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Old February 1, 2013, 04:06 AM   #1
pumkin
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whats M4 mean on a lower AR 15

I'm just starting to understand some of the terminology and what abbreviations stand for on ARs. A shop told me there stripped lower reciever are an M4. I asked what that meant, he explained, but I didn't comprehend. The guy was busy, I didn't want him to know I was green, and just left it at that. I used to think M4 stood for the design of the barrel. The kind w/ a bayonet lug and thicker walled at end of barrel. And I still kinda think that. Then I found that M4 stood for a flat top upper receiver.

Now I'm lost, being I'm was told that these stripped lower receivers are M4 lower receivers. So what makes a lower receiver an M4? Are stripped M4 lowers milspec? If what I'm desribing is true, can you put any type of milspec upper on this so called M4 lower? I'm hoping you guys can straighten me out on what M4 is about, and what parts it applys to. thanks.
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Old February 1, 2013, 05:05 AM   #2
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"M4" is the military's designation for the current issue assault rifle. Any semi-auto equivalent is an ar15. Sometimes guys will call their 16" barreled collapsible stock rifles an M4 to distinguish it as set up like an M4 but this is technically incorrect.

The flat top uppers are sometimes referred to as "A3" as in M16a3 because the A3's were the generations were the first to use the flat top. An A2 would be a fixed carry handle with the updated sights of the M16a2 and basically be configured just like an M16a2. Same goes for an A1.

More often than not "milspec" is just thrown around as a buzzword to sell product, not always but usually. Most AR15 stripped lowers are as good as the next and to be a true AR15 receiver it would have to be to the same dimensions as any other receiver. And any AR15 upper should mate to any lower.
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Old February 1, 2013, 05:05 AM   #3
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Hmmm. Maybe he meant it could build an M4?

A stripped lower is just that. It can be used to build any AR type rifle or pistol.
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Old February 1, 2013, 07:36 AM   #4
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The caliber stampings or other "descriptive" markings on the lowers mean nothing-just marketing. Name/address of maker and SN are required but the rest is advertising.
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Old February 1, 2013, 10:52 AM   #5
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Unless the lowers were milspec lowers intended for use with a three-position selector lever, they're not true M4 lowers. A true "M4" is the military carbine version that's capable of full-auto or burst. That said, "M4" is a marketing term thrown around by many manufacturers of AR-15s.

The terms marked on lower receivers normally mean absolutely nothing. For example, some standard Colt 6920s come with lower receivers stamped "Law Enforcement Carbine", some are marked "Sporter", some are marked "M4 Carbine Sporter", and some are marked "M4 Carbine". What's the difference between those rifles? Absolutely nothing at all, other than the markings on the lower.
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Old February 1, 2013, 12:29 PM   #6
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Unless it had a $10,000 price tag it wasn't a real M4 lower.
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Old February 1, 2013, 03:20 PM   #7
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The military M16 is a 20 inch barrel fixed stock rifle. The M4 is 14.5" barrel collapsible stock carbine. There is absolutely no difference in the lower receivers or the upper receivers. I think the guy behind the counter was full of something that rhymes with spit.
Quote:
"M4" is the military's designation for the current issue assault rifle. Any semi-auto equivalent is an ar15. Sometimes guys will call their 16" barreled collapsible stock rifles an M4 to distinguish it as set up like an M4 but this is technically incorrect.
Bighoss, I have to clear up a few things here. First of all the Army does not designate either the M16 or M4 as an assault rifle, never did. Second AR15 is a name that is patented to Colt and no one else is legally allowed to use it. People call their AR15 looking rifles ARs but if you will notice, none of them except Colt actually say AR anywhere on them. Bushmaster tried it and got sued by Colt and lost. Finally AR15 can be the civilian equivalent of either the M16 or the M4 but to get really technical about it when the AR15 first was marketed to the civilian world, there was no M4 invented yet. I don't think the A1 version had even come out yet. They were still to the best of my knowledge minus the chrome bore or forward assist.
Mforgery is a better nick name for the civilian Semi auto version of the M4.

