Even though the difference in gas port location is only 2 inches, which may seem like a very small difference, is enough to cause the port pressure to be reduced to almost half of the carbine port pressure. It is significant.

This really does improve the situation with gas port erosion, and also to some extent helps the timing issues that can plague the carbine system.

Extraction reliability, and overall reliability should increase with a midlength system, over a carbine system.

I don't think the sight radius difference is significant enough to mention, but it is a little bit longer.

With the attendant longer handguards, and the FSB moved forward too, there is a shift of the weight slightly forward, and typically a slight increase in weight because of longer handguards.

At this time, there is a pretty good selection of railed handguards in the midlength size, but for a while it was pretty slim pickings. Still a little sparse on finding gas tubes everywhere for a midlength, but they can be gotten.

What would really be nice, would be if someone would come out with a midlength system that could use all the carbine parts, and still have the midlength advantages.
Maybe somebody will do that soon.

Bomber,
The carbine gas system problems have always been there, but over the years they have been largely solved to the point where it is quite possible to have a very reliable carbine AR15 system.

The things that have not been solved, are the gas port erosion and the timing issues.

Even though there are very good products available to improve extraction in a carbine, and to slow the cycling, the characteristic of trying to extract the round while the pressure in the chambered case is still very high, is still present. The bolt is trying to open early, and the extractor is trying to pull out a case which is being swelled against the chamber wall by high pressure. This is definitely going to increase extraction difficulties.

The new products really can help with this by adding extractor tension, and slowing the bolt opening timing with a heavy buffer.

The other issue is gas port erosion, and that will be increased by higher pressures and heat being forced thru the gas port. This is a slow process, and may take a couple thousand rounds to be really noticeable, but it happens right from the beginning, and slowly erodes. One of the reasons for it not being noticed is that it happens over time, slowly.

The result of an eroded gas port is faster cycling, and more violent action speeds, and battering, as well as bolt bounce, and feeding and extraction issues. Some of the most popular items that MGI makes are specifically to deal with these problem, and they do very well at it.  But the root cause is still there, which is the carbine length gas system.

So, while a user may not experience difficulties with the carbine system, the causes for creating difficulties are all there, and probably will rear their ugly head at some point, even if you gun runs perfect right now. I see comments quite often on threads about this, "My gun runs just fine without that product". But, we're gun designers, and we know that won't be true forever. Eventually, this will become a problem for him, but he doesn't know it yet.


Basically, I alluded to a product in my earlier post, which I felt was a good idea
The idea was to have a midlength gas system, which looks just like a carbine gas system, and allows the use of carbine railed FF tubes, carbine gas tubes, carbine FSB location, and keeps  these standard parts compatibility, but gives midlength gas system to your gun. Saves a small amount of weight by not requiring longer FF tube, and keeps weight more centered for handling.
Essentially, it is a "stealth midlength".

This product should be available starting somewhere between  the end of July, to maybe mid-August.
I'd tell you more about it, but I don't want to spoil the introduction.
I can say that the new FSB which is a required part, will have a flip-up front sight  with adjustability for windage and elevation.
While this new MGI Midlength system will only be available with barrels(as a package) at the  outset, we do plan to make kits available later, to convert your existing carbine barrel to midlength, for a very reasonable sum. In this kit form, it will be by far the cheapest way to have a midlength gas system. And actually, people moving from carbine to midlength systems will be able to do it cheaper now, because they won't be required to get longer handguards or FF tube, even if they do have to buy a new barrel with it.
It's a pretty cool system, if I do say so myself.

Bomber,
Just maybe a week or so prior to release, I will put up some info and some pics of the new MGI Midlength system.

Currently, we are having some specialty barrels made for the package.
At this time, we are planning  high-spec barrels which would have most or all of the currently "hot" features such as M4 ramped barrel extensions, MP tested 4150 steel, Chrome lined, 16" length, 1/7 twist, etc.

The packages will be available 2 ways:
1) Barrel assembly with MGI Midlength gas system and folding FSB
2) Barrel assembly with standard carbine gas system and mil FSB.

Both will fit with carbine handguards.
The barrels will not include barrel nut, delta ring, or handguard keeper, because we are manufacturing them for use with our MGI QCB upper receiver system.
Barrel nuts, delta rings, and handguard keepers will be available separately for user installation, if needed.

Our new flip-up folding FSB is very cool, and has both windage and elevation adjustments, can fold either front or rear,  has a bayo lug, and will be cross-pinned in military fashion. This will only be available on the MGI Midlength system, and the carbine system barrels will have standard "F marked" FSB .

Stormsurge,

You Are Correct.

Doing it this way puts the gas port almost in the exact same place that the "normal" midlengths have, but ours doesn't require special stuff except the gas block/FSB.

The future "kit" will include our new flip-up FSB/gas block and the gas tube w/roll pin, and instructions on how to re-drill your existing carbine barrel to make it a midlength.

We decided to roll-out the initial product as a barrel assembly, because we want to ensure good acceptance into the market, with a package that we know will work.
When you make kits, there is always a chance of somebody screwing up the installation, and we don't want any "user related installation" complaints at the very beginning.
Then the kits will be available after people see how cool this idea is.

