Can we talk AR15 gas systems?

[gun_slinger_boy]

Ok so I had no idea this was a thing until recently but does anyone have any experience with carbine length barrels with rifle length gas systems? Or in other words a barrel with the gas port closer to the muzzle. In my head it would seem that this would make the recoil lighter due to less dwell time, burn more powder before reaching the gas port therefore seeing slight velocity increase and cleaner shooting.

We know that the typical 16inch barrel uses a carbine length gas system for reliability with under powered ammo or dirty conditions. So I'm wondering if using a carbine barrel with a rifle gas system would make it dramatically less unreliable. Would you have to possibly load up hotter ammo, play with the buffer weight/spring or combination of both? This almost seems like a no brainer but I know there's gotta be a reason that it's not more common.

 

[ArmedCorgi]

Ok so I had no idea this was a thing until recently but does anyone have any experience with carbine length barrels with rifle length gas systems? Or in other words a barrel with the gas port closer to the muzzle. In my head it would seem that this would make the recoil lighter due to less dwell time, burn more powder before reaching the gas port therefore seeing slight velocity increase and cleaner shooting.

We know that the typical 16inch barrel uses a carbine length gas system for reliability with under powered ammo or dirty conditions. So I'm wondering if using a carbine barrel with a rifle gas system would make it dramatically less unreliable. Would you have to possibly load up hotter ammo, play with the buffer weight/spring or combination of both? This almost seems like a no brainer but I know there's gotta be a reason that it's not more common.

Why not just go for an adjustable gas block?

 

[Podmonkey]

I don't think a rifle length gas system will fit on a 16" barrel. I've never seen such offered for sale anyway. The mid length gas has become standard for 16" barrels. The mid length can also be had on 14.5" barrels now. 18" barrels cam, and do, fit the rifle length gas however the top tier gas have introduced the intermediate length which sits between the mid length and rifle length. For a 16" barrel just get the common mid length, works fine.

 

[Eddie Gunks]

You need a few inches of barrel ahead of the gas hole for it to function reliably.

Thatbis why the original (well now i cant remmeber the name of this) barrels that were 20 and the cut them way daown did not run reliably......too close to the gas hole.

The fix to the problem was to make a crbine gas system. This way they were able to run shorter barrels.

This is also what they say 11.5 is the shortest to go if your life relies on it. I know they have 7.5 with pistol gas but some have reliablity issues. None of the 7.5 i have build had any troubles, but to be fair i never ran 3-4000 rounds or more through them.

I noticed a recoil impulse difference in rifle vs carbine. I can not really feal much in carbine vs. mid. IMO none really recoil appreciably anyway.

 

[BDinPutnam]

@Eddie Gunks are you thinking of the dissapators (sp?)?

I've never really understood the point of them but never researched either.

 

[Eddie Gunks]

@Eddie Gunks are you thinking of the dissapators (sp?)?

I've never really understood the point of them but never researched either.

Yes. That is it. Thanks

 

[togmaster]

There are also midlength gas, which I own. Works great on a 16" barrel.

 

[Podmonkey]

Here is a good article on the topic:

What is an AR-15 Dissipator? - Pew Pew Tactical

And I concur with their conclusion.

@gun_slinger_boy, just get a middy and if you want extra room on the handguard there are all kind of extended free float guards available.

 

[meketrefe]

The M4 style barrels and carbine porting should have never existed. It was put there along with the stupid slot
to allocate the grenade launcher bracket and all was a big mistake.

Carbine barrel runs more reliable in a mid-port in any situation.
Anything 18 inches and above works great with the rifle porting.

One eliminates the spikes and valleys and controls a more uniform curve because the ports are larger.
So you have a less aggressive but more consistent push over the gas group.

I have cut them in all sort of shapes and forms and double porting and what I say are the facts.

What one has to do is to port them properly with the same tolerances top barrel makers use and
avoid gas leaks. for this reason stick to clamp steel blocks only and make sure the keys are well
made too up to spec and tubes are flared accordingly.

The porting is the easiest part of the whole gas tango.

 

[gun_slinger_boy]

Here is a good article on the topic:

What is an AR-15 Dissipator? - Pew Pew Tactical

And I concur with their conclusion.

@gun_slinger_boy, just get a middy and if you want extra room on the handguard there are all kind of extended free float guards available.

I'm actually going to free float my AR and in my research of which handguards to get I went down a rabbit hole. The company I'm getting the handguards from also make carbine length barrels with the rifle length gas system. A carbine length barrel has more than enough space for a rifle length gas system as the gas tube is 12 inches long. That's 5 inches more down the barrel than the carbine length and 3 inches more than the mid length. I'm guessing the intermediate length is either 1o or 11 inches long. At that point I feel you may as well go all the way.

