User Panel
Posted: 7/7/2005 11:08:15 PM EDT
Please forgive my noobness... but what exactly is the definition of a midlength? Is it the handguard or the barrel, or both that makes a midlength a midlength?
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Its the gas system, which is slightly longer than carbine length.
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middy's kick ass...its almost like a dissy but not, and you can put a bayonet on there with no modification or adapters.
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What are the advantages & disadvantages to a midlength compared to a carbine length?
hk45shooter |
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There's an option nobody can live without. |
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From this aritcle: Armalite Mid-Length Carbine and A.R.M.S. Mid-Length S.I.R. System
..."The Armalite Mid-Length Carbine was designed specifically to overcome the long-known gas system-related problems associated with the standard M4/M4A1, problems that have been plaguing end-users for years. These include greatly accelerated gas port erosion, , excess heat, higher operating gas pressures, melted and blown-out gas rings, and an open/iron sight radius that's too short. None of these are good things on a field combat weapon. So, how does the the Mid-Length Carbine mitigate these problems? The Mid-Length Carbine moves... the front sight base/gas block 2 inches forward from its position on the M4/M4A1 Carbine. This puts the Armalite Mid-Length Carbine's gas port mid-length between that of the M4/M4A1 carbine and full-length AR-15/M16 rifle, thus the Mid-Length Carbine's name. The 20-inch barrelled AR-15/M16's gas port is located 12.5" forward of the chamber and 7.5" back from the muzzle. The M4/M4A1 Carbine's gas port sits 7.5" in front of the chamber and 8.5" back from the muzzle. The Armalite Mid-Length Carbine places its gas port 9.5" in front of the chamber and 6.5" behind the muzzle. All this serves to put the Armalite Mid-Length Carbine's gas port closer to the full-length AR-15/M16's optimum operating pressure curve allowed by its 20" barrel. This results in less gas port erosion, reduced heat, slower bolt velocity, improved extraction, and a longer sight radius."... In short it has no disadvantages. It's only short coming presently is there are a limited # of barrels choices currently available but the choices are constantly growing |
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I've always thought the midlength was a neat idea but didn't get too excited about it until a friend was buying his first AR and went with an Armalite M15A4. After trying his rifle out and comparing it to my favorite AR, I was really sold on the midlength concept.
In fact, my last barrel with a carbine length gas system is on the EE right now. |
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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. |
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The defensereview.com article quoted above says the gas port is located 7.5" back from the muzzle on the M16 and M4 barrels, but 6.5" behind the muzzle on the midlength. Does this mean the ring on the bayonet guard sits 1" futher forward on the flash surpressor than normal? If so, how secure is it? |
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It's very secure. The A2 flashhider is a strong piece and will stand up to a lot of abuse. Just ask anyone in the Military with an old standard GI sling. When the sling comes undone the weapon falls directly on the flashhider everytime. I've never seen one break yet. You figure you have an extra 1 inch of blade to use as well. |
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+1 TWL saved me a lot of typing... |
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I'm not doubting the accolades of the mid-length but I have failed to experience the problems that it is correcting. Despite this, I have a mid-length project in process
Bomber |
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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. |
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If some of the problems are a slightly harsher felt recoil, and more erosion of gas ports, and slightly more heat, etc - you might not notice them as "problems" per se, but might notice a slight improvement with the middy over the standard carbine/M4. I never had any problems with 16" carbines either, and still have one - but I like my midlength a little better. Looks better too |
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Hey guys,
Thannks for taking the time to re-enforce the benefits. Like I said, I wasn't doubting them and they make perfect intuitive sense despite the fact I am a mechanical engineer. I have to agree that the rifle length FF tube looks great on a carbine length barrel. If it operates better then I'm really all for it. In fact I'm piecing together a midlength gun right now. I'm saving for a 1:7 twist midlength barrel although the twl's post has peaked my interest. I currently have a carbine length heavy profile, 1:8.5 twist barrel on a RR upper and a LaRue rifle length FF tube and low profile gas block. twl....when you can will you provide add'l details? Bomber |
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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 . |
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Here's my guess twl
