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308kiwi

Subsonic suppressed 308AR

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Have had this project on the go for a while, dedicated subsonic, suppressed, 308 upper, not even sure it's going to work yet but you never know until you try :-)

Finally after 6 weeks and dealing with translating Swedish to English and back to Swedish paperwork, my new suppressor turned up today, Over barrel Aimsport Triton 42S, made in Sweden. I'm particularly intrigued with the concept of this design, no baffles, instead it uses 3 large expansion chambers (I guess you could say it does have baffles, just not in the sense we are familiar with in suppressor design).

Barrel is 14", 1:10 twist, just need to cut the chamber, set head space and assemble it into the upper.

Mate of mine swaged me some 200gr projectiles to try, IMR Trail Boss powder, has proven itself well in the past with subsonic bolt rifle loads.

Will post up some more when I get it all together and see what happens:thumbup:

200gr1.jpg

200gr2.jpg

200gr3.jpg

200gr.jpg

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I noticed that you were "creating a topic" in this section, and I've been waiting to see what is was...    :laffs:

It was worth waiting on...   :thumbup:

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1 hour ago, 98Z5V said:

I noticed that you were "creating a topic" in this section, and I've been waiting to see what is was...    :laffs:

:laffs:

Trying to decide on where to go with the gas system has been a mission, pretty much came down in the end to replicating the AR15 300 BLK system that by all accounts gives the most reliable cycling with subsonic AR15 300 BLK loads, from what I found a 14" barrel with a pistol length gas tube seems to give adequate dwell time for 190-200ish gr projectiles being driven by sufficient gas pressure to keep them sub sonic but still cycle the rifle, I figure I'm doing nothing different except I have to drive a heavier BCG and recoil system, so this is where the specific suppressor comes into play, the design of the chambers is such that the gases are 'trapped' in the suppressor longer than a std baffle type design, I'm relying on this to boost the BCG via these gases escaping back down the barrel and giving the BCG a helping hand, 'delayed semi blow back' if you will, after all, this very phenomenon is what gives the accelerated BCG velocity in suppressed AR15's and 308AR's.

And if that all fails then I'll machine up a lightweight buffer and start playing with AR15 carbine springs to build a recoil system that replicates 300 BLK AR15 but behind a 308 BCG.

Now the suppressor has turned up I'm all motivated again to get this thing running, stay tuned:thumbup:

 

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5 hours ago, ARTrooper said:

wonder how it will compare to a 300 blk ballistics. would be pretty cool for deer hunting I think.

It should pretty much be the same I would have thought, given projectile at a given speed and spin should perform equally. I'm sure I'll be advised by some at some stage as to why I should have just built a 300 BLK upper......yep, fair comment but I want a quiet 308, I already have everything I need to make subsonic 308 ammo, have been loading it for years for bolt guns.

We have a big problem with feral goats over here and you have to 'quietly' shoot them cause as soon as they think they are in danger they are gone, I think this will be just the ticket for shooting these pests.

Edited by 308kiwi

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Just a thought from gleening info at the 300 BLK forum, not from personal experience.  I have never used Trailboss.

The impression I have is that Trailboss as a sub powder is great in bolt guns but will not cycle a gas gun due to lack of gas production.  This is in an AR15 Blackout with its smaller/shorter/lighter BCG than a 308 AR has.  You need a powder that creates enough gas to cycle the action yet keep the bullet subsonic.  There are quite a few that work in Blackouts,  in a 308 AR its a good question if there is one.

From personal experience with my suppressed 8" barrelled 300 BLK, the shooter barely hears the shot, you hear the action slamming back and forth next to your ear.  A suppressed AR will always be louder than a bolt action because of that, unless you shut off the gas so it won't cycle at all, but then why use an AR?

It might be worth your while to join the 300BLK forum and ask your questions over there.  There are guys there that have been shooting subs almost forever from ARs and they may be able to point you in the right direction and save some trial and error headaches

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11 hours ago, ARTrooper said:

wonder how it will compare to a 300 blk ballistics. would be pretty cool for deer hunting I think.

