability of ammunition. Not crimping is not recommended.

Crimps are also important to insure proper ignition of the powder charge. Additionally, in semi-autos head space is controlled by the cartridge case length so the crimp will have an effect. In revolvers, most cartridges have rims so head space with a crimp isn’t critical

The type of crimp, roll or taper, does not affect accuracy; e.g., the .38 caliber wadcutter factory ammo is beautifully roll crimped, and it is accurate out of both revolver and semi-auto.

For lead bullets, use a light crimp. Just enough so you can’t push the bullets into the case with your finger. Too heavy of a crimp will change the diameter of the bullet and even damage the driving bands of the bullet. Accuracy will suffer. Remember, there are soft swage commercial lead bullets and hard cast lead bullets. The hard cast bullets are normally .357 semi-wad cutter (SWC) bullets. The .38 Special bullets are normally swaged soft lead. Many of these are generally full wad cutters (WC). They should have a very light crimp. For jacketed bullets, you can use a heavy crimp on the cannelure. You wouldn’t damage the much harder jacketed bullet. Again, if you can push the bullets into the case with your finger, then the crimp is too light.

Many semi-auto shooters will still have feeding problems with either roll or taper crimped ammunition. In most cases, it isn’t the crimp but likely feeding ramp problems.

While neither roll nor taper crimp can claim to be more accurate, many believe taper crimp has an edge on reliability. Buying dies and have a choice? Get a taper crimp. Already got dies with a roll crimp? Don’t worry. Work on the shooting skill instead.

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