Your solution is to keep all the carbine parts EXCEPT...a new gas block. The "old" gas blocks have the gas hole drilled at the rear barrel band; yours will be drilled at the front, and perhaps the gas block itself slightly lengthened, and of course the gas hole in the barrel drilled further out. This is such a common sense solution I bet the Armalite guys will be kicking eachother in the pants for not having come up with it themselves. This is a MUCH simpler solution with only one unique part. Am I right? I've been designing guns since I was a teenager... |
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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. |
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I'm sorry but I do not see this concept as a better solution or even as a "just as good" of a solution. Lets look at this point-by-point. The Armalite solution takes 3 special parts, the barrel (because of the gas hole location) the gas tube and the handguards. Seems to me your solution would also take three special parts. Barrel (because of the gas hole location), gas tube (maybe I'm not fully getting it but I don't see how a standard carbine gas tube would work with an FSB that has it's gas hole drilled 2" forward and TWL's post seem to confirm this?) and a new FSB\gas block. Maybe it's just me but I would rather replace a set of handguards then an FSB\gas block? Either way, I don't see any parts advanatge to either design. Besides, what's all this crap about buying special parts for a mid-length? If you are building a new AR, you have to buy a barrel, gas tube and handguards regardless of what configuration you are building. Before you had to buy either "Rifle" length or "Carbine" length gas tube and handguards (depending obviously on setup). Now you have one more choice. What's the big deal? So let's look at the functional advantages. Let's assume that both systems correct the negatives associated with the carbine gas system listed above equally. That being the case, the TWL design stops there. The Armalite design also adds a longer sight radius, handguards that covers more of the barrel and also provide more real estate for accessory mounting and also allows for the use of a standard bayonet. Are these major advantages? Well that's certainly debatable but they are advantages. I respect and admire people like TWL for thinking outside of the box and trying to be innovative but unless I'm seriously missing something, I don't think anybody at Armalite (or anyplace else) is going to be kicking themselves for not thinking of this first. (This also assumes that they in fact did not already think of this (and maybe even tried) it before deciding that moving a standard FSB forward 2" is a better solution?) Mind you, this is just my $.02 on it |
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Not to talk for Chris but I happen to know that is a CavArms C1 (A1 length) stock. |
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cool, thanks, I was thinking about putting an A1 stock on my next (midlength) AR build. |
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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. |
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TWL
Thank for the follow up. I'm sure you've probably already divulged more then you planned to so we'll save this for another day. |
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You're a stand up guy in my book. You handled the hostility with grace and dignity. props Bomber |
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Respect and Admire are not two words that I normally associate with hostility. |
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Whatever dude....I found it to be unecessarily pointed and curt. It could have been a little less sharp. The respect and admire thrown in at the end came across as disingenuous. MHO. Bomber |
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Whatever dude is correct. I am a "Straight-to-the-point" kind of person but my post was not meant to be rude or inflammatory. I try to write exactly what I mean but sometimes my posts are misinterpreted. Regrettable but I've come to realize that this is the Internet and people tend to want to read things "into" what you write. Like you said, whatever |
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Whatever your "whatever" on my "whatever" . I understand about being straight to the point. I have that problem in verbal communications. Typing adds enough delay for me to control it better on the internet. Sorry for mis-interpreting your intentions. I am however, still impressed with how TWL handled your objections...mmm Maybe I should have substituted "objections" for "hostility". mea culpa. Bomber |
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No harm, no foul |
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Hey, evolution designed us to interact face to face with visual cues such as the other person grasping us around the neck when we annoy him.
This internet medium has not benefitted from 10K years of acculturation. We must grow into it...so stop being hostile, rude and inflamatory. |
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Damn, I really like the looks of those Armalite M15 middies......just what I need....another AR!!!!
thanks alot, you bastards!!!!! |
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Desertmoon, what are you saying, dude? You mean you're not getting a brand new RobArms XCR?
