300blk/dissipator

Chazp89 · Oct 19, 2017

I have a couple questions on the ar platform...
With 300 blackout, what is the advantage of running a pistol gas system with a 16” barrel? My assumption is that it helps the rifle cycle subsonic ammunition. Is there a problem with over gassing with supersonic when using that setup?

Also, I’m planning a mock dissipator build using either 300 blk or 9mm. Are there any particular barrels in either caliber that anyone can think of that would have the proper contour for a standard .750 fsb in the rifle location?

Hell while I’m at it, has anyone played with 7.62x40wt?

DaemonAssassin · Oct 20, 2017

No issues with supers or subs with a pistol length gas system.

You won't find a dissipator barrel for 300BLK, because the most you would find is a carbine length or pistol length gas system.

Chazp89 · Oct 20, 2017

Thanks but I think my question got a bit lost in translation and I should have explained more with the mock dissipator.

I have a 300 blk with 16” and carbine has system, it doesn’t cycle subsonic, I assume if I switch to a barrel with a pistol system it would run subsonic ammo, but would I have any issues with supersonic?

As for the mock dissipator... if I use 300 blk, I’ll run a pistol or carbine system with a low profile gas block that hides under the hand guards then use a standard fsb in the rifle location as a dummy. I’m just looking to see if anyone knows of a particular barrel that would have the right diameter around the rifle mounting location to put a fsb. Either in 9mm or 300blk

Chazp89 · Oct 20, 2017

Sorry I was a bit to quick reading your post, I missed that you mentioned supersonic

RJRjr · Oct 20, 2017

Palmetto has a 300 blk dissipator upper I think

clandestine · Oct 20, 2017

Carbine Gas can be made to run subs. It just takes a little bit of work.

teratos · Oct 20, 2017

A dissipator build may be nice for .300 BLK supers. If you are going to shoot subs, I wouldn't do it, or I would have 2 uppers for the gun.

Chazp89 · Oct 20, 2017

clandestine said:
Carbine Gas can be made to run subs. It just takes a little bit of work.

What can I do to make a carbine shoot subs? Enlarge the gas port and/or reduce buffer weight?

Melnic · Oct 20, 2017

OP, Seems like some of your post is getting misinterpreted. So what you want is Pistol gas system but you want the front sight out near the muzzle so you get the advantages of a long sight radius but still maintain a pistol gas system? To accomplish that, you would have a low profile gas block for the pistol length under the hand guard, but add an FSB w/o using the gas in it for the front sight?

I have a 300blk on an SBR but was thinking about the same thing at one point so I'm very interested. I like shooting offhand with irons.
I was however hoping for it to be floating and not have handguard touch FSB

My googlefu came up with this. Scroll down for a pic (its a carbine length , but illustrates what you are asking about)
http://www.300blktalk.com/forum/viewtopic.php?t=90205&start=10

outrider58 · Oct 20, 2017

Melnic said:
OP, Seems like some of your post is getting misinterpreted. So what you want is Pistol gas system but you want the front sight out near the muzzle so you get the advantages of a long sight radius but still maintain a pistol gas system? To accomplish that, you would have a low profile gas block for the pistol length under the hand guard, but add an FSB w/o using the gas in it for the front sight?

I have a 300blk on an SBR but was thinking about the same thing at one point so I'm very interested. I like shooting offhand with irons.

My googlefu came up with this. Scroll down for a pic (its a carbine length , but illustrates what you are asking about)
http://www.300blktalk.com/forum/viewtopic.php?t=90205&start=10

What the OP is looking for is a 300AAC barrel that will maintain proper diameter out to the muzzle so a faux FSB can be either pinned(preferably) or clamped on. That may be hard to find. He may have to resort to a front sight mounted to the end of a long hand guard. Not the best solution, but a reasonable($) alternative.

Chazp89 · Oct 20, 2017

Melnic said:
OP, Seems like some of your post is getting misinterpreted. So what you want is Pistol gas system but you want the front sight out near the muzzle so you get the advantages of a long sight radius but still maintain a pistol gas system? To accomplish that, you would have a low profile gas block for the pistol length under the hand guard, but add an FSB w/o using the gas in it for the front sight?

