Anyone know if the Smith & Wesson Bayonet [SW3B M9] will mount direct to the M&P15 Sport?

The link below states that a bayonet adapter is needed for a carbine length bbl.

If so, are there other Bayonets that mount direct without the need for this costly adapter [looks like a gunsmith is needed to install it]?

It looks cool on the AR.


S&W SW3B M9 Bayonet.JPG

You gonna be cutting some wire and sneaking up on them? Or you planning a little trench warfare with the neighbors?

You need the carbine adapter if you have a 16 inch carbine barrel no matter which mil spec version bayonet you buy. There are some commercial models around of the older bayonets that are touted for carbines as mil spec but they are actually commercial versions that have an increased handle length. The actual military original version designed for the carbine is a rare find now a days, and the M9 mil spec varient/version has become the standard.

That bayonet lug on the Sport is intended for accessories such as a bipod.

Modern bayonets are made for the M16 20 inch barrels, and M4 14.5 inch barrels, they both have a distance from bayo lug to flash suppressor of right around 4.75 inches.
Commercial barrels by law must be 16 inches, so they're about another 1.5 inches longer, which means they will wobble.
Ummm, YES IT WILL.
What do they think is on every real M4 out there?

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Hold my beer and watch this!

Or....just make your own. I put this one on an old Savage some 35 years ago. It hasn't fallen off yet. The bayonet lug started out life on an old German Masuer. It was either WWI or WWII vintage....been too long to remember.

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Stu

The standard issue U.S Military M-4 Carbine has a 14.5 inch barrel. The mil spec U.S. military M9 bayonet will fit the standard issue U.S Military M-4 Carbine.

The civilian mil-spec versions of the M-4 are essentially identical to a military M-4 but with a 16" barrel and of course changes to exclude the auto or burst fire modes and to meet compliancy laws where sold.

The differences between the military and civilian M-4 for fitting a bayonet is shown in the picture below, although they are different models (the top is the newer M9, the bottom is the older M7) of the bayonet it serves to show the difference in fit for where it should be vs where it should not be;


In the top pic on the standard military M-4 carbine you can see where the bayonet barrel ring would need to fit which is directly behind the flash supressor. In the bottom pic on a 16 inch barrel civilian version M-4 carbine you can see where the bayonet does not need to fit. The word "fit" used here is relative because the technically correct fit position is in the top pic and the bottom pic is technically not the correct fit position because the barrel is a 16 inch barrel so the bayonet barrel ring sets further back from the flash supressor. So, if we use "fit" as a subjective word here, all that really remains is to accommodate the mil spec bayonet barrel ring if your just going for looks or basic function, and don't care about where the bayonet ring is really supposed to go.

The purpose of the tacticool22 adapter is to bring the diameter of the flash supressor further back down the barrel. The real correct position for the bayonet ring is on the flash supressor, just in front of the washer so the bayonet ring is the diameter of the flash supressor to fit on it. If the barrel diameter is less than the flash supressor diameter at the point on the flash supressor where the ring is supposed to really go then you need the adapter.

If you have the standard 16 inch carbine barrel you can get the S&W SW3B M9, then get the Tacticool22 Bayonet Barrel Adapter for M7 M9 M10 and M11 Bayonets there is no gunsmiting required. The tacticool22 adapter is a slip over thing you can put on yourself, it slips over the barrel and accommodates the mil spec bayonet barrel ring (like the S&W SW3B M9 you picture.) so it does not rattle around which is something you certainly do not want as it damage the barrel. The tacticool22 page has this for installation:

"Easy to put on. Remove your flash hider and crush washer. Slip on the adapter, new crush washer and screw on your (new?) flash hider or other muzzle device til it is timed the way you want."

If the Sport has the thicker barrel profile already though you may not need the adapter, or the adapter may not work on it. The adapter. from the pictures on the tacticool22 web site, seems intended for the standard carbine barrel profile, so you may want to gice them a call and ask to make sure it will fit before you buy it.

The tacticool22 adapter does nothing to fit the bayonet ring in the technically correct spot (immediately behind the flash supressor), it does serve the purpose by allowing a mil spec bayonet to be fitted to the 16 inch carbine barrel without it rattling around and in doing so does satisfy the look, feel, and "use" aspect even though a few more inches of blade length is lost due to sitting further back (which is one reason why the standard military fit is with the bayonet ring fit at the flash supressor to get every inch of blade possible yet still mount the bayonet on the weapon).

So (if needed) all you need is the adapter, $16.50 and you put it on your self (easy to do), and the S&W SW3B M9 bayonet.

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I'll stick to the standard AR bayonet. I'm not buying special adaptors.

Then don't?

We are talking about a sport right?...doesn't it have a heavier barrel profile than the rifles in the pictures. I haven't driven to my Dads to look but I know my rifles barrel is heavier than his H-Bar especially without the milled out section for the grenade launcher.

