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4/5/2026 9:33:44 PM EDT
I've always wanted to be able to mount an M7 bayonet on my Colt 6721 (AR15A3). It came with a 16" barrel plus the flash hider. I sent it to ADCO and had the barrel chopped so it was 16" with the original FH permanently installed. Still, it wasn't enough for the bayonet to be worth using. Years went by, and along the way I bought an aftermarket M7 but never did anything with it. Then one day recently I said I'm going to buy a bayonet lug extender, and I did. I installed it yesterday and it came out perfect - the upper ring on the bayonet is almost to the end of the FH, providing the maximum usable blade length.




I used an APG extender and its a very impressive little device - it fits great, very straight and very secure when tightened. Why did I want it and how will I use it? I just wanted a way to get the most blade out in front of the rifle. I most likely will never mount that bayonet in anger, but I have it if I need it.
4/6/2026 5:47:37 AM EDT
[#1]
nice

https://thenewrifleman.com/your-rifle-needs-a-bayonet/


Don't be so open-minded that your brains fall out.

General education should not be mere job training, but training in how to be fully human.
4/21/2026 7:26:27 PM EDT
[#2]
So,which is the correct bayonet to use for the M4 carbine that is a direct fit?
4/24/2026 12:06:10 AM EDT
[#3]
This is a 14.5" vs 16" barrel issue

Any M16 bayonet fits an M4 with 14.5" barrel
4/24/2026 2:07:04 AM EDT
[#4]
Quote History
Originally Posted By ROMAD-556:
This is a 14.5" vs 16" barrel issue

Any M16 bayonet fits an M4 with 14.5" barrel
View Quote


Ayup!



Also R653P clones



What worked for a buddy was a sleeve that went behind the flash-hider over the barrel:

Vintage Ain't Retro.
4/24/2026 3:44:05 AM EDT
[Last Edit: Bigger_Hammer][Edited] [#5]
If you are going to shoot a 16" barrel, a mid-length gas system works perfectly with a US issue M-7, M-9 or similar bayonet.

But as pointed out in previous posts, if using the 'carbine' length gas system, using either (A) 14.5" barrel (issued M-4 length) with a pin & welded extended flash hider to = 16" or (B) a bayonet lug "extender" on a regular 16" carbine gas barrel works to put "Mr. Stabby" out front where he belongs.

I so wish we could ditch those idiotic 1930's  'less than 16" barrel = NFA' laws.

Bigger_Hammer
LIFE'S JOURNEY IS NOT TO ARRIVE AT THE GRAVE SAFELY IN A WELL PRESERVED BODY,
BUT RATHER TO SKID IN SIDEWAYS, TOTALLY WORN OUT SHOUTING "HOLY $H!T...WHAT A RIDE"!!
5/18/2026 7:52:58 PM EDT
[#6]
Does anyone know if those knockoff AR bayos from BudK fit the standard AR bayo lug?
I have one M9 copy,and one standard AR bayo copy and neither lock on to my PSA M4 bayo lug.
Or,is it what the article states that I don't have a mil-spec lug on both my PSA M4's?
5/18/2026 11:20:20 PM EDT
[#7]
Quote History
Originally Posted By cwalkin:
Does anyone know if those knockoff AR bayos from BudK fit the standard AR bayo lug?
I have one M9 copy,and one standard AR bayo copy and neither lock on to my PSA M4 bayo lug.
Or,is it what the article states that I don't have a mil-spec lug on both my PSA M4's?
View Quote


The middy barrel I got from PSA accepts bayonets.



My buddy's as well.



Did they change FSB suppliers?
Vintage Ain't Retro.
5/18/2026 11:31:11 PM EDT
[#8]
Quote History
Originally Posted By Z09SS:
The middy barrel I got from PSA accepts bayonets.

https://live.staticflickr.com/65535/51363747333_dd07f69ec7_b.jpg

My buddy's as well.

https://live.staticflickr.com/65535/50521363457_9fc00c22bc_b.jpg

Did they change FSB suppliers?
View Quote

Is that Magpul foliage green?
5/19/2026 8:32:35 AM EDT
[#9]
Quote History
Originally Posted By cwalkin: So,which is the correct bayonet to use for the M4 carbine that is a direct fit?
View Quote


M7, M9, OKC.
I sell firearms produced by the finest child labor in the world, be it Filipino, Muslim, Mormon, Arizonan, or Texan.
5/19/2026 8:36:50 AM EDT
[#10]
14.5” works
16” middy also



Attached File
5/19/2026 10:39:35 AM EDT
[#11]
Quote History
Originally Posted By MudEagle:

Is that Magpul foliage green?
View Quote View All Quotes
View All Quotes
Quote History
Originally Posted By MudEagle:
Originally Posted By Z09SS:
The middy barrel I got from PSA accepts bayonets.

https://live.staticflickr.com/65535/51363747333_dd07f69ec7_b.jpg

My buddy's as well.

https://live.staticflickr.com/65535/50521363457_9fc00c22bc_b.jpg

Did they change FSB suppliers?

Is that Magpul foliage green?


It is!  He fell in love with the color just as they discontinued it and finding the middy handguard turned into a quest.
Vintage Ain't Retro.
5/19/2026 11:01:53 AM EDT
[#12]
Quote History
Originally Posted By Z09SS:


The middy barrel I got from PSA accepts bayonets.

https://live.staticflickr.com/65535/51363747333_dd07f69ec7_b.jpg

My buddy's as well.

https://live.staticflickr.com/65535/50521363457_9fc00c22bc_b.jpg

Did they change FSB suppliers?
View Quote


We've had 2 PSA barrels w/ FSB here, they both mount bayonets just fine.

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