• Watch Out for Scammers!

    We've now added a color code for all accounts. Orange accounts are new members, Blue are full members, and Green are Supporters. If you get a message about a sale from an orange account, make sure you pay attention before sending any money!

300 Blackout Bolt Gun or 308 Subsonic

T

treillw

Private
Full Member
Minuteman
Mar 3, 2017
659
84
Have two cans in jail (TBAC 5 & 9). New to all this. Thinking it would be fun to get a 300 blackout to play with.

I've been thinking, could you just load a 308 subsonic and essentially have it be the same thing as a 300 blackout with the option to crank up the horsepower if you wanted to? Would case capacity/powder volume be an issue? Any good powders for doing this?

What are some cool 300 blackout bolt guns to put a can on? The most common one I see is a ruger american.
 
I'm very interested in this as well. I figured you couldn't do a 308 sub and then load super because of the speed difference it would require completely different twist rates but I'm by no means knowledgeable on this...
 
In a 308, trailboss is where it's at! A .308 bullet at subsonic speeds is subsonic whether from a 308/300bo. I used to load subs for 308 but after a while I just focused on the black. Accuracy is OK but not excellent. The drop on either caliber is a killer. Ur right tho, if u want to turn it up, you have alot more case capacity for options.
 
  • Like
Reactions: HillBilly n TX, faultball, Vargmat and 1 other person
Good point on the twist. I hadn't thought of that variable. According to this, it looks like you could get some 185 grain bullets stable at 1100 fps with a 10 twist barrel. 10 twist is what I use to crank 215 grainers out with my 300 win.... Also what a 308 ruger american comes in.

bergerbullets.com

Twist Rate Stability Calculator

Our newly updated Twist Rate Stability Calculator not only tells you what your SG is, but it also lets you know if you are reaching your optimized BC.
bergerbullets.com bergerbullets.com
 
10ring1 said:
In a 308, trailboss is where it's at! A .308 bullet at subsonic speeds is subsonic whether from a 308/300bo. I used to load subs for 308 but after a while I just focused on the black. Accuracy is OK but not excellent. The drop on either caliber is a killer. Ur right tho, if u want to turn it up, you have alot more case capacity for options.
Click to expand...

The trailboss powder fills up the case enough, so you don't get any misfires? If a 308 will work the same as a 300 blackout, how in the world do they sell the 300 blackout??
 
  • Like
Reactions: 10ring1
treillw said:
The trailboss powder fills up the case enough, so you don't get any misfires? If a 308 will work the same as a 300 blackout, how in the world do they sell the 300 blackout??
Click to expand...
It shines in the small frame ARs. Bolt guns are kind of a wash if you’re handloading. Big plus for 300BO is you can buy subsonic factory ammo fairly easily.
 
  • Like
Reactions: 10ring1, Dan M and treillw
When I was loading subs it was 10.2 grains of trail boss and a 208 AMAX. 1/10 twist krieger. It was fun. But I found myself launching a few and then going right back to supers.
 
  • Like
Reactions: lash and 10ring1
I just changed my 300bo bolt gun to a 223. Im sticking to the cartridge in ar only because it has a bit more oomf than 223 out of a small frame ar for close range thermal hunting, especially in its sbr state. In a bolt gun I would rather a 308 any day. The blackout in a bolt gun is a novelty. 308 with trail boss is equal to a 300, 308 with real powder is superior.
 
  • Like
Reactions: lash and 10ring1
I went .308 route. Have a 16.5" barrel on my Mausingfield. Just getting around to testing it out, have about 70 rounds loaded up with 10.0gr. of Trailboss. For me it was a mix of both knowing I can gas up to full .308 power and not wanting to deal with .223 class cartridges in a normal short action (especially w/the mauser claw). I'm sure many can get it to work but I'm lazy like that.

Initial results showed about 43fps ES, but I had similar spreads in a .300 B/O bolt gun (Ruger American). Putting a crimp on the 300 B/O tightened spreads into the teens, and tomorrow I'll see if the same holds true for the .308 subs w/trailboss. I will agree, it's fun for a bit then you hit the walls of the limitations of the low MV very quickly. There's also the pain of rezeroing between subs & supers. The subs impact about 4.5 mils low @ 100yd compared to the supersonic stuff.