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Grover Oathkeeper

Well, the poster said:

"The link below states that a bayonet adapter is needed for a carbine length bbl."

So if the sport has a carbine length barrel, but its already the proper size then he may not need the adapter. However, the pic he showed with the S&W bayonet (on the bushmaster M4A3 barrel) has the standard carbine barrel profile and the standard carbine barrel profile already has the thicker barrel profile area where the bayonet ring would go on a 16 inch barrel. I had the impression this area is the same size as the Sports overall barrel diameter. Yet, the adapter was still needed on the bushmaster with the same area barrel diameter where the bayonet ring is located in the picture as the Sport (I think).

Is the Sport barrel larger in diameter than the larger diameter of the standard carbine barrel at the location where the bayonet ring would be located on the 16 inch barrel?

The thicker portion of the standard 16 inch carbine barrel where the bayonet ring would sit is 0.75 inches on the S&W M&P 15 series with standard carbine barrels. What is the barrel on the Sport?

First I need to correct my original post.
The attached photo states you need the adapter if you have the carbine length foregrip [not bbl as I stated].

Looking at the photo, I can see the pictured barrel is not the same as my sport. I do not know the dimensions of either barrel?

What seemed odd to me was that S&W incorporated the Bayonet / Bipod mount and also makes their own Bayonets.

So the need for an adapted appears to be a design flaw?
Why make the Bayonet if it does not fit your firearms?
Unless this Bayonet is made for models S&W does not manufacture [M4]?

I have an M4 Bayonet that was my Dad's from the Korean war & mounted on an M1 I believe?
The Bayonet is marked "M4" while the sheath is marked "M8".

Anyway, I broke it out just to see if that really was a Bayonet mount on the sport, and it is. The size does not match but it definitly is similar.

Foxtrot this is a great quote:
"You gonna be cutting some wire and sneaking up on them? Or you planning a little trench warfare with the neighbors"?

I have no such plans, just was going to purchase a survival knife and thought being able to combine the 2 would be a conveinence. Plus, if and when I run out of ammo, I'm not left with a 7 pound club!

Yes, it says carbine length foregrip because the carbine length foregrip also means the bayonet lug is further back from the flash supressor on a 16 inch barrel. Due to the bayonet handle length this shifts the bayonet barrel ring back as well, so the area on the barrel where the bayonet ring rests needs to meet what the ring was designed for.

No, the need for an adapter on the standard 16 inch carbine barrel is not a design flaw, its a result of having a 16 inch barrel with a carbine length foregrip instead of the standard military carbine 14.5 barrel with a carbine length foregrip.

S&W makes both the rifle and the bayonet; They make the bayonet to adhere to mil specs, and the mil specs for a military version carbine is the 14.5 inch barrel, where the rifles they sell to the civilian market are required to have a 16 inch barrel. Although you can purchase the S&W bayonet, its clearly a product aimed at military applications else it would not have a bayonet lug and be formed as a bayonet, it doesn't even appear on the S&W web site in the knives section. Its made to fit military rifles with the mil spec dimensions needed for military rifles and civilian carbine rifle owners with 16 inch barrels need adapters. Why spend the manufacturing cost to re-manufacture the bayonet just for the civilian carbine rifles when the focus of the product is aimed at a military application market and the civilian market can get a $16.00 adapter for the standard carbine 16 inch barrel and the vast majority of gun owners do not have a need for or want a bayonet?

The bayonet does fit the M&P 15, latches on to the bayonet lug. The issue in question is the barrel area where the bayonet ring sits. If its the standard 16 inch carbine barrel profile with carbine length foregrip the adaper is needed. So we are trying to determine if the Sport barrel (since its not the standard 16 inch carbine barrel profile) also needs the adapter, if it does not then fix bayonet right now.

Another question. Doesn't the Sport come plain barrel with out a flsh "hider" ? So,wouldn't you "might" be able to find a "better" flash hider that's longer,thinker, to help with the loose fit ?

I think the Sport comes in three flavors, two with flash supressor, and one without. Not sure which version he has.

The flash supressor doesn't matter in this case anyway as the bayonet ring would be too far away from it.

If he has the model without the flash supressor with the plain barrel then the use of the tacticool22 adapter is out of the question if an adapter is needed because there would be no way to attach the adapter because the flash supressor holds it in place.

S&W actually has two different types:

Smith & Wesson Special Ops SW3G Bowie Knife

and...

Smith & Wesson Special Ops Bayonet Knife Black Spear Point

I wonder if S&W produces these now themselves or still imports them from Taiwan like they did originally?

