hatchetbearer
Member
I never understood why the groove in the middle of the barrel between the FSB and the muzzle is there. Can anyone clairify? seems like a waste of machining to me.
M4 Barrel Profile
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Bartholomew Roberts
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It is there for the military because the older M203 grenade launchers needed that groove to mount (since they were designed for the original lightweight 20" barrel profile).
It's a excellent example of how the military has to accept compromise in mechanical design to accommodate different uses on the battlefield. Institutional thinking causes it. IIRC, the newer M4s now delete the cuts. They cause barrel overheating and a weak spot (duh.)
Think about that - it took over a decade to realize the M4 carbine length platform isn't the best application for a 40mm grenade launcher. It just needs to be on the M16A4, it's better off mounted on that.
Looking at other parts of the platform, like adjustable stock and quad rail, you begin to see the same concept - an institution's attempt to merge two competing users demands in the same design.
Just because it's military doesn't mean it's the best idea out there.
Think about that - it took over a decade to realize the M4 carbine length platform isn't the best application for a 40mm grenade launcher. It just needs to be on the M16A4, it's better off mounted on that.
Looking at other parts of the platform, like adjustable stock and quad rail, you begin to see the same concept - an institution's attempt to merge two competing users demands in the same design.
Just because it's military doesn't mean it's the best idea out there.
Jeremy2171
Member
AFAIK the "M4 barrel cut" is still current production as the cut is required for the front mounting point of the M203.
The M4A1 has the same cut but a heavier barrel under the handguards to help with the overheating since the M4A1 is a full auto weapon.
The M4A1 has the same cut but a heavier barrel under the handguards to help with the overheating since the M4A1 is a full auto weapon.
migkillertwo
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its to mount an m203 grenade launcher.
Z-Michigan
Member
Point to ponder: assuming that the M4 cut makes sense on military M4s which might actually carry an M203, just how much sense does it make on civilian M4geries? Am I really supposed to believe that someone who can afford a NFA-registered M203 is going to stick with a $900 semiauto M4gery? Just how many people really want those 37mm flare launchers that look like the M203?
Just another argument for a midlength barrel on a civilian 16" AR.
Just another argument for a midlength barrel on a civilian 16" AR.
Hammerhead6814
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Why do people want M4 profile barrels then? Civilians I mean? Just historical accuracy or fun?
sv51macross
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Well Z, most people get it for the looks, some think it looks cool. Simple as that. Also, a M203 is $1500-$2000 + NFA tax, whereas to make a full-auto M4rgery would require a $10,000-$20,000 M-16. So, there is a rather substantial price gap between a M203 and FA M4gery.
And not just M203, the Masterkey is also designed to fit the M4 barrel...
And not just M203, the Masterkey is also designed to fit the M4 barrel...
hatchetbearer
Member
Didn't the Masterkey idea get kanked because it puts undue stress on the front pin that holds the upper and lower together? Granted a 12ga/5.56 home defense range toy is a fun idea, but not for my personally owned weapons if its going to break them.
sv51macross
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^ Yeah...
I wonder, in similar way to how buffers are made for AKs, if one could fashion a stiff rubber/polyurethane 'plug' that screwed to the back of the Masterkey receiver and braced the shotgun against the magwell and actually put negative pressure on the retaining pins.
But that's o/t.
Question, both the M16A4 and M4A1 these days come standard from Colt with the KAC rails installed, correct? I've seen M203s with the rail mounts, is that going to become standardized? If so, would the military at some point move to HBARs or med-cons?
I wonder, in similar way to how buffers are made for AKs, if one could fashion a stiff rubber/polyurethane 'plug' that screwed to the back of the Masterkey receiver and braced the shotgun against the magwell and actually put negative pressure on the retaining pins.
But that's o/t.
Question, both the M16A4 and M4A1 these days come standard from Colt with the KAC rails installed, correct? I've seen M203s with the rail mounts, is that going to become standardized? If so, would the military at some point move to HBARs or med-cons?
Jeremy2171
Member
You don't have to have the NFA tax to own an M203....as long as you don't have the 40mm barrel its a title one weapon (i.e. rifle) here is mine....
You can add an M203 barrel but in 37mm without paperwork or I'm having a demil barrel sleeved to shoot 26.5mm flares until I move and decide to get my DD tax and make it 40mm. Then its time to shoot the $7 "orange death" rounds!
You can add an M203 barrel but in 37mm without paperwork or I'm having a demil barrel sleeved to shoot 26.5mm flares until I move and decide to get my DD tax and make it 40mm. Then its time to shoot the $7 "orange death" rounds!
Jeremy2171
Member
Yes but you must remove the bottom KAC handguard then mount the M203 directly to the barrel just like on an M16A1/A2/M4.
MachIVshooter
Member
Case in point, nearly every military small arm the US has used was designed by private companies or individuals, whether commissioned or simply plucked out of the civilian market.
