I have been looking for a pic of a pre-ban Midlength Upper with a M9 Bayonet for a long time as from my measurements it always seemed to me like Armalite had got it wrong when the set the length of the mid-length grip and where they chose to mount the gas block...

Well, I was correct...  Here is a link with the side by side pics...

www.quarterbore.net/forums/showthread.php?p=1063

Now, it would work...  just seems sad to me that they designed it that way!

Ooops... Didn't realize Chris posted his pics here too:

ar15.com/forums/topic.html?b=3&f=118&t=234265

I will leave the post however as I have seen it asked WAY TOO MANY TIMES if a midlength will corectly mount a Bayonet...

Ken,

No problem, Glad I could help. I know this question comes up on a regular basis. Sorry my pictures couldn't be better. My camara and lack of photography skills makes for a bad combo! :-)

I agree with you in the sence that I wish Armalite and RRA had placed the gas port in the same relative position to the end of the barrel as is done on 20" and 14.5" barrels but I wonder if there is a reason for it? Just guessing out loud but maybe that extra 1" makes a difference in some other way that we are not aware of? Maybe that just wanted to make the gas tube\sight radius as long as possible while retaining the ability to use a bayonet which brings up my other point...

IMO, a bayonet is just as useful in this configuration as it is on a normal 20" rifle or 14.5" M4 meaning that the bayonet did not need to be modified, locks on just as tight (or loose as it were) and does not block the FH or cause any other negatives that I can see or think of?

I am pretty confident that this was either a huge screw-up OR Armalite did this so that is some idiot went out and used a bayonet to commit murder that Armaite would be able to say... "It wasn't designed to be used with a bayonet!"

Armalite is a stand up company so I have a feeling it was just a screw-up...

That difference in less then an inch would not impact the function of the weapon at all...  In fact, I would rather see Armalite or RRA make the barrel just a little longer (16.6-inches or so) such that the bayonet would mount corectly...

Also, it is funny how Knights Armament Medium Short FF RAS Tube is the correct length so that if the gas block was mounted just forward of the FF RAS that the bayonet would mount in the right location...  Following is some details on why I say that and how I still plan to build a 300 Whisper Upper if I ever stop spending all my money on other projects:

quarterbore.com/300whisper/300upper.html

I have wondered for a LONG TIME if KAC was going to make some mid-length carbines to the CORRECT size but I have yet to see one where they did it!

Ken

This may be a dumb question - but why is the Armalite/RRA moutning so problematic?

Is it because if enough force/torque were put on the bayonet, it could somehow twist the FH - because the bayo ring is does not overlap the barrel itself any longer?

Like I said, it's probably just a dumb question  - but I really don't understand why the first pic is so much better than the second pic.


Or is it purely a matter of it being "correct" in the historical and traditional sense?

Quoted: Or is it purely a matter of it being "correct" in the historical and traditional sense?

This is the Main Reason!

A flash hider is some darned tough steel so you would not be likely to damage the gun or bayonet any worse with either set-up...  

I guess it's like the Purple Bushmasters... they work too, right?

Quoted: Quoted: Or is it purely a matter of it being "correct" in the historical and traditional sense? This is the Main Reason! A flash hider is some darned tough steel so you would not be likely to damage the gun or bayonet any worse with either set-up...   I'm guess it's like the Purple Bushmasters... they work too, right?

I not one to tell people what they should or shouldn't care about - I was just curious if there was some mechanical or physical reason it was bad, or if it was an appearance thing.  (you had me worried there)

I personally don't care about the appearance thing, since the midlength is not an "original" look anyway, so as long as the bayonet attachment works, I'm happy.   Plus, now I can stay an extra 1/2 inch further back from zombies, aliens, foreign invaders, etc. - that's got be a good thing!  



Seriously - thanks for the clarification.  I appreciate it.

The Knight's SR-25 Carbine was the first production mid length gas tube rifle I can remember.  Had always thought that the ArmaLite mid length gas tube was a copy of the Knight's, but the gas tube lengths are different?

Instead of a "screwup," has it been considered that since 16" is the minimal legal overall barrel length which isn't subject to NFA, that Armalite just said "make them 16 inches" and called it a day?  After all, until the ban and after the ban, no one was really fixing bayonets, right?  I would doubt the ability to mount a bayonet ever entered their line of thinking.

It's kinda like having bayonet lugs on a 16" M4 barrel.  The military doesn't use 16" barreled M4s, but the after ban barrels have them.  Why?  You have to buy a special bayonet just to fit it.

As always, YMMV.

Just because the military hasn't used them doesn't mean that a 16-in Midlength wouldn't be logical at some point for the same reasons we like them...  More real estate to add attachments, better grip positions, better sight radius, better velocity (then 14.5-in), abuility to add a pig stabber.

I am not badgering the Mid-length as a bad idea... simply expressing that I find it foolish that they made it this way...

Now, in regards to the KAC Mid-Lengths...  I would love to get some more info on these...  I thought the difference in the gas tubes with the SR-25 as opposed to the AR-10 had to so with the upper receiver...  Is there also a difference in the SR-15 vs AR-15 Midlength uppers and their gas tubes?

Would a Phantom flash suppressor remedy the issue somewhat?  I know that it is longer than an A2, but is the back part of a Phantom longer than the A2 behind the vents?

Quoted: Now, in regards to the KAC Mid-Lengths...  I would love to get some more info on these...  I thought the difference in the gas tubes with the SR-25 as opposed to the AR-10 had to so with the upper receiver...  Is there also a difference in the SR-15 vs AR-15 Midlength uppers and their gas tubes?

Parts compatibility with the AR-15 was a top priority with the SR-25.  The full size SR-25 uses a standard AR-15 gas tube.  The AR-10 uses a longer proprietary gas tube.  

I don't know if the SR-25 Carbine, and the SR-15 mid length gas tube, and the ArmaLite/RRA middy tubes are the same thing.  Had always thought they were, till today.  Never missed with any of those parts myself.

Quoted: Instead of a "screwup," has it been considered that since 16" is the minimal legal overall barrel length which isn't subject to NFA, that Armalite just said "make them 16 inches" and called it a day?  After all, until the ban and after the ban, no one was really fixing bayonets, right?  I would doubt the ability to mount a bayonet ever entered their line of thinking.

I don't think QB means screwup in the sense that there is something wrong with it. More in the sense that it would have been nice if it "matched" the 14.5" and 20" barrels as far as location of the FSB to the end of the barrel.

I doesn't really bother me but I do agree with him.

I would like to know how the Armalite\RRA gas tube compares to the KAC? If the KAC mounts a bayo "correctly" then I would have to think either their gas block\FSB is mounted closer to the receiver meaning the gas tube is shorter or their barrels are slightly over 16"?

On the plus side, this does give a little more exposed blade, right?  Let's the blade go a little deeper before being stopped by the hider?

The bayonet will also fit the 11.5" barrell with the 5.5" flash supressor as well.  Why do it?  I don't know, but it works.  I'll post a pic of it...

Quoted: The bayonet will also fit the 11.5" barrell with the 5.5" flash supressor as well.  Why do it?  I don't know, but it works.  I'll post a pic of it...

Yea, I had one of these setups years past and you are correct, they do mount up fine as long as your FH is the correct diameter.  There used to be quite a few FHs that were too large in diameter however...  Or at least I had a couple of them in the past that didn't work with a bayonet.

[Thread Hijack] looking at the bayo lug on my beaner I see that the grooves for the bayo clip are not equal.  It is exactly 3mm. on one side and 1mm. on the other...WTH?[/TH]

how about some complete rifle photos as well