It should be the same ballistics as a 300 BLK.  A 200+ grain bullet going 1000fps or less is going to have the same trajectory whether its fired from a 308 or a 300 BLK.  Bullet weight is bullet weight, and muzzle velocity is muzzle velocity.  If its leaving the barrel at the same speed from both of the rifles firing it, the rifle shouldn't matter.  Its a rainbow compared to a 308 supersonic bullet.  My Blackout sub gun with 220 grain bullets sighted dead nuts at 50 yards puts bullets 5 inches low at 100 yards.  For hunting purposes I think of it as bow hunting with a rifle.  Inside 50 yards it will hit anything where I aim.  The one down side so far is that of the 3 deer I have taken with it none have left a blood trail.  I wasn't tracking any of them, I was looking for a dead deer.  All of them were just as dead as with supersonic bullets but just a challenge to find.  From now on I'll be taking neck shots and dropping them where they stand.   The Maker 200 grain Rex bullet recovered from my first deer taken with a sub.  Frontal shot into the chest and recovered from its stomach.

IMG_4202.thumb.JPG.41c2793b59d11906645293fe52473a00.JPG

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^^^  That opened up NICELY!  That's at least an inch across those petals?...

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Yup, about an inch.  The two deer this year were both broadside shots, complete pass throughs with nice triangular exit wounds and NO bloodtrails.  A ton of blood inside the chest cavity but none made it out.  A subsonic bullet does not have the hydrostatic shock of a super.  They act more like an arrow's broadhead, especially this type of bullet.  Slices and tears what it comes in contact with but not much collateral damage to surrounding tissue.  No organs turned to mush. 

If you are close enough you can hear the bullet hit the deer.  It sounds like a person wearing heavy leather gloves clapping their hands once.  Thud!

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19 hours ago, dpete said:

It should be the same ballistics as a 300 BLK.

yeah from my little research I did after this thread came up, it looks like it has the same ballistics because uses the same size bullets at the same velocity. I wasn't sure if with a .308 someone would be loading even heavier bullets, such as the 250gr to 300gr range, to increase energy on target... but maybe that would make it to long to cycle in an 308ar.

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giggidy! this is neat with picks!  ive only shot a hand full of sub .308 suppressed. its not as quiet as the .300  even in the bolt gun but sure is fun!  good work kiwi! 

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Another question is whether the barrel has a fast enough twist rate to stabilize a heavy bullet going subsonic slow.  A lot of .308 barrels are 1:10 and shoot 150 to 178 grain bullets at 2000+fps just fine.  Load a 220+ grain bullet in there and only have it going 1000fps how long is it going to be stable before it wants to keyhole into the target?

Blackout barrels are 1:7 or 1:8 twist so they can stabilize those monsterous bullets at crawling speeds.

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18 minutes ago, dpete said:

Another question is whether the barrel has a fast enough twist rate to stabilize a heavy bullet going subsonic slow.  A lot of .308 barrels are 1:10 and shoot 150 to 178 grain bullets at 2000+fps just fine.  Load a 220+ grain bullet in there and only have it going 1000fps how long is it going to be stable before it wants to keyhole into the target?

Blackout barrels are 1:7 or 1:8 twist so they can stabilize those monsterous bullets at crawling speeds.

Yeah, I've considered that, every load is going to be printed before the suppressor gets screwed on, do not need to be tumbling bullets sideways through an expensive suppressor.

Am going to start with 200gr, but I've got a decent selection of .30 bullets ranging from 135gr to 220gr to try. My barrel is 1:10.

On 2/6/2019 at 2:28 PM, dpete said:

Just a thought from gleaning info at the 300 BLK forum, not from personal experience.  I have never used Trailboss.

