Gas system length

[Shotgun Scully]

I've been looking at barrels and found several I'm interested in. But I'm not sure how performance changes based upon gas system length.
I've seen them advertised as Carbine length, Mid length and Rifle length.

Really interested in the 16" rainier arms polyagonal rifled match select barrel in 5.56. It has a mid length gas system.

Thoughts?

 

[soloman02]

I personally prefer a mid length system on a 16" barrel. For me the preference is the look (more handguard covers the barrel). However there is a slight reduction in recoil, not that there is much recoil on a 556 platform to begin with...

 

[jasons]

I've been looking at barrels and found several I'm interested in. But I'm not sure how performance changes based upon gas system length.
I've seen them advertised as Carbine length, Mid length and Rifle length.

Really interested in the 16" rainier arms polyagonal rifled match select barrel in 5.56. It has a mid length gas system.

Thoughts?

That is the "correct" gas system length for a 16" barrel.

 

[Supermoto]

For a 16'', I'd recommend a mid-length. It will be smoother and easier on parts when it has the correct port size

 

[Baystatesuks]

Mid-length would be better than carbine on a 16" barrel. I have a 16" barrel with a carbine gas tube and it's probably overgassed. It works fine but a mid length would likely be better. I use an H2 buffer and haven't had any issues with it.

 

[Lord0fWar]

mid length over carbine length. Slows the guns action down for smoother, more consistent and reliable function

 

[Wrench75]

I have a similar question. Can you get a mid-length gas system on a 10.5in barrel or is it just too short? I was thinking of taking a 10.5 and permanently attaching a muzzle device that, when mounted, adds 6.25 in to the barrel. Ending up with a 16.25 in. barrel with a mid length gas system. So basically my question is, can this be done and would there be any drawbacks having to do with the barrel length? Oh also, I was planning on a 1/8 twist but should I go with 1/7 or 1/6.5 to really "spin up" the bullet since the rifled part of the "barrel" is so short?

For the record, I don't think this is really thread jacking since the questions I am asking are on topic with the OP, except for the twist rate question. If it is however then just let me know and I'll start a new thread.

 

[mav]

Colt M4 with 14.5" barrel uses carbine length gas system. As others have said, if 16" barrel, go mid-length gas system if possible. If 14.5" + 1.5" muzzle device, carbine gas length is fine.

I've got a 16" barrel with a carbine gas system... added an H2 heavy buffer and PWS brake and recoil and action are perfect. Granted it's a S&W, so it's over-gassed from the factory, which just means more wear and tear on the internals. Replacing springs sooner will be necessary.

 

[jasons]

I have a similar question. Can you get a mid-length gas system on a 10.5in barrel or is it just too short? I was thinking of taking a 10.5 and permanently attaching a muzzle device that, when mounted, adds 6.25 in to the barrel. Ending up with a 16.25 in. barrel with a mid length gas system. So basically my question is, can this be done and would there be any drawbacks having to do with the barrel length? Oh also, I was planning on a 1/8 twist but should I go with 1/7 or 1/6.5 to really "spin up" the bullet since the rifled part of the "barrel" is so short?

For the record, I don't think this is really thread jacking since the questions I am asking are on topic with the OP, except for the twist rate question. If it is however then just let me know and I'll start a new thread.

Too short.

The length of the muzzle device is irrelevant as it does not effect dwell time.

 

[Wrench75]

Too short.

The length of the muzzle device is irrelevant as it does not effect dwell time.

I know the muzzle device won't effect the gas system because it isn't sealed. I mainly mentioned it for the twist rate question. So I just looked up dwell time, what I get from it is basically that there would not be enough time between when the bullet passes the gas port and when it gets to the end of the barrel for the gas system to cycle the action. Am I reading this correctly?

Also any opinions about the twist rate? I'm not looking to tackdrive at 500 yds. but I do want to be able to reliably hit man sized targets at 200-300. I just want to make sure the barrel being that short and the bullet going through 6.25 in of a ported muzzle device won't slow the bullet down so much that it gets squirrely after 100yds...

 

[Ink]

I know the muzzle device won't effect the gas system because it isn't sealed. I mainly mentioned it for the twist rate question. So I just looked up dwell time, what I get from it is basically that there would not be enough time between when the bullet passes the gas port and when it gets to the end of the barrel for the gas system to cycle the action. Am I reading this correctly?

