Can't believe this worked

[TonyTheTiger]

Yes, that's a 14.8" barrel with a rifle gas system. I bought it as a cheap experiment just to see how much tinkering it would take to get it running. Turns out the answer is zero tinkering. Just a standard rifle with a low mass carrier, whatever spring and buffer was installed from the factory and a .09 ish gas port. I'm only about 100 rounds deep into it, all either mil spec equivalent or lighter loaded 55gr ammo, and it consistently ejects between 2-3 o'clock and locks back using Pmag 30's, 40's and a D60. I'm not anywhere near trusting it or recommending it for anything besides a range toy, but I am pleasantly surprised.

 

[r.tenorio671]

...nice, the amount of recoil in the vid is practically nil.

IMHO, it kinda looks like one of the BA offerings, albeit the RLGS, I wonder if that is one of the OEM barrels that BA is producing since they partnered up with Aero and the funding backing Aero brought with it?

 

[TonyTheTiger]

Yeah the contour is definitely reminiscent of the BA Hanson.
Recoil is pretty light for not having any spring/buffer tuning and only a very mild brake. I can't see an adjustable gas block helping, it's gotta be running borderline undergassed already.
I can't really comment on the exact amount of dot bounce while looking through a scope mount, but it appears minimal.

 

[bfoosh006]

Very interesting, Thank you for sharing.

 

[TonyTheTiger]

Very interesting, Thank you for sharing.

It's different for sure. I've been contemplating how this barrel could work for over two years now, finally gave into my curiosity and bought one.

 

[iOdysseus]

MicroMOA experimented with an angled gas port on a handful of his barrels and realized you can get away with a noticeably smaller gas port size. But he said that it was a PITA to drill the angled gas port.

 

[TonyTheTiger]

MicroMOA went out of business right after I got into AR's, but I do remember them having some pretty unusual lengths, contours and gas system combos.

 

[roostercogburn98]

So a modern take on the dissipator?

 

[TonyTheTiger]

So a modern take on the dissipator?

My understanding of dissipators is that they are 16" rifle gas barrels. I have two of those and they work great, but this being a 14.8" barrel makes it quite a bit less likely to function because of it's extremely short dwell time.

 

[RUTGERS95]

speaking of dissy, I need to build one now

this post has gotten me the bug

 

[black max]

Do you think it would run with a standard weight carrier? I do not.

 

[bfoosh006]

It's different for sure. I've been contemplating how this barrel could work for over two years now, finally gave into my curiosity and bought one.

Your post has piqued my interest as well... from what I can tell, the barrel uses a "normal" gas block ? ( Which begs to ask the question... would an angled gas block help more ? )

I can't help but wonder how much the angled gas port helps felt recoil v. a gas port size "tuned" for "mild" cyclic operation.

That comment is not intended to imply angled gas ports don't work / help felt recoil and allow for less pressure dwell time.

I have always felt gas port size's could be better optimized, or at the very least more carefully chosen for a specific barrel length and gas system length being used.... and the intended use of the AR. And most certainly, I think that in context to Large Frame AR's.

If, I had the time and money, I'd love to do a "Filthy 14" abuse test with a barrel just like this ( Last total round count was 67,500 ? and no cleaning )
I am super curious how "sluggish" it could get and still run.

Years ago..... when dirt cheap surplus 5.56 roamed the Earth...
I tried a Colt 20" HBAR barreled RLGS with as heavy rifle length buffer weight possible , with a Tubbs CWS 4.2oz setup added to the BCG, and a Tubbs 5.56 Flatwire recoil spring... I couldn't get it to choke on any brass cased ammo, even PMC Bronze 55gr. ( Never been a fan of steel cased 223 ) And granted I didn't try it in cold temps... but I was surprised the heavy weighted reciprocating mass just kept on running.

I realize my comment is an "Apples to Oranges" thing to your tested barrel and firearm setup, but it does show, between your setup and mine, how versatile the AR platform can be.

I might have to buy a 14.8 Siphon AGP and abuse it mercilessly.

Again Thanks for sharing.

 

[MontanaMan]

I'm not too surprised............might be fully optimum because of the shorter dwell time, but it looks pretty cool.

You're on the cutting edge.

MM

 

[MK20]

Freeze your ammo overnight and test with chilled ammo to simulate winter conditions. I would be interested to see how it handles cold powder.

 

[D̷e̷v̷i̷l̷D̷o̷c̷A̷Z̷]

So a modern take on the dissipator?

I was about to make a similar comment.


kids just now learning about the dissipator?

 

[TonyTheTiger]

Do you think it would run with a standard weight carrier? I do not.

One way to find out. I'll try it by this weekend.