Not the end of the world, but the limitations are greater. FWIW, Hornady 4dof seems to excel with subs over other ballistic calculators. I shot some 178gr HPBT's a while back subsonic. Zeroed at 50yd and went straight to 300yd with a 1st round hit on a 6" plate. I was extremely impressed, 2-3 other calculators had me up to 2 mils off.
 
  • Like
Reactions: lash and Aceteck
FCS said:
Honestly, if you want subsonic do a 300 BO for that and us 30-06 for launching the heavier, super high BC bullets.
Can you do both? Yes. However, subs from -06 is a compromise at best IMHO.
Rem 700 in 300BO works REALLY well and is plenty inexpensive.
View attachment 7093421
Factory 700 AAC-SD, 16” bbl, TBAC 30-P1, 208 Amax subsonic, 5 rds @ 100 & movie quiet.
Click to expand...

I've done 308 with Trailboss and 178 Amax / 175 SMK, is too dirty and sooty for my liking.
Rem 700 AAC-SD or Ruger American in 300 BO is plenty cheap, has a 7 twist barrel so you can shoot heavies accurately.
When shooting paper with the above, get asked if it is an airsoft.
 
Last edited:
300 BLK bolt gun with Unique or Bullseye powder is about as clean fun as you can have. I had better luck with 170 +/- gr bullets for subsonics with good accuracy but it could have been just my gun didn’t like the real heavies.
 
Does anyone load up the 6.5 creedmoor subsonic? I already have one of those... why buy a 308 to do essentially the same thing I should be able to do with my creedmoor?
 
I've thought to try it with 160gr round noses but never got around to it. Might give 'er a shot in the coming weeks.
 
Anybody here run the Discreet Ballistics subsonic 300 bo or 308? Been wanting to try it but haven't got around to ordering any.
 
mdonnr said:
300 BLK bolt gun with Unique or Bullseye powder is about as clean fun as you can have. I had better luck with 170 +/- gr bullets for subsonics with good accuracy but it could have been just my gun didn’t like the real heavies.
Click to expand...


^^ This.

Super quiet load, clean, and fairly accurate out of my Ruger. Here in the NE, I rarely get to a range with over 500 yds. so the .308 is kind of a waste. Sub blackout is fun and cheap once you have components and have a load worked up.
 
Depends.... Only reason I would do 300 blk is if I was shooting it in a ar platform. In a bolt gun it's kinda pointless imo. 308 subonics are easy peasy to load up. 10-12 grains of trailboss depending on bullet and elevation and done. I have slung thousands of 308 subsonic downrange with trailboss. If you know subs will be the main ammo shoot through it, do a 1/8 twist 308 or 1/9. You who still need able to shoot super sonic 308 np and will be able to fully stabilize any 200+ heavy pill np from a 16" tube
 
I shoot a few subs from 12 & 10 twist bolts. I have no issue to 600yds w/ either, (one 16.5" the other 22")throwing 193's or 217grs cast loads. Red dot is my main powder of choice but 700X, bullseye, clays an a few others work will.

Bullet Nose design matters more than twist.
 
I have never been able to stabilize 220s or 230s from a 16" 1/10...I can from a 1/8
 
You have other issues then. I've shot 250gr round noses in a 10 twist 16.5" tube w/o issue. The cost do to the amount of subs I shoot forces me to cast my own as I shoot about 25 subs for every high speed anymore. The Lyman mold # 311284V (210gr) will throw a 217gr ready to load pure wheel weight, lead bullet an it gets to 600yds point on when driven via 7.8 gr's of Red Dot, lite via a WLR primer. Mv is 1085 from my 16.5" factory tube.
 
Husky - jacketed 220s and 230 or a cast lead bullet?

GF14E2 spot on that nose profile, bullet design is determining variable.
 
Jacked I don't mold my own bullets.

With a 1/8 I can shoot anything. Suppressed or unsuppressed groups are great.


