AR15 vs M4 - What's the difference?

[freddy g]

besides the shorter length of the military M4 barrel, its realy the contour of the barrel that makes it an M4 barrel or a government profile barrel,so if it's got a colapsing stock,flat top, M4 hand gaurds,16" M4 profiled barrel it's as close as a real M4 as im gonna get

[adsstorm]

The AR stands for armalight which eugene stoner the designer of the first CAR (carbine armalight) worked for at the time he designed it. The first rifle was actually A 7.62 nato yet the military wanted the 5.56 for what ever reason. when the military picked up the design they designated it the m16 and somewhere along the line the patten was given to colt to mass produce these rifles. Yet over the years due to the military's designators of weapons and the models sold to civilians (retrictions placed on manufacturers by law) you will find a wide variety of what is an M4 or what is an M16. You can take the receiver of a full auto (busrt cam) m16a2 change out the hammer, trigger, disconnector, selector switch, and remove the auto sear and replace them with semi only hammer, trigger, disconnector, and selector switch and technicelly have a civilian legal fire arm. Another problem is that during the assault ban rifle years, colt in particular, went to great pains to make it to where you could not change out some of the parts like changing the diameters of the take down pins so lowers and uppers could not be switched and bolt carriers were shaved and machined so that a full auto sear could not be used in a civilian bolt. That kind of thing. Barrel lenghts can also be a determining factor in what a full auto, three round burst, or semi only rifle can be designated. Yet the reality is that you can put a fixed stock on an m4 like that of an m16 or have full auto, three round busrt, or semi parts inside of the lower recierver. Yet the stamp on the outside will m16a1 or m16a2 or maybe Ar-15 LE only. believe me when I say that if you are a government entity and you have M4 rifles the receivers may say that it is an m16a2. Which are parts that have been recycled through the system and the parts where a diffrent rifle in a past life.

[okieco]

Don't forget the CAR15. My first AR which I purchased back in 80' something was a CAR15. It was an AR15 with an 11.5" heavy barrel and it had a perminantly attached flash suppresor which was approximately 5" in length. Because it was perminantly attached it was considered legal. Most of these had the retractable stock however mine did not. Mine had a standard fixed butt stock which was my choice. This was not an A-2 upper and did not have the fully adjustable rear sight. It had the short round handguards with the heat shields.

[BimmerJon]

AR15: pew....pew....pew
M4: pewpewpewpewpew

[Dwal001]

Hello Out there. This is my first post to this forum. There seems to be a lot of great answers to questions brought up here. I don't think anyone has hit on the feed ramps difference. I do know the difference between the two do I would like to ask a question about M4 feed ramps vs AR15 feed ramps. Would the M4 feed ramp dictate if it was an M4 or vice versa with AR 15 feed ramps. Does the difference all have to do with barrel length and the stock? Doing my research on the ramps most are saying no difference but some are saying M4 ramps are more dependable from hang up. I just ordered a 24" barrel with M4 ramps. I'm going for long distance accuracy.
Thanks for any feedback.
Dwal

[Splittiebus66]

Hello Dwal, welcome.

[Solaran_X]

Mark is correct. The M4s are 14.5 inch barrel select-fire carbines that the Army uses. The M16 is a 20 inch select-fire.

Anything civilian owned is an AR-15 unless your lucky enough to have access to NFA toys.

What about Colt's actual S/A "M4 CARBINE"s like the LE6920 and LE6970?

[Kabloosh]

The M4 is merely the military designation of the carbine length AR-15

Internally just about everything is interchangeable from a milspec AR to an M4 save for the fire selector switch which would require some machining in the lower receiver of an AR-15. Do that properly and you can switch out the fire selector switch and become a felon unless you have a manufacturing license to do so.

There are some differences in an M4 compared to an M16 but around 85% of the parts are interchangeable. The key part would be the M4 feed ramps. Due to the shorter gas system and how the gun operates on full auto fire an M4 could have feeding issues without the specialized ramps.

[Solaran_X]

The M4 is merely the military designation of the carbine length AR-15

Internally just about everything is interchangeable from a milspec AR to an M4 save for the fire selector switch which would require some machining in the lower receiver of an AR-15. Do that properly and you can switch out the fire selector switch and become a felon unless you have a manufacturing license to do so.
There are some differences in an M4 compared to an M16 but around 85% of the parts are interchangeable. The key part would be the M4 feed ramps. Due to the shorter gas system and how the gun operates on full auto fire an M4 could have feeding issues without the specialized ramps.

Actually, you'd need a full F/A or burst fire control group - not just the selector.

Selector.

Auto sear.

Hammer with the sear hook.

And I think the trigger is different as well.

[ungawa]

Moar hole.