What are the differences between the Military M4 and M4A1's?

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[ARCHIVED THREAD] - What are the differences between the Military M4 and M4A1's?

Posted: 9/12/2005 8:56:24 AM EDT

I know the M4 has 3rd burst and the M4A1 has FA. Are there any other differences?
Thanks in advance.

Posted: 9/12/2005 10:01:27 AM EDT

[#1]

Quoted:
I know the M4 has 3rd burst and the M4A1 has FA. Are there any other differences?
Thanks in advance.

M4 is the RO920 safe-semi-burst

M4A1 is the RO921 safe-semi-full

The first early M4s have a fixed carry handle.

Posted: 9/12/2005 10:07:15 AM EDT

[#2]

I thought the M4A1 was the model # 927...wich model is the 927

Posted: 9/12/2005 11:17:50 AM EDT

[#3]

Anyone else got anything else to add?

Posted: 9/12/2005 11:23:59 AM EDT

[#4]

The M4A1 by spec has a 4 oz heavier barrel and a slightly lighter maximum allowable trigger pull.

Posted: 9/12/2005 12:28:45 PM EDT

[#5]

Quoted:
The M4A1 by spec has a 4 oz heavier barrel and a slightly lighter maximum allowable trigger pull.

No, the M4A1 and M4 use the same barrel.

The RO921HB uses the midweight barrel.

Posted: 9/12/2005 12:41:18 PM EDT

[#6]

Quoted:
I thought the M4A1 was the model # 927...wich model is the 927

There are several Colt products that are rollmarked M4

However the two I listed are the only two that are offically known as M4 and M4A1 and have US Property marks on them.

For example,

The MT6400, RO977, LE6920, etc. are all rollmarked M4 in some way, but they are not USGI weapons.

The RO977 and RO979 are equivalent to the RO920 and RO921 except they do not have US property marks.

Posted: 9/12/2005 2:28:22 PM EDT

[#7]

Quoted:
Quoted:
The M4A1 by spec has a 4 oz heavier barrel and a slightly lighter maximum allowable trigger pull.

No, the M4A1 and M4 use the same barrel.

The RO921HB uses the midweight barrel.

I thought the M4A1 got the heavier "SOCOM" barrel in FY 2001?

Posted: 9/12/2005 2:35:03 PM EDT

[#8]

speaking of which- someone wanted pictures of the israeli m4s that were stamped property of us govt. I have those pictures but forgot who wanted me to post em- please im me.

Posted: 9/12/2005 3:38:07 PM EDT

[#9]

Quoted:
Quoted:
I thought the M4A1 was the model # 927...wich model is the 927

There are several Colt products that are rollmarked M4

However the two I listed are the only two that are offically known as M4 and M4A1 and have US Property marks on them.

For example,

The MT6400, RO977, LE6920, etc. are all rollmarked M4 in some way, but they are not USGI weapons.

The RO977 and RO979 are equivalent to the RO920 and RO921 except they do not have US property marks.

Not to mention the RO777 and RO779 fixed c/h models.
Got that straight from the Colt website.

Posted: 9/12/2005 4:14:34 PM EDT

[#10]

I've never heard of any M4A1's as of late that have standard M4 barrels. It's my understanding that they switched over to the SOCOM barrel specs which required a medium profile under the handguards.

M4- Three round burst, standard profile M4 barrel.
M4A1- Full auto, medium profile M4 barrel.

The early M4A1's did have the standard M4 barrel, but I've always heard that they ditched it for the newer medium profile M4 barrel.

Posted: 9/12/2005 4:33:11 PM EDT

[#11]

Quoted:
I've never heard of any M4A1's as of late that have standard M4 barrels. It's my understanding that they switched over to the SOCOM barrel specs which required a medium profile under the handguards.

M4- Three round burst, standard profile M4 barrel.
M4A1- Full auto, medium profile M4 barrel.

The early M4A1's did have the standard M4 barrel, but I've always heard that they ditched it for the newer medium profile M4 barrel.

So the "SOCOM" M4 barrel is only for the M4A1's? Why the change?

Posted: 9/12/2005 4:52:21 PM EDT

[#12]

Quoted:
Quoted:
I've never heard of any M4A1's as of late that have standard M4 barrels. It's my understanding that they switched over to the SOCOM barrel specs which required a medium profile under the handguards.

M4- Three round burst, standard profile M4 barrel.
M4A1- Full auto, medium profile M4 barrel.

The early M4A1's did have the standard M4 barrel, but I've always heard that they ditched it for the newer medium profile M4 barrel.

So the "SOCOM" M4 barrel is only for the M4A1's? Why the change?

The heavier barrel handles the heat from full auto better.

Posted: 9/12/2005 6:50:02 PM EDT

[#13]

Quoted:
I've never heard of any M4A1's as of late that have standard M4 barrels. It's my understanding that they switched over to the SOCOM barrel specs which required a medium profile under the handguards.

M4- Three round burst, standard profile M4 barrel.
M4A1- Full auto, medium profile M4 barrel.

The early M4A1's did have the standard M4 barrel, but I've always heard that they ditched it for the newer medium profile M4 barrel.

The midweight barrel is standard now on a M4A1. It appeared in 2001 and became standard in 2003 with the regular barrel as an option in 2003.

I should have mentioned/clarified that earlier.

That is why there is a RO921 and RO921HB.

The military doesn't distinguish between the two. They are both USGI M4A1s, but there are two Colt model numbers for them.