With a 1/10 I couldn't stabilize everything.
 
  • Like
Reactions: Maxduty
8s have been questionable for me, 7s better with 208 Amax / 220 SMK / 240 SMK.
10s marginal with 175 SMK / 178 Amax.

Cast lead bullets are significantly easy to make shoot well due to bullet shape.
IF you cast or can find cast bullets.
 
Huskydriver said:
Jacked I don't mold my own bullets.

With a 1/8 I can shoot anything. Suppressed or unsuppressed groups are great.


With a 1/10 I couldn't stabilize everything.
Click to expand...
My old 22" 12 twist would stabilize a 175 SMK to about 135yds, then they went end of end, but at 100yds they were .25moa groups. A 190smk grouped just as good to 100 but at 110yards they went end over end, really funny to watch to 250yds. The issue is more nose design than twist. A 200gr game king will get to 600yds in a 12 twist nose on but, not with only 10-11 grs of TB as there is to much extra weight an friction. When doing jacketed or cast subs you have to run them over a cronny to get to the target speed, as the slower they leave the less RPM they have an if they are going to slow even a round nose will have issue. I target all mine to 1080-1085, that way in my A/O even in almost the worst cold we get they will not go s/sonic. I do have loads that are good to -20*F but I've never seen those temps here, but I still carry them/with their card during winter just in case it goes to shit then.
 
The blackout shines in a 10" barreled ar to thump stuff in close with 220's.

Anything else might as well go to the 308 unless you need to run a mini action.
 
stello1001 said:
I'm very interested in this as well. I figured you couldn't do a 308 sub and then load super because of the speed difference it would require completely different twist rates but I'm by no means knowledgeable on this...
Click to expand...
Twist isn't case capacity dependent. All it cares about is speed and bullet.
 
And of course barrel length...realized some might not know that...however thats back around to speed.
 
Yep. Didn't read the whole thread...just wanted to clarify because some of the information out there is pretty screwed regarding 300 Blackout.
 
CJS-6.5 said:
Yep. Didn't read the whole thread...just wanted to clarify because some of the information out there is pretty screwed regarding 300 Blackout.
Click to expand...

Haha yeah. I just wasn't sure if one specific twist would work for two different proposes. Shooting suppressed at really slow speeds and shooting full power at high speeds. It seems many are having good success doing both with one specific barrel/twist...
 
stello1001 said:
Haha yeah. I just wasn't sure if one specific twist would work for two different proposes. Shooting suppressed at really slow speeds and shooting full power at high speeds. It seems many are having good success doing both with one specific barrel/twist...
Click to expand...
I read you. And it's TRUE. More in depth the speed/bullet combo is pressure related which does allow a twist such as 1:10 to work for big and slow and small and fast. The correlation seems to be with time of effect. So the longer bullet needs more spin but the time of travel through the rifling seems to affect it. So longer and slower can work with shorter and faster because the bearing surfaces are "seeing" the correct results.
 
  • Like
Reactions: stello1001
Within reason of course. And every bullet is different.
 
I use 178s - 208s in this...


Semi 300BLK, but same 30 cal bullets.
I would think the 308 case would have too much capacity.
20190507_205608.jpg
 
Last edited:
treillw said:
Have two cans in jail (TBAC 5 & 9). New to all this. Thinking it would be fun to get a 300 blackout to play with.

I've been thinking, could you just load a 308 subsonic and essentially have it be the same thing as a 300 blackout with the option to crank up the horsepower if you wanted to? Would case capacity/powder volume be an issue? Any good powders for doing this?

What are some cool 300 blackout bolt guns to put a can on? The most common one I see is a ruger american.
Click to expand...
It's case capacity, with barrel twist rate as secondary consideration. Case volume of a 300 BLK is 24.3 gr of water vs 308 56 gr. Same bullet means the 300 BLK will have much higher fill proportion than the 308. Higher fill means more consistent ignition and powder burn. As for twist rate, for optimum stabilization of 200 gr + bullets, you'll need a 1/7-8 twist barrel. That may not work well for lighter weight supersonic 308 loads.