Another nice point about this kit will be that if you have a carbine with an eroded gas port, you will get a brand new gas port when you make this mod, and the old one will be plugged, so your gas system will be brand new and not eroded, and a midlength to boot. It's sort of like giving your barrel a "second chance at life".

On chrome-lined barrels that the customer modifies, there will be a chance of having some chrome flake off around the new gas port when it is drilled. We can't help that, and it can happen when you drill a chrome lined barrel. However, the middy port erodes much less slowly, so it shouldn't be a bad problem if there is a little chrome missing around it.  It'll be alot better than having an already severely eroded carbine gas port.
If that is a big concern, we have new barrels made with the new gas port, and you can always buy the full barrel assembly if modifying your barrel bothers you.
As I said, at the beginning, it will only be available as a barrel assembly, with the barrel and flip-up FSB/gas block/gas tube. I don't know how much later the kit will come out.

Availability of these new MGI Midlength barrel assemblies is only a few weeks away now.

I agree with you that this was the "obvious" solution to the midlength problem that seemed to escape the vision of everybody else.  Maximum compatibility with existing units, and minimum fuss. You can't tell that this system is a midlength by looking at it, unless you recognize our very cool new flip-up FSB. Very "stealth".

We'll probably make some lo-pro gas blocks with the MGI Midlength gas port too.

Cvg69,

I guess it depends on an individual's idea of advantages.

I agree that when buying a new gun, it can be configured any way you want, at probably no difference in cost.

When changing a gun over to midlength from a carbine, it may be different in cost, and especially so if you already have bought an expensive railed FF system for your carbine previously, and then have to buy a midlength one when you decide to change. With the MGI system, you could still use your carbine railed-FF system without having to buy another.

Also, for every user who prefers the added weight, barrel coverage by the handguard, additional rail space for options, and added sight radius of the currently available midlength systems, there are some who would prefer lower weight, don't need alot of rail space, use CQB optics(so sight radius is backup only), and don't burn themselves with the barrel anyhow.

In any case, the new gun issue is almost moot, because as I already admitted, there is not going to be any cost issue one way or the other for a new midlength or carbine, so the MGI system would primarily be for those who wanted to add this to their guns, and  the MGI QCB owners who routinely change barrel systems on their weapon. People who have costly carbine rail systems or have a QCB system will have a  lower cost of reconfiguration with this system.

Also, when the kit comes out, it will be possible to reconfigure your existing carbine barrel to a midlength, which is totally not possible with any other system available today.

Regarding the gas tube, we use a carbine gas tube, but it is slightly modified. In a pinch, a user could easily do the mod himself, as we do not add length or any other major changes.

For those who already have midlength systems from other mfrs, I can see that it might not be desirable to change to the MGI Midlength. That is perfectly fine, and they already have what they want.

Nothing is perfect for everyone.
We offer something different, that has its own advantages for the people who need/want it, compared with the other units available elsewhere.

For those wishing to convert a carbine to a midlength, this is a very attractive package, which could be less expensive to do, depending upon the system in question.

If we decide to make military style FSB's with this gas config(which we are contemplating) it would be possible to maintain the true M4 "look" of the barrel/gas system that the M4 has, and still benefit from midlength gas system, which could not be done any other way.

For a conversion kit application to a carbine barrel, this would easily be the least expensive way to get into midlength, since the kit will not require the purchase of a barrel, nor different handguards, and only the FSB and modded gastube would be required for those who install the kit.

Since we will offer various ways to purchase this item in barrel assembly or in kit form, it will add choices to the market for those buyers looking for another way to get to their midlength goals.

Regarding the bayonet, our FSB will have a bayo lug, and will allow use of the bayo on a 14.5" barrel, but not a 16",  just as the carbne systems are now.

It would probably be best for us to return the thread to the normal subject of midlengths in general, but if anyone has questions, I am always available by IM, Email, or Phone.

Back to the top so other who missed it...
and I locked the other.

Well, I guess we'll just have to see what happens.

The pre-production samples are being delivered at the end of this week, and we'll do a good check-over of all the critical stuff, and do some testing to see if they need any changes for the production run. Then it will be available.

How the market accepts this, remains to be seen.

BTW, we do recommend plugging the old gas port first, if a barrel were to be modded for this system. We will make packages available initially, which will include an entire barrel assembly made for this system, so that people don't have to do any mods if they want to use it. The mod kit will come later for those who would prefer to convert their existing barrels.

I think that people who use carbines will like to be able to get midlength benefits without being required to change their handguard.

I suppose the market will show us what they want.

We see a trend toward a shorter and lighter weapon system like a carbine is.
We also see a desire for a more reliable gas system like the midlength type.
This is a move in both of those directions at the same time.
Minimize weight, length, and bulk, and have middy gas benefits in a carbine size package.
I think it will be a winner.

We're going with .084" midlength gas port.

Our carbine length middy system is looking like October now, because Mack got sidetracked on the belt-feed project.  We will see some pre-production units soon, though.

I don't have the figures here in front of me, but I think that Mack has them over at MGI.
IIRC, the port pressure has a quite significant drop over those additional 2 inches.
Pretty sure that is why I made the statement that I did previously.

I'll try to get the port pressure data for you if I can.

Thanks