Posted: 9/12/2005 6:53:24 PM EDT

[#14]

So technically Combat_Jack was correct after 2001~2003.

I like to use the following designations so to clarifiy everthing.

M4
M4A1
M4A1HB

Even though there is no such thing as a the designation "M4A1HB" in the military.

Posted: 9/12/2005 7:23:31 PM EDT

[#15]

M4A1

Posted: 9/12/2005 7:25:51 PM EDT

[#16]

Quoted:
M4A1
img.photobucket.com/albums/v607/luckyvbar/100_0216.jpg

Now, where, oh where didja get that?
Uncle Sugar lend it to you?

Posted: 9/12/2005 7:29:59 PM EDT

[#17]

No
My buddies demo rifle.

Posted: 9/12/2005 7:32:56 PM EDT

[#18]

I did four mag dumps in a row from a DOE M4A1 this spring....with their ammo even!

Good times.

Posted: 9/12/2005 7:34:31 PM EDT

[#19]

That ain't no M4!!!!
That's a thing of beauty!

Posted: 9/13/2005 7:57:05 AM EDT

[#20]

Okay, so if the M4 and M4A1 now are the 920 and 921/HB, what was the M4 before? The rifles that were designated XM4 and those initially adopted as M4 were definitly not detachable carry handle guns, and were seen with both S-1-3 and S-1-F trigger groups.

Posted: 9/13/2005 8:19:07 AM EDT

[#21]

Quoted:
The military doesn't distinguish between the two. They are both USGI M4A1s, but there are two Colt model numbers for them.

Agreed, Colt's model numbers are typically more descriptive then military nomenclature. Here is a RO921HB box label (M4A1):

Quoted:
Okay, so if the M4 and M4A1 now are the 920 and 921/HB, what was the M4 before? The rifles that were designated XM4 and those initially adopted as M4 were definitly not detachable carry handle guns, and were seen with both S-1-3 and S-1-F trigger groups.

The first M4 contract was awarded in 1994:

www.colt.com/law/history.asp

The burst carbines were M4's, and the full auto M4A1's, same as today. There were a few (about) 2,000 delivered with fixed carry handles (flat top not standardized until 1995). Don't know the Colt's model name for the carbines they delivered in 94/95 with fixed carry handles.

In regards to carbines delivered prior to the 1994 M4 contract we debated what these were called here:

ar15.com/forums/topic.html?b=3&f=118&t=245465&page=3

Here is a picture of some M16A2 Carbines in service in Somalia:

I am inclined to refer to them as M16A2 Carbines, in that is the roll mark. The MOD pattern room has an example of one of these, just like pictured above, Tokoi refered to it as a Colt's Model 727.

ETA:

Forgot that I have a 1990's Colt's Carbine manual, I will check and see if it has model numbers listed.

Posted: 9/13/2005 8:38:17 AM EDT

[#22]

Quoted:
Okay, so if the M4 and M4A1 now are the 920 and 921/HB, what was the M4 before? The rifles that were designated XM4 and those initially adopted as M4 were definitly not detachable carry handle guns, and were seen with both S-1-3 and S-1-F trigger groups.

There was never any now and before. Just because you have a carbine in US mil service does not make it an M4 or M4A1.

Posted: 9/13/2005 8:43:10 AM EDT

[#23]

Well seeing as the way we're making it out to be that the M4 is the 920 and the M4A1 is the 921/921HB, there's gotta be something very akin to now and before, because the US Army FMs and TMs show M4s as fixed carry handle, and the 920 has a detachable one.

Edit- Well, going back to the TM after that it appears I was wrong, but I still thought that original XM4s were flat top guns. A generally held belief is that the original XM4/M4s were 720s or 727s. I had heard 777 as well, but it would appear that is erroneous. Colt does a good job of designating identical guns differently depending on whether they are for the US government or for export/commercial sale, and the 777 is definitly an export/commercial model.

Posted: 9/13/2005 8:51:46 AM EDT

[#24]

I thought the M4A1's had a heavier barrel than the M4 to make up for the high heat encountered in FA fire.

Posted: 9/14/2005 10:31:33 AM EDT

[#25]

When the Military start using the SOCOM M4 barrel? What is the weight differences between the M4 barrel and the SOCOM M4 barrel?

Posted: 9/14/2005 11:13:37 AM EDT

[#26]

Quoted:
No
My buddies demo rifle.

OH? I thought you got that in a LE6920 box. By accident.

Remember?

Posted: 9/14/2005 12:48:16 PM EDT

[#27]

Quoted:
When the Military start using the SOCOM M4 barrel? What is the weight differences between the M4 barrel and the SOCOM M4 barrel?

+4 ounces, IIRC

Posted: 9/14/2005 1:07:49 PM EDT

[#28]

Is the military still using any fixed carry handle M4's? I havent seen any personally. They've all been removable.

Posted: 9/14/2005 1:08:33 PM EDT

[#29]

Quoted:
Quoted:
Quoted:
I've never heard of any M4A1's as of late that have standard M4 barrels. It's my understanding that they switched over to the SOCOM barrel specs which required a medium profile under the handguards.

M4- Three round burst, standard profile M4 barrel.
M4A1- Full auto, medium profile M4 barrel.

The early M4A1's did have the standard M4 barrel, but I've always heard that they ditched it for the newer medium profile M4 barrel.

So the "SOCOM" M4 barrel is only for the M4A1's? Why the change?

The heavier barrel handles the heat from full auto better.

So I'm guessing FA is used alot among those who are issued M4A1's.