Two-year-old thread, back to life...
One of the beauties of handloading is that it affords us so much flexibility in the loads that we make. But sometimes a square peg insists on remaining... square. That round hole you're eying is not your friend.
Lest anyone get hurt, contemplating the use of reduced loads using slow powders like IMR-4350, I would commend the story "A Case of Abnormal Pressure - and a Search for the Cause," by Roy Smith in the March/April 1971 issue of Handloader Magazine (#30).
For those who might not have that old magazine at hand, the long and the short was that Mr. Smith blew up his .243 Winchester Model 88 shooting reduced loads of IMR-4350. This despite the capable assistance of RCBS and Nosler (who, among other things, made a Cerro-Safe cast of his chamber). Mr. Smith did not ignore the clear and persistent pressure signs he was periodically experiencing with his "light" handloads. But he did rationalize away much what he was seeing.
Part of editor Neal Knox's rather lengthy comment at the end of the article:
"Editor’s Note - No one knows the cause of the reduced load phenomenon, but it is not a figment of some careless handloader’s imagination, as some contend. In private, off-the-record conversations, employees of propellant companies have admitted to me that they have experienced it in laboratory tests, even in pressure guns, but they cannot study it, for they cannot reproduce it at will. The knowledge that the phenomenon does exist, and that although rare it could hurt someone, is the reason why some of the ultra-slow non-canister powders used in some magnum factory loads is not made available to handloaders.
Whatever the cause of the phenomenon, “‘S.E.E.” is not anything to worry about so long as you follow the rule of not reducing slow-burning powder charges more than 10 percent below maximum. Although it’s a rule that can be broken 99 percent of the time, once in a while, under a special set of circumstances, something triggers the phenomenon - we know not what. - N.K."
