300Blackout 8" SBR questions

[ARCHIVED THREAD] - 300Blackout 8" SBR questions

Posted: 4/13/2014 11:12:15 AM EDT

OK, so I'm hooked on the 300BO. I'd like to get an 8.2" upper for a rig I could carry under a jacket.

Do they have to be run with suppressors?

Love hearing only the bolt go back and forth.

Posted: 4/13/2014 11:38:40 AM EDT

[#1]

You don't have to run them with a suppressor, although that was their intention. Keep in mine a suppressor will basically make it about the same length as a rifle (approx. 16"). I use a Noveske Pig on mine (no suppressor at the moment) and many others do as well. The Pig helps to run both subs and supers reliably, as it helps with the back pressure. Not sure why you would want to keep it under a jacket though.....

Posted: 4/13/2014 2:52:51 PM EDT

[#2]

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Not sure why you would want to keep it under a jacket though.....

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Cause OP is in Somalia.

Posted: 4/14/2014 7:16:12 AM EDT

[#3]

Supersonics should cycle easily without suppressor. Subsonics might or might not cycle without suppressor. But might as well shoot supersonics anyway if shooting unsupressed.

I have a 8.5" bbl 300 Blackout and the bolt won't go back far enough to pick up the next round when shooting subsonics unsupressed (it'll eject the spent shell but then close up on an empty chamber). But put the can on and it runs all day long on subsonics. I'd rather have it like that anyway because it's not overgassed with the can on.

Mine is quiet enough to draw comments on the range but I want it even quieter so I ordered a JP Silent Captured spring and gonna try that next. Supposed to get rid of the buffer and spring noise.

Posted: 4/14/2014 7:29:05 AM EDT

[#4]

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Quoted:
Supersonics should cycle easily without suppressor. Subsonics might or might not cycle without suppressor. But might as well shoot supersonics anyway if shooting unsupressed.

I have a 8.5" bbl 300 Blackout and the bolt won't go back far enough to pick up the next round when shooting subsonics unsupressed (it'll eject the spent shell but then close up on an empty chamber). But put the can on and it runs all day long on subsonics. I'd rather have it like that anyway because it's not overgassed with the can on.

Mine is quiet enough to draw comments on the range but I want it even quieter so I ordered a JP Silent Captured spring and gonna try that next. Supposed to get rid of the buffer and spring noise.

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Could you run a slightly lighter buffer to solve that feed issue?

Posted: 4/14/2014 1:31:50 PM EDT

[#5]

I built an 8".300BO pistol upper. Runs fine with supers and subs, suppressed or going loud. Subs are 10.8gr gr of 1680 under a 200gr SMK.

Posted: 4/14/2014 1:42:55 PM EDT

[#6]

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Quoted:

Could you run a slightly lighter buffer to solve that feed issue?

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Quoted:

Quoted:
Supersonics should cycle easily without suppressor. Subsonics might or might not cycle without suppressor. But might as well shoot supersonics anyway if shooting unsupressed.

I have a 8.5" bbl 300 Blackout and the bolt won't go back far enough to pick up the next round when shooting subsonics unsupressed (it'll eject the spent shell but then close up on an empty chamber). But put the can on and it runs all day long on subsonics. I'd rather have it like that anyway because it's not overgassed with the can on.

Mine is quiet enough to draw comments on the range but I want it even quieter so I ordered a JP Silent Captured spring and gonna try that next. Supposed to get rid of the buffer and spring noise.

Could you run a slightly lighter buffer to solve that feed issue?

yes he could. I run a Spikes T2 in mine. I know alot of people run the H2, but it is too heavy for some and an H is too light. The T2 is right in the middle.

Posted: 4/14/2014 1:45:44 PM EDT

[#7]

My Noveske 8.2" upper runs subs and supers with or without the Sdn6 attached. I use the AAC fh/brake hybrid thing.

Eta: There's really no reason to shoot it without the can though, unless you're just waiting on a form 4.

Posted: 4/14/2014 1:55:40 PM EDT

[#8]

I couldn't get my 8.5" to cycle with a spikes T2 and subsonics, installed a T1 and it runs like a top. 300blk can take a bit of tuning. I would also recommend getting an adjustable gas block.

Posted: 4/14/2014 1:56:54 PM EDT

[#9]

Quoted:
OK, so I'm hooked on the 300BO. I'd like to get an 8.2" upper for a rig I could carry under a jacket.

Do they have to be run with suppressors?

Love hearing only the bolt go back and forth.

View Quote

It is louder than that. Made my ears ring a bit when fired under my patio. (8.5" Noveske w/ HVT) 220gr HPBT Sierra with Accurate 1680 sub loads.

Posted: 4/14/2014 6:30:19 PM EDT

[#10]

Using Rem 220 subs in my 8.5" with an AAC 762SDN6, it sounds like a .22.
Which, under a covered area, will make my ears ring too if I forget to put in plugs.

Not "Hollyweird quiet" by a long shot. (pun intended

)

Posted: 4/14/2014 9:05:21 PM EDT

[#11]

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Quoted:
I built an 8".300BO pistol upper. Runs fine with supers and subs, suppressed or going loud. Subs are 10.8gr gr of 1680 under a 200gr SMK.

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trying to chop my 10.5" noveske down to 8". Happen to know your gas port size? (No, noveske won't give out that info, already tried that).

Posted: 4/15/2014 6:01:24 AM EDT

[#12]

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trying to chop my 10.5" noveske down to 8". Happen to know your gas port size? (No, noveske won't give out that info, already tried that).

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Quoted:

I built an 8".300BO pistol upper. Runs fine with supers and subs, suppressed or going loud. Subs are 10.8gr gr of 1680 under a 200gr SMK.

trying to chop my 10.5" noveske down to 8". Happen to know your gas port size? (No, noveske won't give out that info, already tried that).

Lot of people use my data for reference for port sizing.

Note, all my data was obtained using an H2 buffer and standard power spring.

http://micromoa.com/?page_id=496

Also, note that I have found considerable variance in required port sizes from different blank sources...some rifling needs larger/smaller ports than others and some of this is due to the bore diameter....so YMMV!!

Posted: 4/15/2014 7:33:19 AM EDT

[#13]

What is the deal with pistol length gas systems? Why are they necessary?

Posted: 4/15/2014 8:05:24 AM EDT

[#14]

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What is the deal with pistol length gas systems? Why are they necessary?

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It needs more dwell time than 5.56...Pistol gas is required for anything shorter than 16" with 300BLK. I know some people may have gotten 14.5 to work with a carbine gas but for the most part you will need to go pistol gas.

I personally like pistol gas for all 300BLK configurations even for a 16"....if you cut down a 16" later, you don't have to re-locate the gas port and more room to go up in gas if needed. With 300BLK and carbine gas you are already close to max port size.