18.6-20in 300BLK AR Barrel?

I have a Odin blackout barrel 18.6” in my sporter. It did not cycle reliably until I opened the gas port up as well as ran s lightweight carrier. It cycles all ammo now, but took a lot of trial and error.

Just curious, can you give a build list of BCG, buffer and buffer spring. Also, is it carbine or pistol gas system.
Strange that it came with too small of a gas port.
 
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Odin barrel is carbine gas
I'm currently running a TiN lightweight carrier from Brownells, a giessele H1 buffer, and a lightened buffer spring from tier one armory.
I switched the supplied gas block out to a superlative adjustable to dial the gas down for hotter rounds.
I'm also running a thread protector on the barrel from ATRS as the brake I got from vg6 was threaded crooked.
Gas port is drilled to 0.130" , original hole was around 0.100"
 
Anyone using one found the report of subsonics in a long barrel quieter than a normal round? What would you compare it to?
 
Anyone using one found the report of subsonics in a long barrel quieter than a normal round? What would you compare it to?

Still need hearing protection but barely. Kinda like shooting a non restricted 9mm carbine if you've ever shot one of them.


@CR5 Both are handloads. I do H110 for both, 150 grain supersonic and 230 grain cast.

Try using A1680 for the 230's, will work a lot better and should be able to cycle them subsonic with it.
I only use H110 for my 140gr or less supersonic loads. Lil'Gun for 140-170ish weight supersonic, and A1680 for 150gr supersonic and 200+subsonic.
Those are my go-to powders for 300BLK but I've loaded up some using IMR4227 but haven't tested them yet.

Maybe you did but I would have definitely tried some different powders before opening the gas port.
One thing that guys sometimes don't realize is that just because it's published data doesn't mean that it will cycle a semi auto rifle. I know this doesn't really make a lot of sense since the round was developed to be used in an AR but it is our reality.


Just some data for anyone interested
http://www.xcr.ca/CustomReloadingData.numbers.pdf
 
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I don't know if you checked them but Alberta rifle tactical supply quoted me for 1 but they told me they terminal ballistics of it I didn't care I just wanted to 18 inch barrel that's rifle length gas system lol, I didn't buy it yet tho
 
I don't know if you checked them but Alberta rifle tactical supply quoted me for 1 but they told me they terminal ballistics of it I didn't care I just wanted to 18 inch barrel that's rifle length gas system lol, I didn't buy it yet tho

You don't want a rifle length gas system for 300BLK, you will have a hard time getting it to cycle.
And you don't want 18 inch, you want 18.5 inch or it will be restricted.
 
https://www.thetruthaboutguns.com/2014/11/foghorn/ask-foghorn-questions-300-aac-blackout-rifle/

For cr5 asking about the barrel length.

And your own chart is showing the diminishing returns in performance from each inch of extra barrel length.

I never said it won't gain velocity but it's diminishing returns for extra weight... it's just over 400fps gain from a 9inch to a 24 inch... almost 800fps difference between the same barrel lengths on 556 keeping in mind 556 requires the muzzle velocity to maximize its terminal capabilities. The 300bo does not making the relatively minor velocity gains a bit irrelevant.

The inception of the 300 bo was to be effective as a sbr suppressed or not. Factory loaded 300bo is set up to burn fast and get the performance out of a shorter barrel hence the pistol length and carbine length gas systems. And the lack of fireballs compared to similar short 556 guns.
 
https://www.thetruthaboutguns.com/2014/11/foghorn/ask-foghorn-questions-300-aac-blackout-rifle/

For cr5 asking about the barrel length.

And your own chart is showing the diminishing returns in performance from each inch of extra barrel length.

I never said it won't gain velocity but it's diminishing returns for extra weight... it's just over 400fps gain from a 9inch to a 24 inch... almost 800fps difference between the same barrel lengths on 556 keeping in mind 556 requires the muzzle velocity to maximize its terminal capabilities. The 300bo does not making the relatively minor velocity gains a bit irrelevant.

The inception of the 300 bo was to be effective as a sbr suppressed or not. Factory loaded 300bo is set up to burn fast and get the performance out of a shorter barrel hence the pistol length and carbine length gas systems. And the lack of fireballs compared to similar short 556 guns.

