LiveLife
Member
I have been pondering about 1KPerDay's situation of inconsistent accuracy with Berry's 40S&W 180 gr plated bullets and came up with a theory to test.
For 40S&W, 180 gr bullet has produced consistently accurate loads for me, even with plated and lead bullets. Although I favored 165 gr FMJ/JHP Montana Gold bullets over 180 gr FMJ/CMJ for match shooting, when it comes to plated bullets for 40S&W, I always recommended 180 gr over 165/155 gr bullet as plated bullets never produced accuracy as good as jacketed bullets. My experience has been similar for Berry's/HSM/PowerBond/Rainier/Speer/X-Treme plated bullets compared to Montana Gold jacketed bullets.
So when 1KPerDay posted inconsistent accuracy with Berry's 180 gr plated bullets, I sent some 165 gr Montana Gold jacketed bullets so a comparison could be made. I figured if the inconsistent accuracy was due to plated bullets, jacketed bullets would produce greater accuracy. Well, the MG jacketed bullet loads did produce better shot groups but for me, range test results made me ponder some more - http://www.thehighroad.org/showthread.php?p=9235005#post9235005
In theory (without factoring mechanical inconsistencies from pistol parts), accuracy and smaller shot groups result from more consistent chamber pressures which produces more consistent muzzle velocities.
So while replying to another thread about inconsistency of published load data, I wondered whether using mixed range brass with different case wall thickness and different degrees of work hardening with varying amounts of case wall spring back would produce different amounts of neck tension? Different amounts of neck tension would result in different amounts of bullet setback when the bullet bumps the feed ramp. Different amounts of bullet setback would produce varying bullet seat depths that may result in different chamber pressures which will produce different muzzle velocities that will translate to more inconsistent shot groups and decrease in accuracy. So I offered to send verified once-fired brass with same headstamp so accuracy/consistency could be better tested using cases with similar neck tension/bullet setback - http://www.thehighroad.org/showthread.php?p=9238776#post9238776
What are your thoughts on this?
Could different amounts of neck tension/bullet setback produce enough variations in chamber pressures to affect accuracy that are measurable?
I am thinking about testing this theory by range testing mixed cases with different post-sized ID at case mouth and verified once-fired same headstamp cases with same post-sized ID at the case mouth.
For 40S&W, 180 gr bullet has produced consistently accurate loads for me, even with plated and lead bullets. Although I favored 165 gr FMJ/JHP Montana Gold bullets over 180 gr FMJ/CMJ for match shooting, when it comes to plated bullets for 40S&W, I always recommended 180 gr over 165/155 gr bullet as plated bullets never produced accuracy as good as jacketed bullets. My experience has been similar for Berry's/HSM/PowerBond/Rainier/Speer/X-Treme plated bullets compared to Montana Gold jacketed bullets.
So when 1KPerDay posted inconsistent accuracy with Berry's 180 gr plated bullets, I sent some 165 gr Montana Gold jacketed bullets so a comparison could be made. I figured if the inconsistent accuracy was due to plated bullets, jacketed bullets would produce greater accuracy. Well, the MG jacketed bullet loads did produce better shot groups but for me, range test results made me ponder some more - http://www.thehighroad.org/showthread.php?p=9235005#post9235005
In theory (without factoring mechanical inconsistencies from pistol parts), accuracy and smaller shot groups result from more consistent chamber pressures which produces more consistent muzzle velocities.
So while replying to another thread about inconsistency of published load data, I wondered whether using mixed range brass with different case wall thickness and different degrees of work hardening with varying amounts of case wall spring back would produce different amounts of neck tension? Different amounts of neck tension would result in different amounts of bullet setback when the bullet bumps the feed ramp. Different amounts of bullet setback would produce varying bullet seat depths that may result in different chamber pressures which will produce different muzzle velocities that will translate to more inconsistent shot groups and decrease in accuracy. So I offered to send verified once-fired brass with same headstamp so accuracy/consistency could be better tested using cases with similar neck tension/bullet setback - http://www.thehighroad.org/showthread.php?p=9238776#post9238776
What are your thoughts on this?
Could different amounts of neck tension/bullet setback produce enough variations in chamber pressures to affect accuracy that are measurable?
I am thinking about testing this theory by range testing mixed cases with different post-sized ID at case mouth and verified once-fired same headstamp cases with same post-sized ID at the case mouth.