I think something else to consider as well is suppressor use. Doing it enough makes my eyes tear up because of the added back pressure with an already over gassed rifle. I'd think in addition to getting less blowback it would also keep the rifle cleaner for longer when using a can. Here is one of the companies (Foxtrot Mike) that offers this type of barrel.

New! FM Products Premium 41V50 5.56 AR Barrel Up to $10.00 Off w/ Free Shipping — 2 models

 

[meketrefe]

1/2" threads in the muzzle is another mistake.
The crown sells over time specially with shorter barrels and heat.
It has nothing to do with the section but they cannot be stressed relieved after cutting and threading because
of obvious reasons. 5/8 threads is a much better choice.
I have started to do 3/4 in some barrels or just pinned & then threaded sleeves.

 

[gun_slinger_boy]

The M4 style barrels and carbine porting should have never existed.

Carbine barrel runs more reliable in a mid-port in any situation.
Anything 18 inches and above works great with the rifle porting.

Do you know the reason for this? Is it because the 2 to 4 inches of extra barrel and longer dwell time allow more gas to go back through the tube before it all spews out the muzzle?

ETA here is one of these barrels in action.

 

[meketrefe]

Do you know the reason for this? Is it because the 2 to 4 inches of extra barrel and longer dwell time allow more gas to go back through the tube before it all spews out the muzzle?

ETA here is one of these barrels in action.

The reason is simple, the larger port allows more gas through but it is past the point of spikes in hot loads or valleys in mild loads
so it is more uniform and constant. Compare a garden hose with a jet from an electric power washer given faster or slower pulses.
To the point the carbine can rupture cases in hot loads (too much gas) and malfunction with certain super light varmint loads.

you should not have those problems with the longer porting and as you get further the port becomes larger but thee is no risk
to go a few thousands even larger from reliability because it will never provide the type of spike in preassure a hot load
can put in a short port.

The closer you get to the chamber the higher is the pressure so any minute differences in the porting are more critical
and therefore harder to balance or make it reliable for all sort of loads.

Plus the gas group runs much hotter and the bolt too. Ahead of the gas block is a known point of failure with M4 style
barrels and carbine ports if one pushes them to the limit. They can be used and adopted with careful selection of
parts but I have no idea why civilians keep buying this crap when you have amazing mid size barrels w/o the stupid
and useless slot that only makes the barrel weaker.

Make the port even shorter and you are torching the group unless one goes with a short
stroke piston system.

It is not like civilians are going to install a grenade launcher I would say.

Typical army bull crap by screwing a perfectly good barrel vs. redesigning the launcher's bracket.

 

[Jem45472]

I believe most dissipators sold in 16" used a low profile gas block at mid length gas, then a non-functional sight post up where rifle length gas port would be.

 

[Jem45472]

What is an AR-15 Dissipator? - Pew Pew Tactical

 

[meketrefe]

I believe most dissipators sold in 16" used a low profile gas block at mid length gas, then a non-functional sight post up where rifle length gas port would be.

If it is not a rifle porting then it is not a "dissipator" original denomination.

There is another length for the port position that is between the rifle and mid that is not very popular. I have a 6x45 upper in that one that is amazing
but finding the gas tubes is a bitch. I can cut one rifle and flare it because I have the tools but most people should look into the mid or rifle no matter
what rifle barrel size.

We have been saying this for years that the M4 tacticool style barrels are stupid form the engineering stand point.
Carbine porting, minor diameter too small and 1/2" threads all mistakes from the past.

Mid/Rifle porting, larger profile ahead of the chamber, 3/4" smallest possible minor diameter anywhere in the barrel and 5/8 threads, that
is the way to go. I know barrels are cheap but some sell the above and already nitro-carburized (melonite) and they are not
much more money given all the benefits. Even if they are 200 over 100 dollars is that really relevant given the added reliability
for the entire service life of that barrel?

I mean, most people will do fine with an M4 tacticool budget barrel but the best options one can buy are not going to be those.

 

[gun_slinger_boy]

There is another length for the port position that is between the rifle and mid that is not very popular. I have a 6x45 upper in that one that is amazing
but finding the gas tubes is a bitch. I can cut one rifle and flare it because I have the tools but most people should look into the mid or rifle no matter
what rifle barrel size.

I talked about this in an earlier post and maybe things have changed since you last looked but I simply typed in "intermediate gas tube" into google and a whole bunch of companies come up. NOVESKE, Odin Works, Wilson Combat, Raineire Arms, Lantac USA etc. So what would be the reasoning for getting a gas system that is between 9 and 12 inches? Seems like it would be a rifle/caliber that has to be meticulously tuned.

 

[meketrefe]

I talked about this in an earlier post and maybe things have changed since you last looked but I simply typed in "intermediate gas tube" into google and a whole bunch of companies come up. NOVESKE, Odin Works, Wilson Combat, Raineire Arms, Lantac USA etc. So what would be the reasoning for getting a gas system that is between 9 and 12 inches? Seems like it would be a rifle/caliber that has to be meticulously tuned.