Also any opinions about the twist rate? I'm not looking to tackdrive at 500 yds. but I do want to be able to reliably hit man sized targets at 200-300. I just want to make sure the barrel being that short and the bullet going through 6.25 in of a ported muzzle device won't slow the bullet down so much that it gets squirrely after 100yds...

I run a 14.5 barrel with a 1:7 twist, mid length gas system. I can hit small steel at 300 yds with an eotech. The more aggressive twist is better suited to heavier bullets. It can rip apart very light bullets.

Is there a specific reason why you are going with such a short barrel and such a long comp?

 

[mav]

I know the muzzle device won't effect the gas system because it isn't sealed. I mainly mentioned it for the twist rate question. So I just looked up dwell time, what I get from it is basically that there would not be enough time between when the bullet passes the gas port and when it gets to the end of the barrel for the gas system to cycle the action. Am I reading this correctly?

Also any opinions about the twist rate? I'm not looking to tackdrive at 500 yds. but I do want to be able to reliably hit man sized targets at 200-300. I just want to make sure the barrel being that short and the bullet going through 6.25 in of a ported muzzle device won't slow the bullet down so much that it gets squirrely after 100yds...

If you don't want the hassle of an NFA SBR carbine or just want a 16" barrel so longer shots are viable, but want the compactness of an SBR, go with a bullpup like the FS2000, Styr Aug, or Tavor. Personally, if I was going to SBR an AR, I would build a 9mm AR... what's the point of 5.56 in a barrel shorter than 14.5"?

 

[Wrench75]

Is there a specific reason why you are going with such a short barrel and such a long comp?

Purely aesthetic reasons. I just think it would look cool. Basically I just want to keep it compact. The idea was to cover the actual barrel completely with the hand guards leaving just the MD exposed. It is one of the MDs with holes drilled down 4 sides w/ a hole roughly every 1/2in or so.

If you don't want the hassle of an NFA SBR carbine or just want a 16" barrel so longer shots are viable, but want the compactness of an SBR, go with a bullpup like the FS2000, Styr Aug, or Tavor. Personally, if I was going to SBR an AR, I would build a 9mm AR... what's the point of 5.56 in a barrel shorter than 14.5"?

If I could afford one of the decent bulpups out there I would get a PS90 and a FN57 to go with it. It is just not an option.

As for NFA. What is the deal? Is there actually a MG license in Ma. or is it just a matter of getting your CLEO to sign off on the form 4? I KNOW my CLEO won't sign off on it. But if there is no actual license you have to get then I'll just start looking into setting up a NFA trust and my CLEO can go **** himself...

Thanks for the info so far...

 

[mav]

If I could afford one of the decent bulpups out there I would get a PS90 and a FN57 to go with it. It is just not an option.

As for NFA. What is the deal? Is there actually a MG license in Ma. or is it just a matter of getting your CLEO to sign off on the form 4? I KNOW my CLEO won't sign off on it. But if there is no actual license you have to get then I'll just start looking into setting up a NFA trust and my CLEO can go **** himself...

Thanks for the info so far...

I shot Ty@AWS's FN57 and PS90 at last year's car shoot. Loved them both, but the 57 isn't on the MA approved roster so good luck getting one in this commie state. And you'll need more good luck finding ammo to feed it. The PS90 was dope, but ammo is expensive and difficult to find and what's the point as you can't get pre-ban hi-cap mags for it. That rifle and 10 rounds just doesn't sound fun given the price point.

I opted in on the Tavor group buy as it's a cool as heck bullpup in 5.56 and takes standard AR mags. Price is less than what I've seen FN PS90's and FS2000's go for.

MA does have an MG license, but good luck getting it if you aren't a dealer/manufacturer/bona fide collector. The SBR is just a matter of getting CLEO approval and paying the tax stamp, no additional license as far as I know. I think an NFA trust should solve the CLEO approval obstacle.

 

[Wrench75]

I shot Ty@AWS's FN57 and PS90 at last year's car shoot. Loved them both, but the 57 isn't on the MA approved roster so good luck getting one in this commie state.

They can be had but are pricey...