Same goes for the pioneering of every other aspect of our military arsenal. The military didn't really start doing anything on its own. However, they DO and HAVE funded - with a desired outcome in mind - probably almost every advancement afterward.
MachIVshooter
Member
Very true.
Bartholomew Roberts
Member
The M4 used to be popular for civilians because even not that long ago, your choices were M4 or HBAR and the M4 is over half a pound lighter. Now, not so practical given some of the other choices; but still popular.
The M4 weighs 6.22lbs, the Hbar weighs 7.28 lbs, thats over a pound heavier, quite a difference.
The M4 version also offers other features standard that some manufacturers dont put on all carbines. So if you want to guarantee those features you need to get the M4 carbine, or pay more to have them added.
Unless you want a flare or greande launcher, the barrel cut is just for appearances.
The M4 version also offers other features standard that some manufacturers dont put on all carbines. So if you want to guarantee those features you need to get the M4 carbine, or pay more to have them added.
Unless you want a flare or greande launcher, the barrel cut is just for appearances.
Bartholomew Roberts
Member
If you compare the unloaded Bushmaster M4A2 14.5" to the loaded Bushmaster 16" HBAR, then those figures are correct. However, I was talking about just the barrel profile.
Just the M4 barrel would be about 2.1lbs and the 16" HBAR would be about 2.7lbs - so about 0.6lbs of the weight difference in those two rifles comes from the barrel (and sitting in front of the barrel nut, it has an even more noticeable effect on balance). This was one reason the M4 profile got popular.
FlyinBryan
Member
i prefer the 16" hbar.
i had a chance to handle both, the m4 profile, and the hbar, and it wasnt enough difference for me to really be able to tell.
i tote it around sometimes, but i mostly shoot from a bipod, and the slight accuracy edge is worth the extra 6-8 ounces. (to me)
(i had a 20" hbar, and its a much more noticable difference over the 20" gov. profile)
i had a chance to handle both, the m4 profile, and the hbar, and it wasnt enough difference for me to really be able to tell.
i tote it around sometimes, but i mostly shoot from a bipod, and the slight accuracy edge is worth the extra 6-8 ounces. (to me)
(i had a 20" hbar, and its a much more noticable difference over the 20" gov. profile)
i've never had a use for that cut. never even liked the looks of it. the only guns i own with it are because you can't get colt 6920s without it. i strongly prefer the lighter barrels Bart mentioned.
given that colt had to change the barrel on the civilian/leo gun (16" instead of 14.5) we could speculate why they chose to keep that cut. one can easily imagine the reaction of gun nuts if colt refused to offer that feature on the civilian models, despite its uselessness. or maybe they thought LEO had a legit use for it for launching tear gas or something. who knows?
given that colt had to change the barrel on the civilian/leo gun (16" instead of 14.5) we could speculate why they chose to keep that cut. one can easily imagine the reaction of gun nuts if colt refused to offer that feature on the civilian models, despite its uselessness. or maybe they thought LEO had a legit use for it for launching tear gas or something. who knows?
boricua9mm
Member
The M4 used to be popular for civilians because even not that long ago, your choices were M4 or HBAR and the M4 is over half a pound lighter. Now, not so practical given some of the other choices; but still popular.
That's exactly it! I can remember those days. If you wanted a 16" barrel, you either got the HBAR, the M4 profile, or the lightweight pencil barrel. Back then, the M4 profile was "splitting the difference." I also agree that in today's market, they might not make the most sense due to other options being available. I still think they look nice and mine still shoots great.
I once had a conversation at a range with some young buck who was questioning my M4 profiled barrel. He spouted off jargon about overheating, unbalanced feel, unnecessary, etc. I told him he must be new to the AR15, or he'd remember the days (10 years ago) when you didn't have the plethora of barrel choices that you have today. Of course, that ended the conversation and he sauntered off.
I don't understand why people get so up in arms about M4 profile barrels. There was a time when "M4Gery" was the biggest fad, then "SPRs" came out, then "Recce", etc. What's next, poking fun at SPRs?
That's exactly it! I can remember those days. If you wanted a 16" barrel, you either got the HBAR, the M4 profile, or the lightweight pencil barrel. Back then, the M4 profile was "splitting the difference." I also agree that in today's market, they might not make the most sense due to other options being available. I still think they look nice and mine still shoots great.
I once had a conversation at a range with some young buck who was questioning my M4 profiled barrel. He spouted off jargon about overheating, unbalanced feel, unnecessary, etc. I told him he must be new to the AR15, or he'd remember the days (10 years ago) when you didn't have the plethora of barrel choices that you have today. Of course, that ended the conversation and he sauntered off.
I don't understand why people get so up in arms about M4 profile barrels. There was a time when "M4Gery" was the biggest fad, then "SPRs" came out, then "Recce", etc. What's next, poking fun at SPRs?
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