Last edited by CTS; February 1, 2013 at 04:04 PM.
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Old February 1, 2013, 04:51 PM   #8
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Well if he was selling it for less than $4000 then it probably was just a standard milspec AR lower receiver - and he was using an improper term. Now if it was a complete lower then M4 could mean it has a standard collapsing stock like an M4.

Lazy term on his part anyway, so don't be ashamed to have him describe exactly what it is. Call, if it's 7075-T6 alloy and the price is good you might want to get over there quick if you need one.
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Old February 1, 2013, 05:32 PM   #9
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Quote:
I have to clear up a few things here. First of all the Army does not designate either the M16 or M4 as an assault rifle, never did.
I couldn't tell you if they designate either as such, but those rifles definitely fit the US Army's definition of "assault rifle."
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Old February 1, 2013, 07:39 PM   #10
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Could you show me where you are getting the US Army's definition of an assault rifle? I joined the Army in 1976 and then switched to the Coast Guard and finally got out in 1988 and I never heard the term "Assault Rifle" used in my life until around the early '90s and that was being used by Politicians and the media.
http://www.armystudyguide.com/conten...dy-guide.shtml
Check out item 21 in the above linked Study guide. This is the definition I was taught (minus the 3 round burst part, cause we had A1s that were full auto or semi).
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Old February 1, 2013, 07:41 PM   #11
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My Windham Weaponry has an M4 designation for the model.

http://windhamweaponry.com/pdf/Updat...SRPPRICING.pdf
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Old February 1, 2013, 07:47 PM   #12
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Quote:
My Windham Weaponry has an M4 designation for the model.
Well, kind of. They managed to sneak the m4 in there with R16M4STT but it's not like it says model: M4A3 or anything.
Kind of like Rock River and their LAR15 because they can't legally call it an AR15.
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Old February 1, 2013, 09:50 PM   #13
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Quote:
Could you show me where you are getting the US Army's definition of an assault rifle?
Both rifles fit the definition of "assault rifle" that's existed since the first once was invented in 1944. But I suppose only the M4 fits the US Army's definition:

The US Army defines assault rifles as "short, compact, selective-fire weapons that fire a cartridge intermediate in power between submachinegun and rifle cartridges."

-From Wikipedia
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Old February 1, 2013, 11:06 PM   #14
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So wikipedia defines it as a short compact... show me a link to any US Army pub that calls it an assault rifle if you can. The STG 44 was a Machine Pistol or submachine gun that fired a 7.92x33 kurz aka Pistolenpatrone M43 (pistol cartridge model 1943),

Last edited by CTS; February 1, 2013 at 11:43 PM.
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Old February 2, 2013, 01:46 AM   #15
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Quote:
I never heard the term "Assault Rifle" used in my life until around the early '90s and that was being used by Politicians and the media.
You're thinking of the BS media and political term "assault weapon". The term "assault rifle" was coined by the Germans (in German of course) at the end of WW2. It referred to a select-fire rifle firing an intermediate-power rifle cartridge. The STG-44 is widely considered the first assault rifle.

Quote:
So that is how the Army defines it according to wikipedia? That doesn't even make sense. A submachine gun shoots a pistol cartridge and a rifle shoots a rifle cartridge. There is no intermediate round between pistol and rifle. A 5.56x45NATO round is a rifle cartridge, it was based on a rifle cartridge when it was designed so how could it be between a pistol and a rifle cartridge?
I understand what you're saying, but the 5.56 is considered an intermediate power cartridge compared to full-powered cartridges like the 7.62x51mm.
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Old February 2, 2013, 01:54 AM   #16
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Quote:
So wikipedia defines it as a short compact... show me a link to any US Army pub that calls it an assault rifle if you can.
Here you go:

http://gunfax.com/aw.htm

By the way, I never said the Army calls the M4 an assault rifle. I said the M4 fit the Army's definition of assault rifle.

