Ruger 15151 is absolutely correct. BTW, if you do consider using someone else's comparator data, you should be sure that their firearms, gear and setup is identical to yours. Otherwise, they won't be comparable! That's because with a comparator, the cartridge base to ogive length (CBTO) is being measured, not the overall length of the cartridge (COAL). Clear as mud, I'm sure.
sparkyv,
You are correct that "That's because with a comparator, the cartridge base to ogive length (CBTO) is being measured, not the overall length of the cartridge (COAL)".
However, I was not suggesting that bantam9 blindly use my comparator data, but to establish for himself that the overall length of the cartridge (COAL) when measured from cartridge base to bullet tip varied by what ever amount (my example was "COL may be +/- 0.004" was only an example) that the comparator would show that the cartridge base to ogive length (CBTO) would be LESS of a difference.
This means that although the overall length of the cartridge (COAL) may be off by (EXAMPLE: +/- 0.004") the cartridge base to ogive length (CBTO) may only be off by (EXAMPLE: +/- 0.002").
If you have correctly followed "finding max coal using your barrel"
https://www.thehighroad.org/index.p...rel-find-a-max-o-a-l-with-your-bullet.506678/
THEN finding your correct WORKING COAL, you will have a safe COAL.
The OGIVE is what binds on the rifling in your barrel when trying to find your CARTRIDGE MAX LENGTH.
You do not need "be sure that their firearms, gear and setup is identical to yours."
When you establish YOUR WORKING COL FOR YOUR GUN, using YOUR firearms, gear and setup, you can then use the comparator to determine YOUR cartridge base to ogive length (CBTO) with YOUR selected COL, using YOUR firearms, gear, setup, brass and bullets.
This gives you a BASE LINE CBTO measurement that you can compare with cartridges that are over/under your YOUR selected COL.
It has been MY experience that the when YOUR DETERMINED overall length of the cartridge (COAL) is off (EXAMPLE: +/- 0.004") that you will find that the cartridge base to ogive length (CBTO) is less than the variance of the COAL.
This difference could be attributed to several factors such as variation of bullet nose length in plated/fmj bullets in the same lot to the coating differences on the nose of a coated lead bullet.
They don't make a comparator for 9mm because it isn't necessary. Maximum / Working OAL will be different in every chamber depending on how short it is "throated" (distance from the end of the chamber where the shell case locates and the barrel riffling. Just use the "Plunk Test" to learn the max OAL for your barrel. Then you need to determine working OAL from there because Maximum OAL doesnt necessarily cycle in every gun.
Here is a helpful link explaining how to determine your max OAL/COL:
https://www.thehighroad.org/index.p...l-with-your-bullet.506678/page-2#post-8864541
You will need to do this with every bullet you use to reload because they all have a different profile. I load at least .010 from the bullet hitting the riffling to allow for variance in shell case lengths. Once you have determined the Maximum/Working OAL, just keep a dummy round so you can set up your dies quickly when you change between bullets weights and profiles. If you have multiple 9mms, most will require a different Maximum / Working AOL. You will have to find the 9mm pistol that requires the shortest and then load that OAL for all the 9mm pistols you have.
Hope that helps! Good luck!
I strongly agree with what Ruger 15151 said in his post!
Anyone care to share what their OAL is with RMR's new 124 gr FMJ?
I run the 124 gr 9mm Match round nose at 1.150 oal, and they shot great, but this new 124gr FMJ has a different profile. Hornady doesn't make a comparator insert for .355 best I can tell.
I would love to compare length at ogive from these 2 projectiles, and use it as starting point for the new RMR 124gr FMJ, unless others would share their OAL's on the new 124FMJ.
The way I read the OP's question is 2 parts:
1)"Anyone care to share what their OAL is with RMR's new 124 gr FMJ?"
ANSWER: IMHO Every gun barrel may need a different OAL so asking for shared COL's may not work in your gun and every bullet will need different OAL to work in your gun barrel.
2)"is there a Hornady comparator insert for .355" (9mm) that I can use to compare "the 124 gr 9msm Match round nose at 1.150 oal, and they shot great, but this new 124gr FMJ has a different profile".
MY ANSWER: IMHO The Hornady comparator insert 30 could do that.
(to quote sparkyv) "Clear as mud, I'm sure".
YOUR MILEAGE MAY VARY
JD