Freeze your ammo overnight and test with chilled ammo to simulate winter conditions. I would be interested to see how it handles cold powder.

Will do. If it runs with a full mass carrier and it runs with frozen ammo I'll try it with both of those things simultaneously.

 

[TonyTheTiger]

Your post has piqued my interest as well... from what I can tell, the barrel uses a "normal" gas block ? ( Which begs to ask the question... would an angled gas block help more ? )

I can't help but wonder how much the angled gas port helps felt recoil v. a gas port size "tuned" for "mild" cyclic operation.

That comment is not intended to imply angled gas ports don't work / help felt recoil and allow for less pressure dwell time.

I have always felt gas port size's could be better optimized, or at the very least more carefully chosen for a specific barrel length and gas system length being used.... and the intended use of the AR. And most certainly, I think that in context to Large Frame AR's.

Yes, it uses a normal gas block. I'm not convinced the angled gas port helps with recoil, most of the companies marketing is pretty hyped up and gimmicky. But since it's angled towards the chamber it does lengthen the dwell time by .3 or so. I bet that goes a long way towards helping it to function.

Years ago..... when dirt cheap surplus 5.56 roamed the Earth...

I tried a Colt 20" HBAR barreled RLGS with as heavy rifle length buffer weight possible , with a Tubbs CWS 4.2oz setup added to the BCG, and a Tubbs 5.56 Flatwire recoil spring... I couldn't get it to choke on any brass cased ammo, even PMC Bronze 55gr. ( Never been a fan of steel cased 223 ) And granted I didn't try it in cold temps... but I was surprised the heavy weighted reciprocating mass just kept on running.

I realize my comment is an "Apples to Oranges" thing to your tested barrel and firearm setup, but it does show, between your setup and mine, how versatile the AR platform can be.

Yeah it's pretty interesting to try things that conventional wisdom insists won't work. I've tried enough odd combinations at this point I'm often baffled at how many mil spec type home builds won't run.

 

[roostercogburn98]

My understanding of dissipators is that they are 16" rifle gas barrels. I have two of those and they work great, but this being a 14.8" barrel makes it quite a bit less likely to function because of it's extremely short dwell time.

Original dissy was a 20 inch barrel cut back to 16 inches and leaving the gas block in place as was

 

[deersniper]

Wouldn’t having longer gas systems/ gas block closer to end of barrel be better for those of us that run suppressed 100% of the time ?

 

[MK20]

Yes, all things else being equal

 

[roostercogburn98]

My understanding of dissipators is that they are 16" rifle gas barrels. I have two of those and they work great, but this being a 14.8" barrel makes it quite a bit less likely to function because of it's extremely short dwell time.

How do you think a piston would change the way it ran? Shouldn’t that work a little better with a short dwell time since the op system is close to gas port?

 

[bfoosh006]

Yeah it's pretty interesting to try things that conventional wisdom insists won't work. I've tried enough odd combinations at this point I'm often baffled at how many mil spec type home builds won't run.

You said it ! Some of home builds, failing to function, truly makes me wonder as well.

On the other hand ... I have seen threads where the gas tube was installed backwards...

 

[TonyTheTiger]

Wouldn’t having longer gas systems/ gas block closer to end of barrel be better for those of us that run suppressed 100% of the time ?

Yes. I suspect that was part of the intention behind the design. I know Faxon has an 11.5" mid gas barrel designed specifically for suppressed use, and it has very similar dwell time.

How do you think a piston would change the way it ran? Shouldn’t that work a little better with a short dwell time since the op system is close to gas port?

I kinda think so, my brain tells me that the gas can impart sufficient energy to a piston very close to the gas port a lot faster than it can pressurize a 12" tube and get to the gas key. And there are a lot of vintage military semi autos with the gas port near the muzzle. If anyone has a rifle length piston system lying around I'd be happy to test it, unless I eventually get curious enough to spend the $300+ they cost.

 

[TonyTheTiger]

On the other hand ... I have seen threads where the gas tube was installed backwards...

 

[Yondering]

Will do. If it runs with a full mass carrier and it runs with frozen ammo I'll try it with both of those things simultaneously.

Need to freeze the rifle as well if you want to really simulate winter. It does make a noticeable difference; just freezing the ammo is not enough, and is just something gunwriters started because it was more convenient than doing it right.

Ive been pretty surprised at some of the differences from cold soaking the entire gun (with the mag of ammo), sometimes the opposite effect than what I expected. It also highlighted a few instances where the rifle didn’t work because of a line issue. If your firing pin and channel are lubed, clean them out before freezing the gun.

 

[TonyTheTiger]

Hmmm...
The wife might give me a funny look when she finds a rifle in the freezer, but I'm used to that.