Not sure what your point is, if you don't like the 300BLK then move along, this thread is for guys wanting info on the cartridge in an 18.5+ inch barrel, if you just want to come in and crap on it and say it's pointless I doubt anyone here is going to care what you say.
The 300RUM is only about 300fps faster than a 300 Win mag but people don't dispute that it's an improvement in trajectory and terminal energy. Any increase in velocity gives a flatter trajectory and is an increase in terminal performance and thus not irrelevant.
Regardless of any of that the point is that some people like the 300BLK and want to know if it will work well in a non restricted rifle with an 18.5 inch barrel. My point is that it works very well with a long barrel and even if it's only a couple hundred fps faster the point is that it is accurate and cycles reliably if set up correctly.
People continually say it's optimized for short barrels and suppressors which just isn't true, It was designed to function correctly in that configuration which is great if you ever get a chance to shoot one, I've shot short barrel suppressed full auto 300BLK with full capacity magazines and it's awesome but it works just as well or better in a longer barrel if you consider increased velocity better.

The only thing I've found a little difficult with the longer barrel is building a subsonic load that will cycle the action, it's hard to get it to stay subsonic and still cycle but I do have loads that do it even though it's kinda pointless since it's still loud enough to need hearing protection if you don't have a suppressor.
The most fun I've had with subsonic loading for the 300BLK is for my bolt action, a little trailboss under a 150gr FMJ is super quiet, cheap to build, and fairly accurate. Unfortunately it will not cycle a semi auto.
 
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Not sure what your point is, if you don't like the 300BLK then move along, this thread is for guys wanting info on the cartridge in an 18.5+ inch barrel, if you just want to come in and crap on it and say it's pointless I doubt anyone here is going to care what you say.
The 300RUM is only about 300fps faster than a 300 Win mag but people don't dispute that it's an improvement in trajectory and terminal energy. Any increase in velocity gives a flatter trajectory and is an increase in terminal performance and thus not irrelevant.
Regardless of any of that the point is that some people like the 300BLK and want to know if it will work well in a non restricted rifle with an 18.5 inch barrel. My point is that it works very well with a long barrel and even if it's only a couple hundred fps faster the point is that it is accurate and cycles reliably if set up correctly.
People continually say it's optimized for short barrels and suppressors which just isn't true, It was designed to function correctly in that configuration which is great if you ever get a chance to shoot one, I've shot short barrel suppressed full auto 300BLK with full capacity magazines and it's awesome but it works just as well or better in a longer barrel if you consider increased velocity better.

The only thing I've found a little difficult with the longer barrel is building a subsonic load that will cycle the action, it's hard to get it to stay subsonic and still cycle but I do have loads that do it even though it's kinda pointless since it's still loud enough to need hearing protection if you don't have a suppressor.
The most fun I've had with subsonic loading for the 300BLK is for my bolt action, a little trailboss under a 150gr FMJ is super quiet, cheap to build, and fairly accurate. Unfortunately it will not cycle a semi auto.

At which point did i crap on it?

I never said it doesnt work well out of longer barrels. I'm saying the cartridge is optimized for shorter barrels. And as you said the longer barrels does take away from some of the rounds versatility.

And it explains why there are very few 18.5+ options available commercially.
 
How much does having an adjustable gas block negate the advantage/inconvenient of the different gas systems?
 
At which point did i crap on it?

I never said it doesnt work well out of longer barrels. I'm saying the cartridge is optimized for shorter barrels. And as you said the longer barrels does take away from some of the rounds versatility.

And it explains why there are very few 18.5+ options available commercially.

There are very few 18.5+ options available because until very recently when we've had non restricted platforms that take AR barrels there has been no demand for them.


How much does having an adjustable gas block negate the advantage/inconvenient of the different gas systems?

An adjustable gas block allows you to reduce the amount of gas delivered to the operating system. Not going to help the situation of using a barrel with the wrong length to the gas port. If you used a rifle length gas system you might be able to get it to cycle with 110-150gr supersonic loads but nothing is for sure and it's an awfully expensive purchase to simply try it out and hope. If you're not a handloader and also not going to go with the proven gas system lengths then your chances of success are slim.
One of the guys on the site tried to get a 300BLK barrel (Odin if I recall correctly) to work in his WK-180C and it took a lot of messing around and drilling out the gas port just to get it to cycle 110gr loads. I'm not even sure if he actually got it to work 99% of the time. Not sure why he had so much trouble, it should have worked but I didn't get to look at it so can't really troubleshoot it. The WK gas system must not be ideal for the 300BLK pressure curve, I'm guessing it needs a little larger gas piston to work with 300BLK.
I had a barrel custom made with a carbine length gas system for my ACR and it worked great once I figured out the size the gas port needed to be.
 
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Depending on what gas system you want we have IBI 18.6 300 black out barrels in stock. I'm assuming you want a pistol length. If so shoot us an email. If you want something special just let us know because our new order of barrels will be here in four weeks and we can add to the order if you like. Right now we have IBI 18.6 1/8 twist 5r rifled pistol length barrels for ar-15 in stock for 399.00.

Cheers, RWA
I can likely change gas system lengths fairly easily as well if need be fellas.
 
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