John |
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Back to the top so other who missed it...
and I locked the other. |
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More barrels get bent during jumps and boynett training than anything else. Securing further out on a non-solid part of the FS is probably not a good thing.
That said, the usefulness of a bayonett on a carbine is questionable anyway. It's not that much further out than you can reach and you have better control of it when it is in your hand. Chances are the other guy is going to have a longer rifle than you anyway, so if it comes to bayonetts you are already at a major disadvantage. Also, why do you want to add 5" of length for .00001% of situations to what is supposed to be a compact weapon in which the shorter length will benefit you in many more circumstances and take the chance on bending your barrel? If it is a looks thing, I am in your boat though. They do look kickass for when you are taking pics! In that case the mount will be sufficient! |
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cgv69 is heading in the right direction with his thoughts as far as I am concerned. I don't see anyone adopting this new method of turning a carbine barrel into a midlength. Who will this be marketed towards? Someone who can't afford to buy a new midlength barrel assembly but has a few bucks and time to replace their gas tube and front sight base along with DRILLIING a new hole in their carbine barrel?
I don't see people thinking they need to jump on a midlength bandwagon so badly that they feel the need to drill into their barrel. When I decided to go midlength, I decided to get all the goodies and ordered it with an upper from ADCO. I got the ramps, SS, 1:7 twist, yada yada yada. I just sold my carbine barreled uppers and bought one good midlength upper. I'm just not seeing enough interest in midlengths to cause people to want to drill barrels and gas ports. there are plenty of midlength barrels out there and the number is growing. i wish you luck but this is so non-standard it's not gonna fly too far. Imagine someone buying a used "midlength" off of the EE and then removing the FSB to find out the barrel has TWO gas ports. YIKES!! |
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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. |
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Prolly a good thing you did since I just saw this thread. Yes it is an A1. |
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I picked up a used, standard AR carbine (bushy upper/eagle arms lower) from a board member here several months ago. I have had no trouble with it in the 400ish rounds I put down the pipe, so, because I can't leave well enough alone, I'm converting it to a midlength. I'm accomplishing the task by removing the old FSB and gas tube and installing a YHM flip-up FSB, part #9394, and a mid-length gas tube/handguards. The beauty of the 9394 is that because of the way it bolts to the barrel, the slight reduction in diameter ahead of the true FSB location doesn't matter--the 9394 snuggles up to the barrel tightly. I still have to drill the gas port, and I'll use the shaved front ring of my old FSB to cover the old gas port (I'll use a dremel to remove all from the FSB but literally a ring that will encircle the bbl and cover the old gas port, and I'll pin it in place with one of the taper pins I removed).
I did run into one hitch. I learned, after dremeling (of course), that midlength handguards are designed for a triangular handguard cap, not a round one. At worst I've ruined only $15 worth of handguards, but when I get a triangular cap I think the dremeled handguards will still work. Only remaining question I have is what size to drill the mid-length gas port. I read somewhere that a port size of .080 inches ought to do the trick. I figure it ought to be slightly smaller than a rifle port and slightly larger than a carbine port. I need to do some searching to find out what those sizes are and compare to the .080 measurement I have. Comments, questions? I'm I nuts? twl, I'm quite curious to see your mid-length kit. |
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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. |
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twl, do you have exact figures for the port pressure of the mid length gas system? I read an Armalite technical document www.armalite.com/library/techNotes/tnote48.htm that mentions how the M16 gas sytem produces 13,000 psi of gas port pressure while the M4 produces double the amount (26,000 PSI). |
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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 |
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Thanks man! |
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Newbie question concerning the thread topic:
Is a 16" midlength considered a carbine, or is a 16" midlength considered a rifle? (Or is it just a middy?) hinking.gif |
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Its Both!!!! (I am anxiously awaiting the completion of my middy) |
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