I've definitely run into problems with lubricants below 10 degrees. Lucas Oil turned into a paste.

 

[Marc1776]

2-3 o’clock ejection trajectory doesn’t indicate undergassing if anything it’s a little overgassed. Undergassed would be past 4 o’clock.
Let us know if it locks open on empty with frozen rounds. If it does, and ejection trajectory is still “north” of, or at, 3 o’clock, it’s good to go!
Edit to correct effing autocorrect…

 

[Yondering]

Hmmm...
The wife might give me a funny look when she finds a rifle in the freezer, but I'm used to that.

I've definitely run into problems with lubricants below 10 degrees. Lucas Oil turned into a paste.

Yeah, same with my wife. Fortunately our deep freezer fits a full size AR, and I just warn her before she opens it.

 

[DavidAR10]

Yeah, same with my wife. Fortunately our deep freezer fits a full size AR, and I just warn her before she opens it.

Yeah, but what does she say about -10F lubricants?



Takin' up freezer space.

 

[Fred @ Bison Tactical]

As an aside, I run one of these as well, love it and it shoots pretty good. I haven't had any problems running with different carrier weights.

 

[Marc1776]

I use MGL for all my guns, but more especially in the AR platform. Pour point of -50 deg F, and good for 650+ deg F: https://www.sprinco.com/mgl.html

 

[bfoosh006]

Need to freeze the rifle as well if you want to really simulate winter. It does make a noticeable difference; just freezing the ammo is not enough, and is just something gunwriters started because it was more convenient than doing it right.

Ive been pretty surprised at some of the differences from cold soaking the entire gun (with the mag of ammo), sometimes the opposite effect than what I expected. It also highlighted a few instances where the rifle didn’t work because of a line issue. If your firing pin and channel are lubed, clean them out before freezing the gun.

I also would certainly get a funny look ( and comment ) from the wife.

Maybe for fun I will text her and ask her to pull the rifle from the freezer.... and wait for the mayhem.

 

[TonyTheTiger]

2-3 o’clock ejection trajectory doesn’t indicate undergassing if anything it’s a little overgassed. Undergassed would be past 4 o’clock.
Let us know if it locks open on empty with frozen rounds. If it does, and ejection trajectory is still “north” of, or at, 3 o’clock, it’s good to go!
Edit to correct effing autocorrect…

I guess I shouldn't say undergassed, it clearly has enough gas to function. I should say that the dwell time is probably on the very edge of being long enough, and any shorter it would be out of time.

 

[TonyTheTiger]

As an aside, I run one of these as well, love it and it shoots pretty good. I haven't had any problems running with different carrier weights.

How many rounds through it? Any cold weather or extremely dirty use?

 

[sinister]

Tony, I think you've found a very nice "Sweet spot."

Just by your short video it obviously cycles well, without choking (based on a single magazine). Once you've run 500 rounds through it, I think you can definitively say, "Yeah, it works."

Your "Dwell spot" isn't much different than a 633/733 short Commando.

 

[roostercogburn98]

Yes. I suspect that was part of the intention behind the design. I know Faxon has an 11.5" mid gas barrel designed specifically for suppressed use, and it has very similar dwell time.

I kinda think so, my brain tells me that the gas can impart sufficient energy to a piston very close to the gas port a lot faster than it can pressurize a 12" tube and get to the gas key. And there are a lot of vintage military semi autos with the gas port near the muzzle. If anyone has a rifle length piston system lying around I'd be happy to test it, unless I eventually get curious enough to spend the $300+ they cost.

I’ve got one coming if ups ever figures out how to deliver a package. Maybe worth seeing if it runs, just might have to look for a barrel.

 

[TonyTheTiger]

Tony, I think you've found a very nice "Sweet spot."

Just by your short video it obviously cycles well, without choking (based on a single magazine). Once you've run 500 rounds through it, I think you can definitively say, "Yeah, it works."

Your "Dwell spot" isn't much different than a 633/733 short Commando.

What barrel/gas length are those?
Just did some measuring, my 15" intermediate barrel has 3.5" ish dwell length, 16" rifle is about 3.2", 10.5" carbine is 2.8". My 12.8 mid is out for cerakote so I can't measure it. Didn't measure the 13.7, 14.5 or 18" rifles. All that to say this 14.8" rifle gas has 1.8" of dwell time, on the OD of the barrel, probably 2.1" ish on the interior because of the angled port.

