Good evening all.

Im in the beginning stages of my 2nd overall build, 300 blackout.
I was at my LGS speaking with the gunsmith. I explained I'm in the market currently for a 9" or 9.5" barrel (pistol length) to ideally run with a can and subsonic ammo.
I began inquiring on the gas system.
He asked If I would run a can ALL the time. I replied that I'd obviously like the option to remove the can and run it without it if I felt like it.
He then goes to the back and brings me a pigtail gas tube.
He recommended installing that into my build because this way I can run subsonic ammo with the can on. I then could remove the can and run reg or supersonic ammo. He stated that if I installed a regular pistol length gas tube and attempted to run it without the can, It would not cycle the reg or supersonic ammo efficiently.
I'm asking on any feedback regarding these pigtail gastubes as honestly I knew nothing about them and from what I understand these 300 builds can provide some headaches regarding the rifle cycling.

Thanks

The 9" BCM 300 barrels are supposed to run subs or supers well. At worst you might have to change the buffer depending on specific round.

If you buy a good barrel you will almost never run into any cycling problems.

Just about every reputable barrel manufacture will have the proper port size to run supers suppressed or unsuppressed and subs suppressed without any problems or having to change anything. Some will not reliably cycle subsonics without a suppressor.

Pig tails only add problems and are not needed with a good barrel.

The 300BLK was made to cycle supers and subs suppressed without any modifications to the gas block, gas tubes or having to change buffers depending on what round you are shooting.

I have over 10 of them ranging from 8.0 inches to 16 inches. Some of the 16 inches run carbine gas tubes the rest all run pistol gas tubes and none of them have a pig tail or an adjustable gas block. I have shot hundreds of rounds through each. With some seeing thousands of rounds with no problems.

If your standard 300BLK doesn't cycle 100 percent with holding the bolt back on the last round in those 3 configurations of supers both suppressed/unsuppressed and subs suppressed. Then you have bought a barrel that is sub par or something is wrong with your rifle and a pig tail is not going to help.

Thanks for the feedback fellas.
I've been actually looking at BCM's 9" and Ballistic Advantage's 9.5".

Would you guys consider BA's barrels to be of that quality mentioned above?

I have not had any problems with my two DI blackout builds using a standard pistol gas tube. I run two different suppressors and shoot supers and subs without the cans all the time. If you want to control gas flow I would recommend an adjustable gas block not a pig tail tube. Pig tails are hype if you ask me.  Most of the people who have had headaches with Blackout either have one of the following problems

1. Have a misaligned gas block (probably the most common) or an improperly drilled gas port
2. Bought a carbine length gas barrel (some carbine gas work fine but why chance it go with a pistol gas)
3. Using really sh-tty ammo
4. (This one I did) Put unproven equipment together for the build.  I tried a Syrac Piston with a PDW stock. The SBR is a DI blackout now.

IMHO Stick with a good pistol length gas system, good barrel,  and DI (with the adjustable gas block as a option) and your blackout will rock. If you dont reload your blackout will get you into that too

His theory being you need the longer tube to run supers unsuppressed, but now you've got he same thing as a carbine length tube when you want to run subs suppressed.  It's easier to deal with over gassed supers than undergsssed subs.  Just put an adjustable gas block on a standard pistol tube.

BA makes great barrels all my builds have them

Thanks for all the feed back fellas.
Much appreciated.

In my shop the I will only sell barrels for 300BLK that have a pistol length gas system. I have had no reported problems, suppressed or unsurpassed, subs or supers.

Yeah, I would try with the standard pistol length set up and wait to see if you have any issues.  This is the beautiful thing about 300 BLK- run it subsonic, supersonic, subsonic suppressed, or supersonic suppressed, short or long barrel, it usually works fine.

I have built several sbr's and pistols with 8" and 9" barrels.

I have looked at the pigtail and understand it is supposed to delay the unlocking of the bolt so it unlocks while pressures are lower.

However, I have not needed this in any of my 300 builds.

Most problems are gas flow variances between suppers and subs.

Most often factory loaded subs that are loaded to run sub out of a 16" barrel.

When these are run in an 8" barrel their velocities are much lower and sometimes there is not enough gas to cycle the action unless a suppressor is used.

Good handloaded subs solve that problem.

I don't want to derail this thread, but I am building my first 300Blk and have a similiar question:

Using a 10.3" Daniel Defense S2W barrel, with pistol-length gas system. Do I need a standard gas-block? My plan is to shoot subsonic with a Dead Air Sandman-S 99% of the time.

From my reading, and no experience shooting 300Blk- if it runs subs, with a can reliably, would supersonic ammo not function fine with/without a can, using a standard non-adjustable gas block?

My 300BO build is Aero upper and lower. BA 9.5" barrel 1/7 twist. Pistol gas. Functions all 4 ways. I use a standard carbine buffer. Micro gas block, non-adjustable. Zero issues.

AAC SDN 6 can.

Also Ballistic Advantage your barrel kicks ass as far as accuracy!!!

You should be fine running supers with/without a can. As mentioned above, subs unsuppressed may be too weak to cycle. No need for an adjustable GB on .300 BLK as they don't have the overgassed issues like 5.56.

Thanks for the replies guys.

I have no desires to shoot subs without a can. Between 7.62x39, x51 & 5.56 I have enough barrel lengths and combinations that this 300Blk build is just for quiet time only, but would hate to find out the hard way that it had issues with unsuppressed supersonic ammo.

You should be fine with a standard gas block. Adjustable blocks are really an insurance policy just in case but it's not necessary. Adjustable blocks are nice if you want to turn off the gas

If there is not enough gas to run subs, an adjustable block will not make more gas.

Makes sense. Planned to run standard carbine buffer. Will that be ok with a can or should I go up to H or H2?

That's a good point and something I considered doing a while back. An "off" position could be a ton of fun to kill the action noise and make an incredibly quiet single shot.

Well my Geissele MK8 rail comes with one of their Low-Profile gas blocks, so I will use that, since it was free.

For a BCG does 300Blk benefit from any of the fancier ones? I have a standard Rainier Arms BCG that has been kickin around for awhile.

If you intend to run a can on it, then a fancy carrier like the NP3 ones may make cleanup easier.    I have also had really good results with melonited carriers running better in my suppressed 5.56's compared to parkerized carriers.

I still run regular parkerized BCM or LMT bolts, though.

As mentioned above I prefer something like chrome bolts/carriers on all my AR builds as they are easier to clean.

My budget build $100 KAK 8.5" pistol gas barrel runs both subs and supers both suppressed and non-suppressed just fine.

Awesome info. Thanks guys.

Right now I am tapped for funds with other projects and Christmas, so trying to just get a 300Blk upper built and running, then down the road can swap out parts for "upgraded" versions.

Got a free Geissle gas-block with my Mk8 rail, but I am going to paint it, since it's an all-black build, with a bright silver gas block