Thread: .300 BLK or something else

I have been toying with the idea of getting a dedicated subsonic barrel for my blaser.
I am leaning toward the .300 BLK out as I already have a .223 barrel and mag.

Not having any experience with subsonic centrefires apart from subsonic 7.62 (was useless) in the military I am thinking this may be the easiest caliber for me, with a lot of load data and info out there.

I have a few stations I cull animals on and if I can stretch it to 150 yrds or so I think it will be very useful.
Are there any dedicated optics with reticle for the .300 out there.
Will it kill large bodied stags out to 150 yrds.

I hear powder favoured for the .300 can be hard to get etc.
Is there a better subsonic calibre that has better and more available components?


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No experience with blackout, but a bit of experience with 30cal subsonic.
yes it will kill out to 150 but expect delayed killing, in fact expect delayed killing unless you hit the cns.
There are a few projectiles out there now that improve subsonic terminal performace but it is still subsonic.

The 300 AAC is a great sub round, very quiet, but you need to treat it like a .22 if shooting animals.

If you dial you shouldn't have trouble out to 150 but as mentioned you need to hit the CNS properly.

The trajectory is very rainbow like.

Bolt guns aren't a problem with powder, the ARs are a little difficult unless you have a sub specific upper.

The sub specific projectiles look good but they aren't that easy to get.

Plenty of brass & Hornady factory rounds are available

I drunk deep from the 300blk coolaid bottle, and wish I hadn't, the new bullets help a lot but I wish I hadn't sold .45apc and .44mag rifles to do it.
300blk is a lot easier to hit with at range than ether of them but as has been said I can be a slow killer.

Bushnall make a 300blk scope but I found the drops a bit out and ended up with a Leopold custom shop retical with my actual drops in it.

Are they easy to get accurate enough to hit neck or brain?
Would cast bullets, if accurate work in the sense of being more frangable?

If they perform to 100 m I will be more than happy.
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I liken subsonic body shots to bow hunting but with a bit more effective range, up close it is possible to get bang flops on hillar zone shots but it is not the norm.

Replace "bang" with "ploof

Cast projectiles are probably best but with a big meplat. The bigger the cal the better (more mass to penetrate and energy to transfer), trajectory would be the same as for a .22 sub. 44 mag or long colt would do, 444 marlin or 45/70 with a 400 grain plus slug would be perfect. Bison are bigger than stags and look what happened there.

With the heaver smk and a rangefinder combined with dialling I found that 300blk is very accurate at any distance, and that is the main non AR advantage to the caliber.
I had less luck with my cast pills but a better caster could probably improve on that.

I settled for a non dialable scope set for 150gn suppers and 240 subs but if I was doing it again the subs would be the lehighs as they kill better in my experience.
I found dialling to be to slow at the close ranges that I would use the subs as I have mostly used it on goats

Originally Posted by Marty Henry

Cast projectiles are probably best but with a big meplat. The bigger the cal the better (more mass to penetrate and energy to transfer), trajectory would be the same as for a .22 sub. 44 mag or long colt would do, 444 marlin or 45/70 with a 400 grain plus slug would be perfect.

I prefer the 450 BM over the 300 AAC for that reason, the downside is they are harder to keep quite.

I have got some 235gr Cast bullets to try out for sub loads. Might be my mission for the weekend.

Here is my view after experiencing with one 300 whisper, one 300 blackout and 2 308, and 1 458 socom:
Yes the whisper/ black out can be very accurate even at 200m with match bullets like Smk or a-max.
But the adverse effect is that they tend to pencil straight through the animal unless they touch a bone at an angle and then tumble and make a cut. Then the death is a bit quicker specialy if you have touched a vital point or cns.
Powder choices are reasonably wide.

With 308 and 170gr FP hornady you get very similar performances, and the accuracy can be very good, like under 1 moa at 100m.
I have tried opening the tip and making an hollow point, it seems to kill marginally better but the again vital point or cns need to be hit!

when a mate and I tried 150 cast bullet HP ,now we got something really interesting:
First they expend and fragment making a wound the size of a 1$ To 2$ coin and they still have enough punch to go through 2 goats side by side at 100. We have repeated the experience twice!
They kill faster than the above jacketed bullet I mentioned earlier. And they stabilise in a 1 in 10 twist barrel( I need to try them in a 1 in 12 to see how they go).
I have not tried the Leigh but they seem promising.

As for the 458 socom they punch straight through and make a bigger hole. But again,like for the 308, the jacketed bullet DO NOT Expand!
There fore the animal can still run away if not touched in a vital point or cns.

So at this stage I would advise you as follow:
First, there is not much need to go above 150gr in 30 cal , because the projectile zip through and excess energy is waisted outside the animal and sometime in some very spectacular ricochets: watch out the background of your target!
If you are going to use cast, then a 1 in 10 twist 308 will do the job and I am pretty sure that the 1 in 12" will stabilise the cast as well.
And they will /should shoot more accurately than in 1 in 8 or 7 twist.( we are talking 100 to 150 m distance here not 50 yards)



The 300 blackout/ whisper would be interesting with Leigh bullets , the twist is perfect for those specialised bullets but I have not tried them yet.

Going bigger: in a near future I intend to build and to shoot a 38/ 357 silenced rifle with 158 fr Xtp and see how they perform. I will try some cast as well.
Same thing with a 44 mag. ( ruger 77/44)I also have to try some cast into the socom.
Lots of projects, not enough time!

I although guess that if you are going the blaser way a 308 factory barrel ( second hand?)would be easier go acquire than a300 blackout.
You can cut it down to 16".
I although suggest that whatever way you go, you run a good number of jacketed bullets with good cleaning procedures to break in the barrel properly before shooting cast bullets.

Pretty much all the comments from the other guys are true, just don't get to carried away by what the ( Internet ?)merchant is trying to tell (sell?) you.
Pm me if you have further questions.

Also, the bigger the hole the bigger the noise!
And the heavier the bullet in a certain caliber, the more powder you need to push it out and therefore the more noise It makes.
That is although why I tend to favour a150 gr in 30 cal.

All good comments!

I have been playing with subs for about 18 years and tried: 7.62x39, .308, .300WM, 30-06, .300 AAC and for something bigger .338WM. All these calibres can work well for subsonics on essentially the same powder charge of 8-10 grains of shot gun powder. All will shoot quietly with the right can. The only issue is slow twist barrels won't stabilize heavy projectiles like the Lee 210 grain cast. These are my favorite sub-sonic cast projectile and shoot awesomely from my 1:8 twist .300AAC. All barrels i have seen in this caliber have the required twist where many other .30cal barrels don't, another advantage of this sub sonic specific caliber (apart from cycling ARs).

A bolt gun in .308 with a fast twist barrel would give you a good subs and more powerful full power loads. Yes bigger cases such as the magnums seem silly with 10 grains of Shot gun powder but a little kaypock filler will hold it against the flash hole and seemed to work fine.

Yes cast bluets kill better on non head/neck shots ie chest/heart BUT are generally not as accurate.

190g launched@ 900fps from 1in11 twist into stack of well soaked newspapers at 40 yards.

Originally Posted by veitnamcam

190g launched@ 900fps from 1in11 twist into stack of well soaked newspapers at 40 yards.

haha did you give the neighbors a fright?

na my section is not 40y long lol