Subsonic .308 for suppressed rifles

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11 years 5 months ago #24497 by txlongshotb4
Subsonic .308 for suppressed rifles was created by txlongshotb4
After nothing short of a metric butt-ton of research, I have finally decided that I am comfortable enough to explore the waters of reloading my own subsonic .308 ammo. Tommorow morning I plan on being at the local range when the gates open, and I have several boxes of loads I've worked up for my rifle to try out. Ten of those rounds are subsonic-I hope. I've started these experimental rounds in Lapua brass with CCI large rifle primers, and 10 grains of IMR Trail Boss under Sierra 180 grain Match Kings.

I do not currently have a chronograph. I was hoping to have purchased one prior to tomorrow morning, but the stars have not yet alligned and as of now I do not have one-so I will not have any velocity reports...This is an error I do intend to correct in the very near future. When I do so, I will post some velocities. For now, I plan to shoot these ten rounds unsuppressed. If I can get A-all ten rounds to actually exit the muzzle ((I'm pretty sure they will.) and B- no keyholes at 100 yards, I will call it a small victory. I will do my best to group the load and report on the accuracy, but subsonic ammo can be quite tricky when it comes to getting it to behave...even factory stuff. If I have satisfactory results tomorrow I will load up ten more and shoot them suppressed to check for sonic pop-since I have no chronograph yet.

I will be updating this thread as this project progesses forward, in the interest of those who would like to load their own subsonic .308 ammo. Once I get a chronograph and finally decide on a good load I will post velocities and dope in minutes of angle and mil holds for the load's ballistics from 25 meters to however far they wind up being able to keep it together...probably 200 to 250 yards or so.

Intel will be forthcoming guys-watch this thread.
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11 years 5 months ago #24506 by 13fcolt
Replied by 13fcolt on topic Subsonic .308 for suppressed rifles
You still don't have a chrony?!?!
Anyway. I'm following this.

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11 years 5 months ago #24511 by Lizardette
Replied by Lizardette on topic Subsonic .308 for suppressed rifles
Excellent!

I'd heard of using Trail Boss for sub-sonic .308 loads, but the guy I talked to was using 168's.

Definitely want to hear your results though.

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11 years 5 months ago #24533 by OleCowboy
Replied by OleCowboy on topic Subsonic .308 for suppressed rifles
I personally am not sure of the need for subsonic rds, but I follow with great interest, maybe something will enlighten me...

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11 years 5 months ago #24592 by txlongshotb4
Replied by txlongshotb4 on topic Subsonic .308 for suppressed rifles
OK...I have taken my subsonics to the range. I also bought myself a new chronograph today, as working up subsonic loads without a chronograph is a pretty silly endeavor.

The good news, all of the rounds I fired made it out of the muzzle, and I didn't plug up my tube and facilitate the need to pound a cleaning rod down my match grade barrel.

Muzzle velocities were both a tad high and the string varied quite a bit. I fired five rounds, at an average velocity of 1040fps. My low was 1019, and my high was 1057 The Trail Boss is a very light powder, and so 10 grains fills the cases up to just under halfway. If I had to guess, I think the wide variance in velocity has to do with the ammount of dead space I have in the cases. Lapua sells factory loaded subsonic ammo in a 200 grain bullet, but it is seated deep so that the overall cart. length is just over 2.60. I believe that they seat their bullets deeper to minimalize the dead air inside the cases. I have an email into their tech support about this, and it's an area I intend to explore.

The bad news is, I could not get the rounds to stabilize at all. I fired five rounds into paper at 100 yards, and all five rounds had tumbled in flight and "keyholed" my target. Interestingly enough, they all managed to keyhole into a 3 inch group...but tumbleing bullets and suppressors do not get along at all, so it's back to the drawing board for this project.

I think for the next chapter I am going to give the 175s a shot, and bump the charge weight down to 9 grains...but I really want to push heavier bullets for these loads. I have seen a lot of talk on other forums about guys getting good results using 200 grain round nose bullets like what would be found in 30-30 loads. I plan to explore this route as well.

I'll keep you all posted!
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11 years 5 months ago #24595 by txlongshotb4
Replied by txlongshotb4 on topic Subsonic .308 for suppressed rifles
I personally am not sure of the need for subsonic rds, but I follow with great interest, maybe something will enlighten me...