 

[sinister]

GI 633/733s are carbine-length gas system (7-inch fore-ends):

 

[Ravenworks]

A lot of Criterions also use rifle length gas systems

 

[TonyTheTiger]

GI 633/733s are carbine-length gas system (7-inch fore-ends):

View attachment 7730561

So very similar to my setup. I've noticed that very short barrels with short dwell time seem to be common and more accepted than longer ones. I wonder how much the higher port pressure helps them run vs. the significantly lower port pressure of a rifle gas system.

 

[Fred @ Bison Tactical]

How many rounds through it? Any cold weather or extremely dirty use?

I shot a lot of handloads through it (maybe 500-1000), ran it is weather but nothing extreme. I ran it for 3 days at the Steel Safari train-up put on by Brian Whalen, its talked about a bit in my blog post on the course:

2021 Steel Safari Train-Up - Bison Tactical - Colorado Precision Rifle

Click here to read about my experience at the 2021 Steel Safari train-up put on by Colorado Precision Rifle's Brian Whalen

www.bisontactical.com

I ended up using a longer barrel mostly for higher velocity gains for the Steel Safari, but not because this barrel was a problem, I just wanted more velocity for longer targets.

 

[sinister]

The M1 rifle is proof you can put the gas port towards the muzzle. You don't need a ton of gas to move the bolt carrier group and buffer:

 

[TonyTheTiger]

14 hours in the freezer. With ammo the way it is I didn't test cold rifle/ammo and full mass carrier separately, figured I'd just go big or go home and do both simultaneously. Didn't clean the oil out of anything either, it's pretty well lubed. Shot two magazines of twenty rounds each, it was plenty warm after forty rounds so no point in shooting more. Ejection pattern was more erratic.

 

[sinister]

Military and NATO testing is done to EPVAT standards.

This test is performed under normal conditions at 21 °C (70 °F), but also by simulating cold polar −54 °C (−65 °F) or hot desert 52 °C (126 °F) conditions using special cooling equipment and ovens to cool or heat the ammunition under test to the appropriate levels of humidity and temperatures required.

"Electronic Pressure Velocity and Action Time". Action Time here means the (short amount of) time required between the ignition of the primer and the projectile leaving the barrel. This is a comprehensive procedure for testing ammunition using state-of-the-art instruments and computers. The procedure itself is described in NATO document AC/225 (Com. III/SC.1)D/200.

Unlike the C.I.P. procedures aiming only at the user's safety, the NATO procedures for ammunition testing also includes comprehensive functional quality testing in relation with the intended use. That is, not only the soldier's safety is looked at, but also his capacity to incapacitate the enemy. As a result, for every ammunition order by NATO, a complete acceptance approval on both safety and functionality is performed by both NATO and the relevant ammunition manufacturers in a contradictory fashion.

 

[TonyTheTiger]

Took it to a match yesterday. 200 ish rounds in 20 degree temps before windchill. So that puts this gun at almost 1k rounds in only winter conditions with no cleaning and zero malfunctions. I'm pleasantly surprised.

 

[bfoosh006]

Took it to a match yesterday. 200 ish rounds in 20 degree temps before windchill. So that puts this gun at almost 1k rounds in only winter conditions with no cleaning and zero malfunctions. I'm pleasantly surprised.

I love it when things work... and some how defy what shouldn't work.

Sometimes.... book smart isn't real world experiences.

 

[TonyTheTiger]

I love it when things work... and some how defy what shouldn't work.

Sometimes.... book smart isn't real world experiences.

Me too. I figure since I'm always on here championing longer than average gas systems I should put my money where my mouth is and see what is possible.
I've got a 17" rifle +1" barrel on order for my next unconventional experiment.

 

[TonyTheTiger]

Did get video of one of the smaller stages Saturday. Takeaways are that it's not as soft or flat as a full tilt race gun, but that makes sense. The light barrel profile definitely keeps the front end agile. Probably won't shoot it again in a match just because it gives up a bit to my more well tuned guns, but it was cool to see it could work if I wanted it to.
Don't mind the falling apart stage walls, nothing was holding up to the 35mph gusts well. If the shooting looks slow it's because it was a hit factor scored match so I turned it down a notch to shoot A's.

 

[WindstormSCR]

sent this link over to a friend who is a big fan of dissipators but loves the length of the standard M4, and he's already ordered all the parts

Good stuff, and thank you for the testing, seems Siphon AGP has a very solid product to run that well when intentionally put in bad conditions

 

[TonyTheTiger]

Good stuff, and thank you for the testing, seems Siphon AGP has a very solid product to run that well when intentionally put in bad conditions

Can't remember if I mentioned it above or not, but I have one of the 16" AGP's also, in my dead barrel pile. I think it went 11-12k before accuracy became unacceptable. Not that it was ever a Bartlien, but they seem to shoot pretty well across my two AGP samples.