***************

Really the fore grip (I guess they mean handguard) has nothing to do with the bayonet, gas block/front sight, or anything else.
There are 3 standard lengths for the fore end, Carbine, Mid length, and full, none of which affect the distance between the bayo lug and flash hider.
All true Mil Spec rifles are about 4.7 inches from lug to hider, including the 20" barreled A2s.
The difference is only in the commercial 16" barrels vs the Military 14.5 inch barrels.

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Hold my beer and watch this!

With the handguard being at mil spec carbine length then the barrel being 16 inches it means the lug is set back from the flash supressor a further distance by the additional length of the barrel. Thats what I meant when I posted what you quoted.

How it should have read is; Yes, it says carbine length foregrip because the carbine length foregrip also means the bayonet lug is further back from the flash supressor on a 16 inch barrel.

Sometimes I post something and it doesn't sound right because any corrections I made while typing don't show up because for some reason the forum and my browser don't seem to get along too well at times. So I make edits and only some of them show up or none at all and I don't go back to look. Sometimes I have to make the same edit several times to get it to stick even though it was correct when I hit the 'Save' button. Sometimes it will take the edit and then wipe out part of another line and join things together in weird ways. Went back and corrected the post.

Not mine, but here is a pic I found that shows one persons solution with a sight mounted on the barrel of an AR where the sight has a bayonet lug. They do, or did at one time, make just bayonet lugs that clamp on the barrel and you could try one of those then space it properly for the bayonet ring to fit properly on the flash supressor.



I don't think thats the S&W SW3B M9 bayonet, but its a reasonable copy to get an idea of what it would look like mounted with a lug on the barrel.

DPMS used to sell a clamp on lug that would work fine if you don't mind clamping something on the barrel, but they discontinued them. There is someone out there who sells one that would work, I come across something every once and a great while when searching for something else but finding it is like looking for a needle in a haystack.

However, I did find a clamp on lug for the standard weight barrel, $24.95 and says its in stock, here > AR-15 Bayonet Lug Adapter, Standard Barrel < I think this will work on the Sport barrel too but you will need to check it out to make sure. I can't vouch for the quality and suitability of that clamp on because i've never used it, so you will need to decide for yourself.

You may be able to find a clamp on lug at a gun show too, there is always a private person someone with a table set up selling something at a gun show that has a few of those hard-to-find items or those things no one else buys much of. Also check out the local gun shops, and pawn shops that sell guns too. Just for giggles I went to my LGS yesterday, its about a mile from where I live, because I knew they carried the S&W SW3B M9 bayonet and I wanted to take a look at it up close. They would throw in a clamp on lug with the S&W SW3B M9 if you bought one, of course their prices were a little higher than what you can find on line. They did not have a Sport in stock or I would have taken a look at that too for you in combination with the S&W SW3B M9. You could also find another clamp on thing (like a sight), maybe a used but in good shape thing, that you can modify by removing the sight or whatever else is on there, just leaving the clamp on lug as long as you don't need to compromise the integrity of the clamp portion. I've seen a few sales on bipods that included a clamp on lug too, and there is a chance in a LGS or at a gun show or even on line that you can get a clamp on lug from their "gun smith" person or services if they offer to mount things for people who purchase weapons when they may not directly advertise a clamp on mount for sale. You may be able to find a private individual on line that is selling some of their stuff to get some extra cash and one of their items may be a clamp on lug that will work.

If you use the clamp on bayonet lug you do not need the adapter because then you move the clamp on further up to account for the 16 inch barrel length so the bayonet ring is in its proper postion on the flash supressor (if you have a flash supressor - if you don't then you are out of luck)

Personally, I would not clamp a seperate lug on my barrel and would go for the tacticool solution first if I really wanted to mount a bayonet and could live with the thing not in the technically correct position and can live with the shortened blade projection. Of course i'm more into the practical real world use rather than the cool factor look.

Taking into account the S&W SW3B M9 bayonet dimensions - If you have a 16 inch barrel and a carbine handguard; The overall length of the bayonet is 12.75 inches, the blade is 6.5 inches, this means a handle length of 6.22 inches. Taking into account the measurement from the bayonet lug on the Sport at the front sight to the end of the flash supressor (if you have one) its approximately around 7 to 8 inches (not exactly sure for the Sport), this leaves a blade length beyond the end of the barrel of maybe 3 to 4 inches.

The last real U.S. military bayonet charge was in Korea, but I believe there was some U.S. military bayonet use in Iraq. Not sure of the exact details but a squad of British soldiers did a short bayonet charge in southern Iraq, killed 3 to 1 and took prisoners too and the rest of the Iraqi forces ran off. I do know though that the British military even today will bayonet the bad guys butt in a heart beat.

Sounds like me, I'm glad this thing only shows that I edited a post, and not the number of times I did!

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Hold my beer and watch this!

when I was in the corps my one order I never wanted to hear was "affix bayonets" LOL I always prayed Spookie would show up!!!

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Grover Oathkeeper