The impression I have is that Trailboss as a sub powder is great in bolt guns but will not cycle a gas gun due to lack of gas production.  This is in an AR15 Blackout with its smaller/shorter/lighter BCG than a 308 AR has.  You need a powder that creates enough gas to cycle the action yet keep the bullet subsonic.  There are quite a few that work in Blackouts,  in a 308 AR its a good question if there is one.

 

Good points dpete, I'm leaning along the line of thought that it is pressure that I need rather than a quantity/volume of gas, and like has been discussed, a given weight projectile needs x amount of pressure to drive it at x velocity, so from that, I already know from experience that Trail boss can easily drive 175 to 200gr projectile to 1050 fps, (in a bolt rifle), so must be generating the same amount of pressure as any sub sonic load in 300 BLK, or any other calibre for that matter, that is achieving the same results.

Hence my decision to go with a pistol length gas system and a 14" barrel, giving as much exposure of that pressure to the gas system for as long as possible, like I said, that combination of gas port location vs barrel length seems to work well with 300 BLK, the only reason Trail boss isn't used in 300 BLK is that the bulk density of the powder is so high that you simply cannot get enough of it in a 300 BLK case.

If I get some spare time this month it will all be academic cause I'll know if it cycles or not and rest assured I'll be posting it here.😃

FWIW, these guys are doing it using 220gr projectiles and loading 14.5gr of IMR4759 powder which is pretty close to H110 apparently, I just do not want to be dealing with the hassles of loading such small amounts of powder and the inherent problems that come with that.

https://www.youtube.com/watch?v=rYGrAsCRWTs

 

 

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3 hours ago, ARTrooper said:

should have just gone with a .375 raptor. 😛

:laffs:I have been seriously looking at the 375 Raptor as well.

If this project doesn't work out I will have a spare BCG, Upper, barrel extension etc in need of a new barrel.............Hmmmmmmmmmm

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5 hours ago, dpete said:

358 Yeti.......................just sayin'

different platform. the 375 raptor would be 20 rounds in a 308ar with more case capacity. also a .375 caliber bullet up to 350 grains. so all subsonic will be traveling around the same speed no matter the caliber, so the only thing that will really increase energy on target is the weight of the bullet, and wound channel will be increased with size of bullet. 

with the 375 raptor, you only need to replace the barrel. you can use .308, .338 federal, and .358 win cases to reload. it is basically like the .300 blk, but a little larger for a 308ar platform.

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8 hours ago, ARTrooper said:

with the 375 raptor, you only need to replace the barrel. you can use .308, .338 federal, and .358 win cases to reload. it is basically like the .300 blk, but a little larger for a 308ar platform.

I turn my .308 match brass into .260 Remington.  I turn the .308 general brass into .338 Fed.  Maybe .358 Win in the future.  Why do I want another caliber eating up my stock of .308 brass?!...  :laffs:

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2 hours ago, 98Z5V said:

Why do I want another caliber eating up my stock of .308 brass?!...  :laffs:

because you can only build so many grendels. lol.

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Fucking Grendels.  I'm telling you, they're trashing the stock right now, overpopulating.  It's just about assinine.  If they weren't so damn good at distance, I wouldn't have this problem... 

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Go register the name “98’s Grendels” Get an FFL and start Selling. 💰If you can’t escape them, at least make some money off them.

Edited by Sisco

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9 hours ago, 98Z5V said:

Fucking Grendels.  I'm telling you, they're trashing the stock right now, overpopulating.  It's just about assinine.  If they weren't so damn good at distance, I wouldn't have this problem... 

the first step is admitting you have a problem. the next step is getting help. I am here to help you brother. I will take the temptation off your hands for you. 😉 

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3 hours ago, ARTrooper said:

the first step is admitting you have a problem. the next step is getting help. I am here to help you brother. I will take the temptation off your hands for you. 😉 

You have no idea. Wait to you get his place in a few weeks. It’s pure comedy! “I forgot about that guy!” Is said more than once. And when he opens and unloads the hang box? You better get some tissues or towels ready to clean yourself with!

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