Some guys use them for pest and varmit control with suppressed rifles in places where loud noises upset cranky neighbors, particularly at night when coyotes like to visit the chickens and the kids are sleeping. I use them just becuase it makes my suppressed .308 sound like a nail gun, and I get a kick out of it-but Lapua subsonics are about 54 bucks per 20 rounds, so I want to make my own and pocket the loot. In researching this, I've found a lot of posts on other forums from guys who are passing along second or even third hand knowledge, in some cases they haven't actually tried it. I want to put some data out there that I can back up with personal experience via trial and error so guys who want such data will have a good starting point.
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11 years 5 months ago #24596 by SOC
Replied by SOC on topic Subsonic .308 for suppressed rifles
If I were to go the 30cal subsonic rout I'd probably build a 7.5" 300 Blackout AR using a Noveske barrel.

240gn subs or 110 V-max at 2400fps.

FYI the best powder for 300 Blackout is H110, also good for .357, .44 mag and .454 Casual.

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11 years 5 months ago #24600 by Lizardette
Replied by Lizardette on topic Subsonic .308 for suppressed rifles
I feel obliged to give some information on bullet stabilization here.

I don't remember off the top of my head what the twist rate of your barrel on this rifle is. If it's the common 1:11 twist that Armalite uses, you might not even be able to stabilize 180 grain match kings at supersonic velocities. The twist rate needed to stabilize a bullet of a given length* is faster when its velocity is lower. Basically, at subsonic velocities, you might only be able to stabilize shorter (and therefore usually lighter**) bullets with the twist rate in your barrel.

I've heard, but haven't been able to confirm, that a 1:10 twist barrel will stabilize a 168 grain match king bullet at subsonic velocities. I'll see if I can talk to the man again and get some more information about it.

Oh, also important to know: Did the loads you used actually cycle your rifle?

* According to AnarchAngel ( anarchangel.blogspot.ca/2007/01/stabilization-mythology.html ), the relevent measurement of the bullet in relation to stabilization is length, not weight.

** At one time, I know Midway USA sold 5.56 bullets the same length as the standard 55 grain FMJBT that weighed 75 grains. It had a bismuth core instead of lead.

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11 years 5 months ago #24641 by OleCowboy
Replied by OleCowboy on topic Subsonic .308 for suppressed rifles

txlongshotb4 wrote: I personally am not sure of the need for subsonic rds, but I follow with great interest, maybe something will enlighten me...

Some guys use them for pest and varmit control with suppressed rifles in places where loud noises upset cranky neighbors, particularly at night when coyotes like to visit the chickens and the kids are sleeping. I use them just becuase it makes my suppressed .308 sound like a nail gun, and I get a kick out of it-but Lapua subsonics are about 54 bucks per 20 rounds, so I want to make my own and pocket the loot. In researching this, I've found a lot of posts on other forums from guys who are passing along second or even third hand knowledge, in some cases they haven't actually tried it. I want to put some data out there that I can back up with personal experience via trial and error so guys who want such data will have a good starting point.

I have a friend that has a Ruger 10/22 and he uses subsonic and he has a can on it also. He lives in a gated neighborhood and has a real problem with squirrels and snakes (Water Mocs) as his home fronts the lake and its a shallow grungy thing which sakes up bad every spring.

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11 years 5 months ago #25493 by txlongshotb4
Replied by txlongshotb4 on topic Subsonic .308 for suppressed rifles
OK...I had taken a little bit of a break from this project to handle some other things, but my nose is now back to the grindstone so to speak. I have loaded up another batch. This time, I used 8.5 grains of trailboss under Hornaday match 168 grain BTOTM. I know my best bet probably lies with 175 grain bullets, ( my barrel is a 1 in 11 3-groove twist, by the way.) but I only have about 23 Berger VLD match 175s left and they are the best thing I've got for my supersonic loads-I don't want to burn them up on R & D for novelty rounds. That chapter of the story will have to wait until resupply becomes available again.

The interesting thing is, my rifle has been stabilizing the Lapua 200 grain subsonic stuff just fine. I've shot just over 100 rounds of the stuff through it, and I've never had any issue...very strange. I suppose that means I need to try to duplicate the 200 grain bullet-but there again-resupply.

Anyhow, I plan on sneaking out to the range for an hour or two this weekend to chrono these loads and see if they stabilize-I will update afterwards.

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