Sub sonic loads for 300 Win Mag

[azrogermoore]

I own a suppressor for my McMillan Tac 300 and would like to load some sub-sonic rounds to see how quiet it could get. Does anyone have any recipes for sub-sonic loads for the 300 Win mag? I normally shoot 180 grain Barnes bulllets.

 

[86alaskan]

you'd want to use as heavy bullets as possible, then a very small amount of powder. I think it may be kinda hard with a 300WM due to the case capacity. if you could find a good powder, you'd need a filler to keep that powder in a good spot for reliable ignition. I know in the blackout you can get wild velocity swings just based on powder position in the case alone. also, a sub 30cal is a sub 30cal, it'll most likely be just as quiet as a blackout, just with way more work involved.

 

[Trnelson]

Not the easiest way to do a sub-sonic 30 cal...it's next a kin to de-tuning a Ferrari to pull a trailer. I'll assume you have a 10 twist barrel. If that is indeed the case you will be limited to 220g and lighter to be able to stabilize. Use the heaviest bullet you can stabilize as it will help keep the SD as low as possible. Don't even think about trying to use the 180g bullets you have on hand. The SD will be ridiculous and will get worse as you try to slow them down to sub-sonic. Outlaw State Bullets makes several .308" low velocity expanding bullets. I've taken a few deer with their 250g out of my 300blk and had no problem getting MOA accuracy and mouse-fart quiet.
As far as powder goes, this is the tricky part with the large case volume of a 300 win mag. IF I was going to try to attempt this I would start at 23g with trailboss and work down or A-5744 at 27g and work down slowly. Use magnum primers and expect to see SD of 75fps. For the love of God work with a chronograph so you know exactly where you are at, STOP when you get a subsonic load. Don't be tempted to try to get to 1,000 fps, when 1050 is sub-sonic. The chances of sticking a bullet in the barrel goes up dramatically the slower you try to go. STOP if you encounter ANY sign of a hang fire, odd sounding or delayed ignition. Lastly, look down the bore after every shot during load development to be sure the bullet actually left the barrel, even if the chronograph registers a velocity.
Lastly, buy a Ruger American in 300blk for $400 and enjoy using that awesome 300 win mag how it was meant to be used.

 

[dsculley]

With an AR chambered for 300Blk and shot subsonic, you can hear the slide function, you can hear the bullet strike an object 100 ft away, you don't hear a shot. I would assume the same would be true if you can get the 300 win mag subsonic. The 300 win mag has a lot of case capacity that will have to be addressed. I agree with Trnelson, if you want a subsonic round then get one that was designed to be used subsonic. The possibility for accidental damage to the rifle and the shooter is too much for me to want to try it.

The 300blk can be a fun round too.

 

[Deleted member 46119]

There are ways. I have done it with very large cartridges.

I don't like how it will work in a 300WM for sub sonic. It's "odd".

If you were willing to go "low velocity", 1300 to 1600fps that is easy. The noise signature of very very low. With a suppressor no hearing protection required.

I am wondering though, other than the because you can factor, why do you want something that big to go slow?

 

[azrogermoore]

Thanks everyone! My ONLY purpose to load subsonic is because I already own the suppressor for this rifle. My interest is purely curiosity and to try to protect what little hearing I have left.

I hand load for all my rifles and am not thinking of hunting etc.

I have a chronograph and will load down slowly and post what I found.

THANKS AGAIN!

 

[Deleted member 46119]

As I understand it, normal firearms will be about 150db. Loud enough to damage hearing with one single exposure. The same firearm with a suppressor would be 120db. A level that would take a great deal of sustained exposure to cause hearing loss.

My numbers may not be perfect. I was going by memory and a couple web sites.

So

If you want to be as silent as possible with a suppressor, the subsonic ballistics, quiet powder charge and a suppressor will pretty much get you to the point where the mechanics of the firearm are the noise.

I build a 10/22 without a suppressor but with a long barrel that was in that realm. The loudest thing was the bolt moving back into battery. The rear bolt buffer was polymer so it made no noise.

 

[Trnelson]

I own a suppressor for my McMillan Tac 300 and would like to load some sub-sonic rounds to see how quiet it could get. Does anyone have any recipes for sub-sonic loads for the 300 Win mag? I normally shoot 180 grain Barnes bulllets.

Silly follow-up that I should have included in my first post.....
What suppressor are you running on your rifle? Is it rated to be able to handle a 300 win mag? A quick Google search or phone call to the manufacturer will confirm that. Assuming that it is capable, you can shoot your regular 180g Barnes load through it. As jfseaman noted, you will likely not 'need' hearing protection with even that load. You likely know about this as well, but I'll include it for the sake of posterity. Expect a POI change though b/c the suppressor totally changes your barrel harmonic, sometimes a lot. In my 264 win mag the poi changes ~6MOA at 100 between suppressed and Unsuppressed with my Specwar 7.62 muffler... Velocity also changes about 35fps faster when I'm running the can on that rifle. Have fun!

 

[RckyMtnRutt]

So will this actually work? Like a dumb A i bought these thinking I could load down a 300 win mag load to spit these out. Just wondering if I need to get rid of them and ditch the subsonic 300 win load Idea....honestly pretty quiet how it is.

 

[david g ranes]

N

I own a suppressor for my McMillan Tac 300 and would like to load some sub-sonic rounds to see how quiet it could get. Does anyone have any recipes for sub-sonic loads for the 300 Win mag? I normally shoot 180 grain Barnes bulllets.

New a guy several years ago from Mississippi shooting trail boss in his 308 worked really well don't know what it would do for you in a 300 win mag. David

 

[JFriesen]

I've been waiting for trailboss to show back up for my 308. That's part of the reason I bought a bolt 308. Wouldn't dream of trying sub loads in 06 or 300. But maybe it's possible.

 

[L.Sherm]

If you wanna shoot subsonic buy another gun, you ever heard of detonation, it can be not a good experience.

 

[Old Rooster]

A friend had an old 45-70 single shot H&R and got tired of it kicking his butt so he downloaded it big time and shot it and it exploded.
Thats what L.Sherm is talking about.Some call it detonation and some call it flash over.
He bought a new H&R and downloaded it but filled the top of the case with cornmeal.The only problem was when he shot that rifle it smelled like someone cooking cornbread.
Never load too low,I saw the rifle that exploded and the worst was everything around him got peppered with steel fragments,glad I was not there that day.

 

[ducky]

Like others said case of Trail Boss maybe? Looks like you can get 18 grains of TB in the case with a 150 grain, but you're still supersonic.

https://www.google.com/url?sa=t&source=web&rct=j&url=https://imrpowder.com/wp-content/uploads/2016/11/trail-boss-reduced-loads-r_p.pdf&ved=2ahUKEwiYuqiYtpbyAhVrAp0JHeuRA3YQFnoECAoQAg&usg=AOvVaw36_OGGZV785lkqWrnoGv37