Bula:
Stand 5 different 230 gr bullets from, lee, rcbs, lyman, H&G and Saeco next to one another--they vary in overall height, maybe not so much in weight.
OCD1:
I found it interesting and confusing at the same time all the different OAL for a common 230 gr LRN in a 45 ACP.
Yes, there are different test parameters and slight differences in the bullets but really, how much difference is there in brands of 230 gr RN?
Yes, I know about dropping the bullet in the barrels for determining best fit, but for such a common bullet shouldn't there be more consistency?
OCD1, when powder manufacturers test their powders using different types and make of bullets, they don't even use pistols - they use different length barrel "fixtures" that were designed to measure chamber pressure.
As Bula posted, different bullet types have varying lengths and differ as to how much of the base will be seated inside the case. How deep the base of the bullet is seated directly affects chamber pressure and burn characteristics of powder.
I bet you the powder manufacturers identify the starting load and OAL of the particular bullet tested based on the minimum chamber pressure that produced reliable powder burn and consistent shot groups. Of course, they would identify the max load and OAL that did not exceed the SAAMI limits for that particular caliber case design.
They may do some testing in some pistols to determine reliable slide cycling and case ejection but not how well the loaded rounds will feed/chamber from the magazine for all pistol/barrel combinations. Their job is to provide safe chamber pressure data without exceeding the SAAMI limits. For OAL determination that feed/chamber well in our pistols/barrels, THAT's the reloader's job.
Max load definition from
SAAMI glossary page:
CHARGE, MAXIMUM
The greatest charge weight, in grains, of a particular propellant that may be used with other specified ammunition components without exceeding the safe, maximum, allowable pressure limit for the specific cartridge or shell being loaded.
For me, I first determine the OAL that feeds/chambers well from the magazine for a particular pistol/barrel combination then work up the powder charge from the starting load that produce the most accurate shot groups without exceeding the max load.
You are always going to have an OAL range that will feed/chamber reliably for a particular caliber of bullet and pistol/barrel combination. For 230 gr RN 45ACP, I have loaded them from 1.245" to 1.27" OAL in various pistols/barrels reliably.
So, if you are reloading your own rounds, what determines the final/optimal OAL that you end up using? Well, since I use Pro Auto Disk with pre-set powder charge drops, I may adjust the OAL to "fine tune" my chamber pressure - accuracy of shot groups.
Example:
If a particular load I want for a specified bullet calls for 5.0 gr at 1.26" OAL but Pro Auto Disk will drop 4.9 gr, I may decrease the OAL just a bit (say 1.25" vs 1.26"). If the next Auto Disk hole drops 5.1 gr, I may increase the OAL to 1.27" vs 1.26".
In general, longer the OAL, the more accurate the load will be since the bullet's bearing surface will engage the rifling sooner without having to "hop" into the rifling.
BEARING SURFACE
That portion of a bullet’s outer surface that comes into direct contact with the interior surface of the barrel bore when moving through the barrel.
But this is not often the case. When I first ordered my test 45ACP lead bullets from Missouri Bullets last year to try them out, I ordered 18 BHN 200 gr SWC and 200 gr RN (I had plenty of 230 gr RN from my retired lead bullet caster at that time so I didn't order any). I knew that 200 gr SWC has been a known accurate bullet design, but wanted to try the 200 gr RN for other shooters who shot XD pistols. Well, I tried different OALs from 1.190" to 1.25" using 4.9 gr W231/HP38 and found the shorter 1.190"-1.195" still fed/chambered well in my pistols (especially in XDs) and produced the most accurate shot groups from test loads that rivaled SWC shot groups. This maybe due to increased chamber pressure from bullet seated deeper into the case and resulting in more accurate shot groups. So, as long as the OALs feed/chamber well in your pistol/barrel combination, determine the final OAL that produce the most accurate shot groups. I use the longest OAL that will feed/chamber well for specific purpose pistol/barrel combo - like match shooting/match practice ammo.
But for "general purpose range/plinking loads" to shoot in multiple pistol make/models, I use the following to ensure they'll feed/chamber well.
9mm RN - 1.125" OAL
40S&W TCFP - 1.125" OAL
45ACP RN - 1.25" OAL
