Subsonic Reloading

I have zero experience with reloading but I haven’t been able to find subsonic ammo for 308 and 223/556. So, I have decided that reloading is probably my best bet and will be cheaper in the long run.

Does anyone have any suggestions on where to start? I’d hate to go out and spend a bunch of money on the wrong gear. I’m specifically interested in reloading subsonic rounds. If there is no real difference between load supersonic and subsonic, I’d like to know that as well.

I’m just brand new at it and any advice is welcome.


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5.56 loads of 69 grain bullets with reduced amount of gun powder. I run 24.6 grains of powder for optimal loads. This runs at 1117 energy foot lbs. If I reduce the powder to 22.6 grains it will lower it to 882 energy foot lbs. A good loading manual can guide you in this. An 80 grain bullet with H-4895 gun powder at 20.1 grains of powder will have 940 energy foot lbs. while raising the load of powder to 23.1 will bring the energy foot lbs. to 1201.
I have loaded a black powder pistol once to minimal load and you could actually watch the lead fly to the target.


Subsonic ammunition is ammunition designed to operate at speeds below the speed of sound , which at standard conditions is 343.2 m/s (1,126 ft/s ).


I’ve noticed this effect is especially pronounced at night with a IR scope. My PCP throws lead in the upper 800s FPS. You can’t really see it during the day but the IR light bouncing off the lead at night combined with the slow speeds makes for some pretty entertaining shooting.


Travis, to your point–there is no difference between reloading supersonic and subsonic ammo. You’re just aiming to build a slower load; hence, less powder.
Opposite of usual reloading–you don’t work your way up to a load–you work your way down. Make sense?


There is quite a bit of research that has to be done to build effective subsonic ammo for high pressure rifle cartridges.

First and fore most will be boolit selection, you will obviously want the heaviest you can get that when loaded will fit in the magazine but not extent TOO far down into the powder column.

Second will be powder selection as you will need a slower Magnum type powder not just the regular powder with a reduced charge weight. There is an effect that can occur when there is too little powder in the case (the name of it escapes me at the moment it may be “Double Boom”). The theory of how a powder works is that the majority of powder is lit by the primer from the rear and forms a molten “slug” that compresses the rest of the powder causing it to ignite almost homogeneously to force the boolit out with the greatest efficiency. When there is too little powder the “slug” can actually "rebound " and the primer becomes the “boolit” obviously fire from the back end of a cartridge is not preferred.

The other factor will be if you are running suppressed as that changes EVERYthing.

Speaking of suppressed and subsonic. The cartridge will still go BANG but being subsonic it will not go “Crack” in a regular barrel, with a suppressor you will still get noise but not nearly as much even if supersonic.

The other issue with subsonic rounds is range and ballistic profile. Big boolits going slow drop like rocks and sometimes depending on the platform are not even viable for 100 yard shooting. Most folks loading subsonic stay at around 1050 fps to allow for the length and breadth of atmospherics as well as the amount of trash that remains in the barrel. Subsonic and suppressed weapons are notoriously filthy.

Subsonic ammo due to the popularity of suppressors has become more main stream but I would have at least 2 - 3 verified recopies of platforms similar to your prior to putting them together. TAKE NOTE This is the ONLY time I will EVER recommend using the hottest load as a starting point and working down.

I’ve been reloading for more than 30 years and have played that game as well as the other end of the spectrum and I would be happy to assist you in your journey and putting together your gear.




Wow, Thank you! I’m probably going to reach out to you in the future at some point.

Tracis25, Many of the people here will help in any way possible. While I donot have decades of reloading experience, my loads do OK.
I would suggest a reloading mentor someone that can talk as well as show you what is going on. Check any of your local Gun Stores and ask about reloading and people in the area that do. You can read all of the books you want and still not know what to do to take care of a stuck case.
If you decide to invest in reloading tools, I would suggest starting with a single stage reloading press, along with the scales and other pieces. Top on the list is a reloading manual, buy several. Check local classified ads for equipment. I would strongly urge you not to buy reloaded ammo from someone you do not know.
I will also say if question come up do not hesistate to ask. Hope I can help.


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Awesome! Thank you so much! I will likely have questions for you in the future, I appreciate the assistance!