I have a 300blk on an SBR but was thinking about the same thing at one point so I'm very interested. I like shooting offhand with irons.
I was however hoping for it to be floating and not have handguard touch FSB

My googlefu came up with this. Scroll down for a pic (its a carbine length , but illustrates what you are asking about)
http://www.300blktalk.com/forum/viewtopic.php?t=90205&start=10

You pretty much nailed what I have in my head. I’m not dead set on pistol length gas, just trying to find some feedback on it since I’ve never run it.

Chazp89 · Oct 20, 2017

outrider58 said:
What the OP is looking for is a 300AAC barrel that will maintain proper diameter out to the muzzle so a faux FSB can be either pinned(preferably) or clamped on. That may be hard to find. He may have to resort to a front sight mounted to the end of a long hand guard. Not the best solution, but a reasonable($) alternative.

Yes most definitely, I’m starting to learn that it may be a better idea to keep one question per thread haha

Chazp89 · Oct 20, 2017

Just to clear it up, I have a couple questions in this thread originally

-pistol gas systems with 300blk, why? What are the advantages over carbine?

-mock dissipator, does anyone know of any 300blk barrels in either gas system either 16” or 14.5” with a profile that has .750 diameter around where a rifle length gas block would be.
Also same question but with 9mm

clandestine · Oct 20, 2017

Chazp89 said:
What can I do to make a carbine shoot subs? Enlarge the gas port and/or reduce buffer weight?

Reliability Work:

Gas Port Opened to .120
Gas Tube Port Matched to Gas Block
Bore Scope Alligned Gas Block
Tubb .300 BLK Flat Wire Spring or Reduced Power SpringCo Spring
Extractor Contour & Polish
Carrier Belly Contour & Polish
Matched & Polished Barrel Extension Ramps
Polished Chamber
Carbine Weight Buffer

This all works best with a SLR Adjustable Gas Block in my experience. No other Gas Blocks are worth considering.

As far as a Dissipator Profile, none exist commercially. It will be a custom profile.

9mm does not need a dissipator since it does not use a gas system. As far as proper profiles for adding a FSB, could t say as no one has ever asked.

Wanting a fixed FSB is a good thing. It's more reliable than a rail mounted front sight.

Pistol Gas is more reliable on .300 when Subsonic are used due to the lower pressure of subs.

Chazp89 · Oct 20, 2017

clandestine said:
Reliability Work:

Gas Port Opened to .120
Gas Tube Port Matched to Gas Block
Bore Scope Alligned Gas Block
Tubb .300 BLK Flat Wire Spring or Reduced Power SpringCo Spring
Extractor Contour & Polish
Carrier Belly Contour & Polish
Matched & Polished Barrel Extension Ramps
Polished Chamber
Carbine Weight Buffer

This all works best with a SLR Adjustable Gas Block in my experience. No other Gas Blocks are worth considering.

As far as a Dissipator Profile, none exist commercially. It will be a custom profile.

9mm does not need a dissipator since it does not use a gas system. As far as proper profiles for adding a FSB, could t say as no one has ever asked.

Wanting a fixed FSB is a good thing. It's more reliable than a rail mounted front sight.

Pistol Gas is more reliable on .300 when Subsonic are used due to the lower pressure of subs.

Thank you, I guess my next question would be, I have a 300 aac bull barrel, where could I get someone to turn it down to a profile to fit my needs and re Park it?

clandestine · Oct 20, 2017

Chazp89 said:
Thank you, I guess my next question would be, I have a 300 aac bull barrel, where could I get someone to turn it down to a profile to fit my needs and re Park it?

I can do the countoring but I don't do parkerizing.

ADCO can do the turning down to .750 and the repark job. They do mail order work.

If you need a FSB installed and taper pinned after the work is done, I can do that if you are interested.

outrider58 · Oct 20, 2017

clandestine said:
I can do the countoring but I don't do parkerizing.

ADCO can do the turning down to .750 and the repark job. They do mail order work.

If you need a FSB installed and taper pinned after the work is done, I can do that if you are interested.

This is the man you want on the job Chaz. :thumbsup:

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