Neither the 300 BLK or 308 will win any accuracy awards w/subs. 300 BLK makes for a better dedicated subsonic platform, but if you've got a 308, give it a whirl. Either is a lot of fun, just don't expect sub MOA accuracy.

@orkan wrote a good piece on a 300 BLK bolt gun project he built, exploring what accuracy was possible with subs as well as interesting thoughts on why it made for a good training rifle. I couldn't find the full write up, but here's a shorter extract relating to load workup - https://forums.gunhive.com/topic/395/new-ts-customs-300blk
 
  • Like
Reactions: garandman
spife7980 said:
The blackout in a bolt gun is a novelty.
Click to expand...
I'll be honest, I go back and forth with myself on this point. On one hand, the .308 route is absolutely, positively capable of more performance. As mentioned, you have the option to run everything from subs to full power .308, so again, it is absolutely, positively more flexible. For me, though, the caveat is that you kind of reach a point of diminishing returns (re: .308 advantages over 300 BLK) as barrel length drops below 20".

So, IMO, there is still a somewhat niche application for 300 BLK in a bolt gun, and that's as a walking hunting rifle for game up to ~whitetail size out to ~250-ish yards. With a 16" barrel, weight and length are minimized (to legal limits), and you're not throwing big fireballs when you pull the trigger. Recoil is also lower (vs .308), but you still have enough ass to get the job done with off-the-shelf ammo.

Or, maybe I'm just trying to justify my little RAR in 300 BLK; it and it's Eastern bloc cousin (Howa mini in 7.62x39) might just be my favorite general use knock-around guns right now... if I'm likely to find myself in a truck or side-by-side out riding around some land looking for nothing specific, those are the two rifles that I am most likely to grab.
 
I debated this, and went with the 300 Blackout. I've shot some very good groups with 208s over H110 even as subs.

Sure, it's a novelty and the 308 could be more versatile. But I have other guns for longer distances, and this does just what I want it to do.
 
  • Like
Reactions: Aceteck
For y’all using subs for hunting (thinking deer), what load (factory or reload) are you using?
 
I like my CZ 527 American Suppressor-Ready in 300 BLK. It's built on a micro-mauser action with 16.5" 1:7 twist barrel and has been 1 MOA or better with both factory supers and subs. I haven't had a chance to work up any hand loads for it yet.
 
PBWalsh said:
For y’all using subs for hunting (thinking deer), what load (factory or reload) are you using?
Click to expand...

I shot a doe through the shoulder at 40 yards with a 208 AMax. It worked, but only because the bone fragmented. If I was going to use this bullet again, I'd take a headshot.

I've got some of the Hornady Sub-X to try one day.
 
  • Like
Reactions: PBWalsh
PBWalsh said:
For y’all using subs for hunting (thinking deer), what load (factory or reload) are you using?
Click to expand...
For headshots it doesnt matter, just dont miss that brain because its the only thing going.

For body shots- I wouldn't- but if you are you want something to expand so I would go with the higher priced lehigh and makers bullets that are all copper to machined to expand easy.

This is a 220 sierra pro hunter at 1040 fps, it went into the front base of the does neck and traveled all the way through the back strap and stopped right where the muscle pinches out on the hips. It basically just took the soft lead off the top, Im assuming where it skipped off the neck bone, and kept on trucking.
7101211
 
  • Like
Reactions: dinc3 and PBWalsh
You must log in or register to reply here.

Similar threads

A
Dedicated subsonic bolt gun
Replies
64
Views
2K
45-90
4
O
Longest 300 BLK Barrel While Still Subsonic
Replies
12
Views
769
JerkyFreak
JerkyFreak
M
Failure to fire with AAC Ammunition
Replies
35
Views
360
Cascade Hemi
C
E
Question (potentially ignorant) on barrel swaps between two Ruger American Predators (.308 / 6.5cm
Replies
7
Views
212
estre
E
mrcheesemoose
300 blk 180 grain bullet loads?
Replies
11
Views
1K
db2000
db2000
Top Bottom
Back