Anyone done this?

I’ve set my sights on my next firearm purchase, and I’m going to get a 9mm carbine. Next step would be to get a suppressor for it. That will take a while.

I have an over abundance of 124 gr RN FMJ. I would like to continue to us them, if possible. They work well with my current 9mm pistols.

If not, I can always move up to 147gr.

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Reg. Magnum wants/Rossi wallet

Best way to find out if they're sub sonic would be to chronograph them.
Rounds that may be sub sonic in a pistol may not be that in a longer barrel.
I have a AR-9 that I built that is suppressed, if your pushing 1000 to 1050fps in a pistol they will most likely exceeded 1100 in a carbine.
You can most certainly load 124s below 1100 you'll just have to work them up.

The speed of sound is a pretty small window. To get enough energy to accomplish more than paper punching, you will have to up the weight! 147 is the military standard for sub-sonic 9mm since the Vietnam War. Accurate powder also gave sub sonic data using .357 158 grain soft points in 9mm. When I started making sub sonic loads for my MAC-10, the heaviest projectile one the open market was Sierra's 130 FMJ Tournament Master. I used WW231 with great results. For 147 & 158 grain bullets AA #2, #5, & #9 all worked pretty well. With the 130gr/WW231 load I could keep 5-6 round bursts in 3 to 4 inch groups at 50 yards fired from the shoulder stock. Without using a stock, full-auto groups are much bigger than #4 Buckshot patterns at the same distance! The heavier bullets add a little more recoil (still not much!), but always seemed to group better in carbines and sub-guns (at least for me.)

Due to the lack of energy, I quit the entire 9mm program 25 years ago and went with 45, but still not much knockdown at 50 yards. So I gave up on sub-sonic and use 223 & 308 and put up with the sonic crack. A 223 from a silenced AR-15 sounds like a high velocity 22 LR (un-silenced). Without full auto the neighbors thought I was plinking with a 22!

I have come back to 9mm for CCW, but not with a silencer. The funny thing was Before Ohio had CCW, my State Fire Marshal's "Dangerous Ordinance" permit, allowed me to CCW the machine gun and silencer!
For CCW 9mm I like the 147 grain factory ammo, and it is sub-sonic (at least in a handgun, don't know about a carbine).

Hope you figure out what you want, without spending too much time and money!

Ivan

Am preferring the 147 grainers for suppressed. The subsonic load is at the velocity they were designed for (jhp's), and the increase in velocity from a carbine has been minimal, evidenced by staying subsonic. Can use same loading for fmj and jhp's. 147 grainers leave little room for powder, and do not substantially increase in velocity like a 124 grain load.

Certainly you could handload 124's to stay subsonic in pistol and rifle, and using quicker powders may give very slight reduction in noise. However am proponent of reducing the number of "special" loads as I get older.

No problems with a short 3.5" getting sub-sonic loads...
it is a little harder with a longer 5" barrel but can be done with a
124gr or heavier bullet with the right powders.
996 to 819fps depending on bullet weights.

With the longer rifle barrel you will need to really be careful on the
loads and bullets that you will choose, if you truly want real sub-sonic loads.

Federal list 1030fps as their S/S loading.
Wilson has their Target 124gr at 1075fps from a 5" barrel.
Better safe than sorry..........

Take care.

PS;
as a added note on Sub-Sonic loads...
When shooting my X-Lite target loads, I know when I have arrived, when

while wearing ear muffs, I can now hear the pistol "Working"
as the slide is coming back on recoil and the "Metallic" sounds
that I can now hear, that were covered before by muzzle blast.

Always look for a "New hole" or flying dirt............
before pulling that trigger, again !!

Another GOOD reason to have use of a chrony.