And you'll need more good luck finding ammo to feed it. The PS90 was dope, but ammo is expensive and difficult to find and what's the point as you can't get pre-ban hi-cap mags for it. That rifle and 10 rounds just doesn't sound fun given the price point.

I hear ya. I wouldn't own anything in 5.7 unless I was reloading. As for mags. It is what it is. I don't plan on being in Ma for more than 1 more year so I won't let it determine what guns I buy based on mag cap since I will be moving to a free state.

MA does have an MG license, but good luck getting it if you aren't a dealer/manufacturer/bona fide collector. The SBR is just a matter of getting CLEO approval and paying the tax stamp, no additional license as far as I know. I think an NFA trust should solve the CLEO approval obstacle.

I would imagine that having a 03FFL could help with the bona-fide collector thing. As for the trust, they don't require fingerprints, photos or CLEO signature. Maybe I'll just go that route and do a SBR build. It is going to depend on how much the legal costs of opening the trust turn out to be.

 

[soloman02]

They can be had but are pricey...



I hear ya. I wouldn't own anything in 5.7 unless I was reloading. As for mags. It is what it is. I don't plan on being in Ma for more than 1 more year so I won't let it determine what guns I buy based on mag cap since I will be moving to a free state.



I would imagine that having a 03FFL could help with the bona-fide collector thing. As for the trust, they don't require fingerprints, photos or CLEO signature. Maybe I'll just go that route and do a SBR build. It is going to depend on how much the legal costs of opening the trust turn out to be.

Since you said you are moving to a free state in the near future here is what I would do: Build it how you want and exclude the stock. You for all intents and purposes have a pistol. Then apply for the SBR form 4 with CLEO sign off (most NH CLEO's are cool about it) and put a stock on when you get the tax stamp.

Or is Mass dumb and doesn't allow you to do that because of weight restrictions on a pistol?

Your best bet is to buy everything (minus the stock) and just not assemble it til you get to NH. That way you don't have to pin the flash suppressor/comp and can attach a suppressor if you want to down the line. IIRC, Mass does not have "constructive intent," only the Feds created that. And in reality, that only applies if you get raided. But the Fed's won't get you for constructive intent if you have no extra stock lying about.

It does mean you can't use it. But hey, consider it a present for when you do move to a Free State

 

[Wrench75]

Ma has all kinds of crazy regs when it comes to ar pistols. IIRC you can't have anything on the barrel that even resembles a hand guard. I think the law words it like, any device designed to protect from heat... or act as a grip... Originally I wanted to build an ar pistol before a rifle just because I think it would be funny to carry one on a sling under my coat... lol But then I started looking at the restrictions here and realized it would just be an ugly bastardized version of an otherwise sweet platform.

I guess I could buy a SBR assembly except for a BCG then just leave the the 2 halves apart while waiting on the form 4. Without owning a BCG I should be covered on not having "a collection of parts that could be assembled blah, blah..."

-------------------------

As for "when I get to NH". Though I love the state and canoe there every year, I'm getting the **** out of NE all together. NC, SC and TX are on the table. It is prob. going to end up being SC since the wife has family there. I would prefer TX or UT, the wife wants nothing to do with UT, but I would rather move sooner than later and TX is way more expensive of a move. So one step at a time I guess...

 

[soloman02]

Ma has all kinds of crazy regs when it comes to ar pistols. IIRC you can't have anything on the barrel that even resembles a hand guard. I think the law words it like, any device designed to protect from heat... or act as a grip... Originally I wanted to build an ar pistol before a rifle just because I think it would be funny to carry one on a sling under my coat... lol But then I started looking at the restrictions here and realized it would just be an ugly bastardized version of an otherwise sweet platform.

I guess I could buy a SBR assembly except for a BCG then just leave the the 2 halves apart while waiting on the form 4. Without owning a BCG I should be covered on not having "a collection of parts that could be assembled blah, blah..."

-------------------------

As for "when I get to NH". Though I love the state and canoe there every year, I'm getting the **** out of NE all together. NC, SC and TX are on the table. It is prob. going to end up being SC since the wife has family there. I would prefer TX or UT, the wife wants nothing to do with UT, but I would rather move sooner than later and TX is way more expensive of a move. So one step at a time I guess...

I am pretty certain all the above states you mentioned don't ban suppressors so you're good