By Steven Hurst, exert from Fouling Shot 143-20. Jan-Feb 2000.
When I started loading match cast bullet ammunition for the .45 ACP, I naturally sought out the advice of the top shooters that were rolling their own with home cast slugs. The odds-on favorite bullet was the Hensley and Gibbs #68. The plain base/bevel base users ran about 50/50, I chose the plain base version and ordered a 4cavity mold. When it came to loading those big, beautiful 200 grain semi-wadcutters, there was no argument, all the participants agreed that best accuracy was to be had when the bullet was seated to contact the leade.
However, what caused the accuracy improvement divided the shooters into two camps, and the arguments were hotter than the ones I started with the plain base/bevel base question. Both camps had plenty of argument ammunition and a shortage of facts, which always makes for a hot time in the clubhouse. One group proclaimed it was the reduction of headspace that made the groups smaller, the other fervently held that the elimination of bullet jump to the rifling was the ticket. The headspace group pointed out that .45 ACP cases were always way under maximum length. They had the support of the revolver shooters who could show poor accuracy any time by shooting their S&W 45 ACP revolvers without moon clips, which increased headspace and swelled groups. The bullet jump believers pointed out the apparent lack of any headspace effect with jacketed bullets.
The point was moot as far as I was concerned, what I wanted was the results. However the idea kept churning in my head, and I measured hundreds of .45 ACP cases hunting for a few maximum length cases that could have settled the argument. I can only conclude that the factories make them short on purpose as none approach the maximum length and many are even shorter than the trim-to length. Lacking long cases, the idea languished for years.
After the 9X19 Luger was banned as an IPC major power load, the 9X21 cartridge became available and provided an opportunity to find the answer. Using the slightly longer 9x21 cases, I trimmed one batch to 0.760”, giving zero headspace in my SIG 225. A second lot of cases were trimmed to 0.748”, equal to the average of commercial cases, giving 0.012” headspace. Each lot of cases were loaded with the same cast bullet load, one half with the bullet seated to rifling contact and the other 0.070” deeper.
When I started loading match cast bullet ammunition for the .45 ACP, I naturally sought out the advice of the top shooters that were rolling their own with home cast slugs. The odds-on favorite bullet was the Hensley and Gibbs #68. The plain base/bevel base users ran about 50/50, I chose the plain base version and ordered a 4cavity mold. When it came to loading those big, beautiful 200 grain semi-wadcutters, there was no argument, all the participants agreed that best accuracy was to be had when the bullet was seated to contact the leade.
However, what caused the accuracy improvement divided the shooters into two camps, and the arguments were hotter than the ones I started with the plain base/bevel base question. Both camps had plenty of argument ammunition and a shortage of facts, which always makes for a hot time in the clubhouse. One group proclaimed it was the reduction of headspace that made the groups smaller, the other fervently held that the elimination of bullet jump to the rifling was the ticket. The headspace group pointed out that .45 ACP cases were always way under maximum length. They had the support of the revolver shooters who could show poor accuracy any time by shooting their S&W 45 ACP revolvers without moon clips, which increased headspace and swelled groups. The bullet jump believers pointed out the apparent lack of any headspace effect with jacketed bullets.
The point was moot as far as I was concerned, what I wanted was the results. However the idea kept churning in my head, and I measured hundreds of .45 ACP cases hunting for a few maximum length cases that could have settled the argument. I can only conclude that the factories make them short on purpose as none approach the maximum length and many are even shorter than the trim-to length. Lacking long cases, the idea languished for years.
After the 9X19 Luger was banned as an IPC major power load, the 9X21 cartridge became available and provided an opportunity to find the answer. Using the slightly longer 9x21 cases, I trimmed one batch to 0.760”, giving zero headspace in my SIG 225. A second lot of cases were trimmed to 0.748”, equal to the average of commercial cases, giving 0.012” headspace. Each lot of cases were loaded with the same cast bullet load, one half with the bullet seated to rifling contact and the other 0.070” deeper.
The loads were fired alternately with barrel cleaning and fouling shots between each ten shot group. Velocity measurement, during the accuracy testing, showed no significant difference. The results, shown in the table, are very decisive. The long, zero headspace cases did not produce significantly better accuracy. It did not matter which cases were used, the seating of the bullets to contact the leade was the factor that was responsible for the smaller group size.