Quote:
The STG 44 was a Machine Pistol or submachine gun that fired a 7.92x33 kurz aka Pistolenpatrone M43 (pistol cartridge model 1943)
The STG 44 is widely considered to be the worlds first assault rifle. I don't think I need to post any links for this one, it's pretty well known and easy to research.
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Old February 2, 2013, 08:11 AM   #17
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Quote:
By the way, I never said the Army calls the M4 an assault rifle. I said the M4 fit the Army's definition of assault rifle.
but that is what I asked you for and you replied with something from wikipedia.

Quote:
The STG 44 is widely considered to be the worlds first assault rifle. I don't think I need to post any links for this one, it's pretty well known and easy to research.
I agree, but it doesn't fit the very category that you described above does it? Because it shoots a pistol round.

The above Army description describes an AK 47. Doesn't say anything about an M16 or an M4. In case you aren't aware, there are many differences between the two. That is the reason the Soviets finally came out with the AK74 so that they had something that would compete with the 5.56x45 Nato round. The 7.62X39 is an intermediate cartridge even in comparison to the 5.56x45Nato just in velocity alone.

I don't know why you wish to keep up an argument that doesn't really matter anyway. I wanted to clear up a few points that someone mis spoke about, which are common misconceptions of what an AR15 is and you want to jump on me about some media dreamed up name for a rifle that doesn't fit and never has. If you want to go on believing those misconceptions that were dreamed up by the liberal media that is up to you but it doesn't help our cause any as gun owners. We keep saying that the AR15 is not an assault rifle and yet apparently many of you believe that it is the civilian version of an assault rifle. That is a dubious distinction at best. We really need to get on the same page as gun owners here if we ever hope to stand a chance against the gun grabbing left.

Last edited by CTS; February 2, 2013 at 08:33 AM.
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Old February 2, 2013, 10:11 AM   #18
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I recently picked up a Colt 6920 that on both the outside packaging and on the lower receiver it says M4 Carbine. Civillians can't walk into a gun shop and buy a true M4, only M4 style...flat top upper, collapsable stock, barrel cut for mounting a M203 launcher. M4 is really just a marketing thing.

Back when I got into shooting it was explained to me like this...they are all AR15's, some are rifles, some are carbines. The lower receivers internally are all the same, the only difference between them is the buttstocks/buffer tube. When you buy a civillian parts kit for the lower, there is no difference between AR-15 or M4 style, they are all the same. Once upon a time it did matter if the lower was preban or postban as that affected your choice of buttstock and upper receiver features. For a while Colt was using a different size for the pins that held the upper and lower together. Some are mil-spec, some are not.

Functionally they are the same, one shot per trigger pull, they take the same magazines. For some folks having one rollmarked as M4, LE Only, or whatever is desirable and they are willing to pay extra for that.

Last edited by cryogenic419; February 2, 2013 at 10:18 AM.
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Old February 2, 2013, 10:23 AM   #19
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Quote:
I agree, but it doesn't fit the very category that you described above does it? Because it shoots a pistol round.
The 7.92x33mm Kurz is a rifle round. It's the very sort of intermediate-power rifle round that is fired by an assault rifle, along with rounds like the 7.62x39 and the 5.56x45mm

Quote:
I don't know why you wish to keep up an argument that doesn't really matter anyway. I wanted to clear up a few points that someone mis spoke about, which are common misconceptions of what an AR15 is and you want to jump on me about some media dreamed up name for a rifle that doesn't fit and never has. If you want to go on believing those misconceptions that were dreamed up by the liberal media that is up to you but it doesn't help our cause any as gun owners.
You're obviously a little confused here. "Assault rifle" is a term invented by the Germans to describe the STG-44 and is a clearly-defined category of firearms. The military's M4 definitely fits the definition of "assault rifle".

The AR-15 is NOT an assault rifle.

"Assault weapon" is a made-up term by politicians and the anti-gun media.

Understanding the difference between these two terms will help in future debates with people who support the Assault Weapons Ban. It's always great seeing the look on people's faces when I tell them that assault rifles are already all but illegal and "assault weapons" don't exist.
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Old February 2, 2013, 10:29 AM   #20
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pumpkin's question has been answered. If anyone has time to play lawyer here and argue over definitions, that tells me they're not spending enough time on the range. Go shooting. It's fun.
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