There is no good reason. Several makers started experimenting with different things in order to provide something "better" for the 18" barrels but the
fact is that 18" run like a dream with rifle port just like the 16" ones if they are ported accordingly. Even if one puts a bit more meat on the barrel
that is almost negligible weight different can run them with a M16/national match style carrier and nylon buffer w/o problems.

So be weary of the latest greatest thing as most times is all snake oil salesman. Marketing is a powerful force. That is how we ended up with the blackout fashion as well.

 

[Podmonkey]

I really don't see why why you wouldn't just get the standard midlength gas. Runs wonderful.
I can understand wanting to scratch a particular itch but why overcomplicate things?

 

[gun_slinger_boy]

I really don't see why why you wouldn't just get the standard midlength gas. Runs wonderful.
I can understand wanting to scratch a particular itch but why overcomplicate things.

I'd say because if going from a 7 inch system to a 9 inch system makes a difference so will going from a 9 to a 12. If the port hole is the right size which it seems these barrel manufacturers have figured out for the 16 inch barrel why not? I'd mostly like to see how it works on a can. Since the dwell time is less more gas is going to go into the can instead of back into the action. I would think this would mean less mace effect and quieter at the shooters ear. And that's the whole point of a can.

ETA I don't think this is complicated but just different

 

[Podmonkey]

I'd say because if going from a 7 inch system to a 9 inch system makes a difference so will going from a 9 to a 12. If the port hole is the right size which it seems these barrel manufacturers have figured out for the 16 inch barrel why not? I'd mostly like to see how it works on a can. Since the dwell time is less more gas is going to go into the can instead of back into the action. I would think this would mean less mace effect and quieter at the shooters ear. And that's the whole point of a can.

ETA I don't think this is complicated but just different

I have been peepin' them OSS Helix suppressors.
It's a baffleless can, manufacture claims that their is much less back pressure induced. I wonder if there is anything to that?

 

[gun_slinger_boy]

I have been peepin' them OSS Helix suppressors.
It's a baffleless can, manufacture claims that their is much less back pressure induced. I wonder if there is anything to that?

I saw those a while back. They are described as working like a reverse turbine. A bit louder out of the muzzle but quieter at the ear. And like you said very little blowback. I want to stick to my lowly form 1 can though

 

[meketrefe]

I'd say because if going from a 7 inch system to a 9 inch system makes a difference so will going from a 9 to a 12. If the port hole is the right size which it seems these barrel manufacturers have figured out for the 16 inch barrel why not? I'd mostly like to see how it works on a can. Since the dwell time is less more gas is going to go into the can instead of back into the action. I would think this would mean less mace effect and quieter at the shooters ear. And that's the whole point of a can.

ETA I don't think this is complicated but just different

The benefits of going further away from the chamber are many because it is a DIRECT impingement system.
The only two carbines I have are both piston systems because that is the only way to keep them reliable over sustained rates of fire.
In addition the piston system works pretty much like a regulator and it has 3 positions, full open, suppressed and closed.
I have the same piston in one rifle upper for the sole purpose of shooting closed in long range with a high end match barrel.

Back to the ports, there is no problem with a carbine port on a 11" pistol barrel. The dwell is more than plenty anyway and
will need to open up the port just a couple of those if using very mild ammo like PMC bronze or some of the super light varmint rounds.

If you go with a mid-length port and a 12 1/2 or 13" barrel even better. IMO anything shorter than 13" is a huge waste for any rifle caliber.

 

[gun_slinger_boy]

The benefits of going further away from the chamber are many because it is a DIRECT impingement system.
The only two carbines I have are both piston systems because that is the only way to keep them reliable over sustained rates of fire.
In addition the piston system works pretty much like a regulator and it has 3 positions, full open, suppressed and closed.
I have the same piston in one rifle upper for the sole purpose of shooting closed in long range with a high end match barrel.

Back to the ports, there is no problem with a carbine port on a 11" pistol barrel. The dwell is more than plenty anyway and
will need to open up the port just a couple of those if using very mild ammo like PMC bronze or some of the super light varmint rounds.

If you go with a mid-length port and a 12 1/2 or 13" barrel even better. IMO anything shorter than 13" is a huge waste for any rifle caliber.


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I think I'll give it a whirl. The barrel I posted is $135. Then a gas block and a tube. I figure if it doesn't work I'll just be out about $150. But I don't see why it would fail the more I think about it and with what has been said in this thread.

 

[meketrefe]

I think I'll give it a whirl. The barrel I posted is $135. Then a gas block and a tube. I figure if it doesn't work I'll just be out about $150. But I don't see why it would fail the more I think about it and with what has been said in this thread.

I don't see why it should not work, do you? unless they made a mistake with the port size.
get a steel gas block with strong clamp screws and tight tolerances. Those are the way to go.
you sill have a huge blast so will need a supressor or unless you like fireworks and heat.