Subsonic loads for .308 and 5.56

[paramil]

Anyone using IMR 4064 for subsonic loads in .308 or H335 for subsonic loads in 5.56? If so I would be interested in what your pet load is. If not then what powder do you find best for these applications?

And if I am correct (sanity check) to obtain subsonic speed your looking at staying at or under 1,100 feet per second? Thanks guys.

 

[mtrmn]

Trail Boss---around 10 gr for 308 and 4.5 gr for 223.
POI about a foot low at 100 yds.

 

[SMM123]

Trail Boss---around 10 gr for 308 and 4.5 gr for 223.
POI about a foot low at 100 yds.

Or he could simply go the way of a 300 AAC Blackout and be done with it.

 

[biffj]

with the full sized 308 and .223 loads you don't just pick a powder and decide to load subsonic with it. You have way too much case capacity and you will need a powder that fills the case at least 50% in order to avoid some destructive booms and also to help improve consistent ignition. For the .223 you're better off using a .22LR as its much simpler than trying to get a 50gr bullet out of that long barrel subsonic. You'll probably have much better accuracy too. For the .308 you are better off with the 300 blackout as it gives you a choice of powders that will allow you to come up with something accurate instead of something that just shoots. The other possibility is to make up cartridge cases with reduced capacity by either machining them from bar stock or filling existing cases with epoxy or lead or something and then making a smaller powder chamber. Having 10gr of powder rattling around in a case with a capacity of 50grs makes it tough to keep things consistent.

So to answer the original posters question: no I don't know of anyone (living) who is using 4064 for subsonic loading in either .223 or .308. Subsonic loads need to be under 1100fps and in reality need to be in the 1050fps range due to acceleration of airflow over the curve of the bullet which will cause local sonic booms if you shoot at 1100fps. In addition the speed of sound varies with temp so running at 1100 which is the speed of sound at sea level and standard temp and pressure (59 deg F and 14.7 psi) may be supersonic at lower temps.

Frank

 

[mtrmn]

What he said^^^^^

After much testing and tinkering, I decided I had no PRACTICAL use for subs in calibers meant for supersonic use. The high performance expanding hunting bullets will NOT be high performance at 1050fps. Even with normally exploding varmint bullets, many of them could probably be re-used after shooting them into water. The only change was rifling marks on the jacket. There ARE bullets specially designed to perform at sub-velocity but are pretty costly. I'll keep the terminal performance of normal velocity ammo and put up with the sonic crack.

The supersonic crack comes from the bullet, not the gun, and follows the bullet downrange. Therefore the shooter's location is much harder to pinpoint because the crack drowns out any other noises the gun makes in most circumstances. When a supersonic bullet passes your position downrange, the sound is much like someone standing nearby and shooting a 22LR. The sound comes from the point of travel nearest your position and drowns out any noises from the gun.

In my use, subs are good for shits and grins while impressing your friends with your cool silencer. Many other shooters are much more serious with sub use than I am. YMMV

 

[paramil]

Well I will keep with my current calibers. I understand there are better options for devoted subsonic loads out there, however 5.56 and 308 are what I have and what I shoot. So if there are particular powders that work better with these calibers for subsonic loads then I am all ears; but changing weapons just for subsonic performance not an option at this point.

 

[b6graham]

trailboss

 

[paramil]

OK, in what powder weight and for what caliber?

trailboss

 

[b6graham]

i run 11gr in 308. seated to mag length in an AI AE MkIII 20"

edit: 175 SMK. same POI at 100y

 

[Sapper524]

i run 11gr in 308. seated to mag length in an AI AE MkIII 20"

I run 12g or trailboss under 220g round nose ... 4 mil low at 100 - 1.5 - 2 MOA accuracy at 100 out of my 18 inch rem 700. Silly quiet with my SAS Ti can

 

[SharpsNitro]

OK, in what powder weight and for what caliber?

There are other threads on this that you can find using the Search function. That said, 10gr of a Trail Boss under the 200gr Lapua subsonic bullet has worked well for me (1:8" twist).