I agree with Lakota - I prefer the 125s. Try 'em both, and see what feeds best.
I had one 9 that would take 125s in round nose or conical, and another that will feed round nose all day, and choke half the time on the truncated cones.
My brothers gun shoots 147 most accurately so that is my reload for him. He has a couple of thousand rounds of bullets from 90 to 115 to 125 that need to be shot up and they all work, its just that his gun likes 147 for making tight groups. Thats my criteria, if his gun liked 115 better thats what I would load for him.
It depends on your pistol, they're all different. For my Beretta 92, the 147 grain gives best accuracy with groups half the size of the 125's or 115s. For my SIG, 125's work best. I get best results loading to velocities about 80-90% of the max listed in the Sierra and Hornady books.
My discussion here deals with accuracy rather than with throw-weight.
With my Glock 19, bullet weight seems to be less of a factor than profile. It seems to deliver the best accuracy with a bullet having a longer bearing surface. Bullets with a more gently-sloping ogive seem to do better than bullets with a more sharply-sloping one. Consequently, the lighter bullets seem to be less accurate because their reduced weight calls for a design providing less bearing surface. One of the bullets this gun likes best is the 130 gr. designed for the .38 Super.
There are often exceptions to rules, and the lighter weight conical bullets are the exception here. This is because even though they are shorter, the abruptly sloping profile increases bearing surface. For example, the (obsolete) 110 gr. Berry jacketed conical bullet (shaped kinda like a SWC) works very well.
One of the worst performers in my Glock is the bulk RP 115 gr. JHP, which has a very long ogive and short bearing surface.
My Star Model B sprays quite indiscriminately regardless of bullet weight.
I have several 9x19mm pistols. Each is different.
My Glock 19 likes 124 grain(I have hard cast and watch build up, will eventually change the barrel) it will digest 115 and 147 but does not perform as accurately with them.
My 92 likes 147 grain but will shoot all of them, the 147 is more reliable and accurate.
My P1 likes 115 grain FMJ, feeds them well and shoots them with reasonable accuracy.
I got into this mess because I needed a 92 to practice with (the government doesn't supply enough ammo to become proficient) then I got a 19 to take to ODS as a backup. The P1 was something I just wanted. Having said all this....I love my M1911A1 most of all.
When it comes to shooting lead in a 9mm, I find heavier to be a bit of an advantage most of the time. The reason for that is that it's easier to generate recoil/cycling energy at velocities that minimize leading. Cost is usually so similar as not to be a problem.
Ogive configuration is always a try it and see sorta thing with any given weapon.
I have two 9mms that I shoot cast bullets in, a HiPower and a Star Starfire Plus. With 124 grains bullets I get the best accuracy abd this is also the weight of the bullets that I use for my carry pistol. I tuned the load for my HiPower and shoot almost as well in the Star.
At the range, I shoot what I carry, then there are no suprises. My load is 4.1 grains of WW231.
I do not shoot lead, or light copper plated or copper washed bullets in any of my Glocks, the barrel geometry is all wrong for cast bullets, so I don't want to use that may casue major problems.
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