Younggun is wrong - don't use jacketed data for plated bullets; use LEAD data for plated.
Plated bullets are softer and operate more like lead bullets. Using the jacketed bullet data can result in the loads being too "hot" and losing a lot of accuracy.
In any case, no bullet type should change the velocity sufficiently to cause you ejection problems. More likely you have an issue with the amount of powder or (possibly) with the amount of crimp on the bullet. (That can be a problem in semiautos.)
And keep in mind that speed is not equal to accuracy.
Younggun is wrong - don't use jacketed data for plated bullets; use LEAD data for plated.
Plated bullets are softer and operate more like lead bullets. Using the jacketed bullet data can result in the loads being too "hot" and losing a lot of accuracy.
In any case, no bullet type should change the velocity sufficiently to cause you ejection problems. More likely you have an issue with the amount of powder or (possibly) with the amount of crimp on the bullet. (That can be a problem in semiautos.)
O.K. Now I know what you're talking about, you mean "Rainier" bullets...like the mountain in the Pacific North West. Let's get some nomenclature straight here so I know what you're asking. So what's happening is the cartridge you're shooting doesn't drive the slide back with authority and the spent case simply falls onto your foot, correct?
But it is ejecting. Does the slide fail to pick up a new round and move forward into battery?
As always should add the caveat that you need to check this stuff yourself in multiple loading books or at least multiple online load charts. Never trust one book (printing errors happen, numbers get switched) and never trust one guy posting info on a forum. And of course work your load up from the bottom watching for pressure signs (very few exceptions to this rule such as doing subsonic rifle rounds like 300BLK where you want to start high and work down to consistent subsonic).
First, post your settings. What is your actual OAL and crimp?
Second, what manual are you using and what is the recommended settings. All manuals list an OAL, even if it is the max, 1.169" in this case.
Three, different types of bullets are different lengths. In general a JHP will be longer than a FMJ so at the same OAL the former will operate at a higher pressure due to reduced volume in the casing.
Even with a GDot Alliant lists up to 4.4 gr of bullseye. If you have nothing else, at your OAL at 1.130", your crimp at .378", primer depth at .003", and start at 3.8gr. And work up to 4.4. With a 124 you are not going to strip the plating and doom will not fall upon you.
This. You don't want to push plated bullets past what the manufacturer suggests. I think most plated say not to push them past 1200-1400 fps. Granted with 124gr 9mm I don't even think FMJ generally get pushed this fast (been a bit since I reloaded so I can't remember off the top of my head). Of course you have the double plated that can be pushed a bit harder but I don't think rainer does this with theirs (I always used Berry's before I got into casting). Also be light on the crimp you put on them. If you break the plating you can actually have the plating on the base separate and lodge in your barrel potentially causing a kaboom if you follow it up with another round. At the very least it can cause leading issues which is a PITA to get out (all copper chore boys wrapped around a well used bore brush works but it takes alot of elbow grease).