Carbine Vs. Mid Length?

[DubC-Thompson]

Looking at buying a spikes tactical ar-15. What is better for a 16" ar... a mid length gas system or Carbine?
-Thanks for the input

[GaryM&P]

mid length

[DanThaMan1776]

Mid length is softer on the rifle, has better sight radius, and is typically more reliable and lasts longer due to being softer on the rifle.

[Technosavant]

Generally, midlength is a better choice. Carbine length was developed for the 14.5" military length barrels. It stuck around because that's what all the accessories were for, but now that midlength has become quite common in the civilian market, accessories aren't an issue.

If availability of the uppers is the same, midlength will be a bit smoother/softer to shoot, so that's what I'd recommend.

[smoakingun]

mid length gives a bit more handguard to grab, and with a 16" barrel, you use a bayonet:D

[DnPRK]

The longer the gas system the better the function/reliability.

Carbines are known to be tempermental if you change ammo manufacturer or at hot or cold temperature extremes.

[Technosavant]

The longer the gas system the better the function/reliability.

Not necessarily, there's several variables in the equation, and it is often treated as though length of the gas system is the only one. It isn't; there's at least two others.

"Dwell time" is a term that often gets thrown out here. That's the time that it takes for the bullet to exit the muzzle once it passes the gas port. ARs tend to prefer dwell time that is similar to the 20" barrel with a rifle length gas system. More dwell time means more pressure and heat in the upper receiver. Less means less, but it also may mean there isn't enough gas to actually cycle the action.

The size of the gas port in the barrel also matters. One can use a setup with a much shorter dwell time by increasing the size of the gas port- you get more gas down the tube, increasing the likelihood that it works reliably. If you're running a short gas system, using a smaller port will reduce pressures, taking some of the energy out of things and making life easier inside the upper receiver.

I have a 18" barrel with a rifle length gas system- technically, it's a bit too little dwell time, but it functions reliably (no failures at all) and very softly since the gas port is (presumably) opened up a tad. I also have a 16" carbine length gas rifle that runs 100%; I'm likewise presuming the maker (BCM) used a slightly smaller gas port to compensate.

So yes, when we talk about "longer = better" and a midlength being ideal for the 16" barrel, it's because we're also assuming the above variables are similar. They aren't always.

[tirod]

Since the military has no obligation to accomodate various loads, it sticks to a gas port size that works with it's primary rounds. If anything, the ammo is designed to work in that envelope, not vice versa. Civilian guns with large ports are mostly to shoot cheap low powered ammo, and when mil spec is shot, have a lot more recoil impulse and harder cycling.

Length of the gas port is measured from the MUZZLE, not chamber. That's why the carbine is the shortest, it's set up for a 14.5" that civilians would have to have registered. The correct length for a 16" barrel is midlength. There are two more, intermediate, for 18", which is a Noveske innovation, and rifle, the original, for a 20".

To amplify even more, some makers offer a long gas tube for the carbine, that wraps around the barrel in an attempt to simulate the longer midlength.

The appropriate length of the gas port is usually 5-7 inches from the muzzle, which is why the civilian carbines aren't carrying a reputation for reliability, especially when a maker opens up the port even more to run cheap plinker ammo. That's where they get a reputation for hammering the bolts and having harsh recoil, which actually isn't as much a problem for M4's. They aren't set up with the wrong dwell.

16" with carbine gas sell alot, but it's the customer who doesn't know better buying them, and the customer always thinks he's right.

[Technosavant]

16" with carbine gas sell alot, but it's the customer who doesn't know better buying them, and the customer always thinks he's right.

I think the 16" carbine sales numbers are trending downward; while they're still pretty popular from the major makers, that seems to be more because that's just what they are making for sale. I don't see many people rolling their own with a carbine length system anymore- midlengths have become far more common and much more available.

It isn't that a carbine length system is bad (when properly set up), it's that a midlength is better for a 16" barrel.

[Ridge_Runner_5]

Midlength:D

http://i17.photobucket.com/albums/b100/89Sunbird/Shooting/DSC_0042.jpg
http://i17.photobucket.com/albums/b100/89Sunbird/Shooting/DSC_0046.jpg
http://i17.photobucket.com/albums/b100/89Sunbird/Shooting/aff3f5f9.jpg

[DubC-Thompson]

does the military issue mid-length rifles? or just carbine length

[smoakingun]

i don't think the military issues a rifle with a 16 inch barrel

[Technosavant]

AFAIK, the barrel length of the M4 is 14.5" or so, and the military does not use 16" barrels. The 16" barrel exists for one reason and one reason only: the 1934 National Firearms Act. Sixteen inches is as short as you can go and retain a non-permanently mounted flash hider or other muzzle device while avoiding a cumbersome paperwork process and a $200 tax.