October 6, 2022 Loading Accurate Pistol Ammo — Smart Tip from the USAMU
Photo courtesy UltimateReloader.com.The U.S. Army Marksmanship Unit (USAMU) has published a series of reloading articles on its Facebook Page. The USAMU’s second article in a 3-part series focuses on loading competition pistol ammunition. The taper crimp is a key element. The quality/uniformity and consistency of the original brass are also important. This article is for you if you shoot pistol competitively or simply want to improve the accuracy of your handguns. Taper crimp tips are extremely important.
Loading Accurate Competition Ammunition — Part 2 Of 3Today we continue our series on factors that affect accuracy in pistol handloads. Part One is available on our USAMU Facebook Page. Scroll down to Part 1 on March 28, 2018, to see the first installment. This article is about semi-auto loading. Revolver crimp techniques can present some very different challenges. To put it simply, different amounts are used with different handloads to achieve the best accuracy. The amount is determined by bullet weight, powder burn rate, and charge. Other factors include case neck tension. Many variables are checked during machine-rest testing of experimental Service Pistol ammo. Our Shop will often vary a load’s crimp by 0.001 degrees. When re-testing for the best accuracy.
A common question is “How do you measure the taper crimp that I’m using on my cartridges?” Measure the case diameter at each edge of the cartridge’s mouth using the narrow end of a dial caliper jaws. To ensure consistency, it is important to take multiple measurements. You should also measure around the case mouth to ensure consistency, as case wall thicknesses can vary. You can measure 2-3 cartridges with the same crimp setting to be certain of the true dimension. However, it is possible to repeat this step later if necessary. For example, a crimp setting of 0.471 may give a measurement of 0.469? Brand X brass might result in 0.469? With Brand Y. For 50-yard Slow Fire, it is important to use brass from the same manufacturer. If brass is available in one lot number, it would be ideal. Because progressive presses use interchangeable tool heads, it is easier to keep separate tool heads for each load. This maximizes uniformity and accuracy.
For pistol accuracy, brass is essential. Although brass can be loaded with ammunition of mixed parentage, it is not the best for accuracy, especially at 50 yards. The serious competitor must pay attention to his brass, even if it is only for the 50-yard “Slow Fire”, portions of “Bullseye”, matches and practice. It is possible to ensure that brass is separated as described above and keep track of how many times a particular batch of cases have been fired. This will help ensure that case neck tension and case length are uniform, especially at 25 yards. The 10-ring in NRA Outdoor Pistol (“Bullseye”) is quite generous, especially for a well-trained shooter with a reliable pistol and load. For the 50-yard “long line”, purchasing and segregating high-quality brass for slow-fire purposes is a smart idea. Use a unique headstamp marking using 1 or 2 colors marking pen ink to keep track of the brass on the line.
To achieve the highest accuracy, cartridge case overall length (OAL), uniformity is crucial. A uniform length case (best measured after sizing), will result in greater consistency in crimp, neck tension and ignition/burn powder charge. The consistency of cartridge case lengths varies from maker to maker. With smaller manufacturers, it can vary from lot to lot. Some manufacturers are more consistent with their dimensions than others. They also have a greater consistency in the hardness/ductility and hardness of their brass. Consider using a Lock-Out die with progressive presses.
We recommend that you use a lock-out device or any other system that can detect double or low charges when reloading pistol ammunition with a Progressive press. Double charges can occur if your progressive is manually advanced. This can have devastating consequences. UltimateReloader.com has a two-part series that explains the operation and setup of the RCBS Lock-Out Die. If a high or low powder charges are detected, this die will not allow loading. The video below shows the setup of the RCBS Lockout Die on the Dillon XL650 progressive press.
