I can't find any book data for the RMR hybrids... However XTP data is everywhere. I measured several XTP and they avg about 0.571" and the RMR hybrids measure about 0.545", am I mistaken that if I seated the RMR to 1.060" per my book it wouldn't kill me, based on the fact that the base of the XTP would be farther in the case than RMR at the same COAL?
That sounds reasonable. However, you may be able to seat them longer than that anyway, depending on what fits in your particular guns(s). Do a plunk test to determine cartridge OAL and then go from there. Do you have a chronograph?Originally Posted by andrew j
When in doubt, I load long. As long as you can, and still maintaining neck tension, is best IMHO. Magazine depth/length/feeding, and bullet shape vs throat(s) in your chamber(s) are also considerations.
XTP's are an odd truncated cone shape, and the sharp shoulders will jam in throats if loaded very long. They often require very short OAL (compared to other bullets of the same caliber and weight) to avoid that. As I recall, suggested OAL in 9x19 with a 147gr XTP is only 1.10"...Which is dang short, but also might not be long enough in something like a CZ chamber (I stuck a 125gr TC shaped lead bullet in a CZ throat once, assuming the load that would feed in my Glock would work in the CZ was a mistake). I suspect the more rounded shape of the RMR bullets can be loaded a bit longer than XTP's. A "plunk test" is a good idea here. Using XTP data to start with, loading a bit longer OAL, and work up from there is a good plan, IMHO.
I looked on RMR's website and didn't see any 9mm bullets listed as "hybrids", just standard round-nose FMJs. If your bullets are something else, a picture or a link to a picture would be helpful. I'm going on the assumption that your bullets are the FMJs; if they're something different, ignore this.
Max OAL for 9x19 is 1.169". This OAL is only found with round-nose FMJs; the shapes of most hollowpoints require deeper seating. Data for FMJs usually shows OAL in the 1.12-1.15" ballpark. The shapes of RN-FMJs will be similar but not the same; some will be relatively long and tapering, others shorter and blunter. They'll require different OALs so they don't jam into the barrel's rifling (as noted above). How do you determine this? You use the "plunk test".
To do the plunk test, you fieldstrip the pistol and ensure the barrel's chamber is clean. Take a completed round and drop it in the chamber (where it'll make a "plunk" sound, hence the name) and press lightly on the base of the cartridge to ensure the cartridge is fully seated in the chamber. Then you turn the barrel muzzle up - the round should drop out. If it does, you're good to go. If it doesn't, first check the diameter of the round at the case mouth to ensure it's crimped correctly, then start seating the bullet deeper, going about .001" at a time until it does. If you want to cheat on this, just take a round of factory FMJ ammo that you know works in your gun and set your seating die to match it. That works almost all the time. You still need to do the plunk test to verify that it works with the bullet you're loading.
Good luck!
The cartridge should also spin freely in the chamber. (Not spinning freely usually indicates that either the case is just slightly out of round or the bullet is just barely catching on the transition from chamber to rifling.) My process for this is drop the cartridge in, spin it at least one full rotation, and then drop it out. If it fails at any point in that process, it's a reject.
To the OP: If you are loading for multiple guns, every barrel will be different, so it's beneficial to try them all - you should pretty quickly figure out which one has the shortest/tightest chamber, and you can then use that one to set OAL for future changes in components, and as a "case gauge" for doing quality control on the ammo you produce.
The reviews section of RMR has load data from other users:
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