I can't decide between getting a full size AR-15A2 or an M4. You see I am planning on becoming a marine and I was thinking about getting the full size version to become familiar with it before going in the military since that is the basic rifle. I don't want to shoot less than expert at boot. On the other hand I really like the M4, it's just bad azzzzz.
Is there that much difference in the feal between them? Would the M4 be just as good as the full size for preparing me? What should I go with?

The Air Force.

No matter what you buy or get now will be what you have to qualify with! some of these guns you get from the armory are damn near shot out! so the scores you get are not neccesarly your best shooting skills.   i shot expert with the M1 but only sharpshooter with the M1A  ,,  does that mean i lost my eye with the upgrade!  not so i could hit a pop up target at 460meters with a peep site!  what a thrill to see that target drop at that range!  well you know the range needed to engauge a target got shorter.. so in reply to your post if you buy a quality ar/15 and become an ace with it, you may very well get a rifle of less quality and not shoot as well in basic.  so just give it your best ,and keep that in mind................An't no pop up targets in somalia!,,,,,,,

Tac45, I  had the benifit of handling an AR15A2 before boot camp and it was a definate help.  The rifle you will be issued will most likely be ugly but fully capable of shooting expert.  Buy a rifle with the A2 barrel, not the HBAR.  The HBAR feels very different in you hand and you want weapon FAMILIARITY.  If you aren't getting help from a CMP service rifle shooter or a former Marine who regularly shot expert with an A2, don't shoot your new rifle.  Walk around the woods with it, take it apart, take long hot showers with it, but don't shoot.  The more shooting you do will hold you back during qualification.  You are going to have to unlearn a lot of bad habbits  Expert shooters in boot camp are kids who weren't deer hunters, "shot my dad's guns all the time", they come with no bad habbits.  Shooting at a range does not make one a "target shooter".  I used to coach for my regiment during qualifications.  I always found that people who listened well (women and non-civilian shooters) were far easier to coach.  Talk to some people shooting service rifle or recent veterans.  More important than getting a rifle before you go in is getting in shape, learning general orders, etc.  Shoot me an email if you have more questions.

tac45, your qualifier about joining the Marines sort of dictates the M15A2 choice.  Except for that the M15A4 gives vastly more scoping and mounting options.

Now you may not be aware of this but the Marines go camping a lot.  I've heard they even sleep outside !  (They also eat something called "MNRE's" - meals-never-ready-to eat.)

Plainly you need to re-think your military decision and pick the NAVY - specifically the Submarine Service.

Not that we didn't have it tough in Subs too.  I remember the week we only had steak three times !

MRE=Meals Rejected by Ethiopians

Why would you want to join the Marines?  
It's a hard life.

If I had to do it all over again, I'd still have joined the Air Force, with the Navy as my second choice.  Army third, Marines fourth.

The Air Force's version of 'roughing it' is having to go without cable TV in an air-conditioned communications trailer that's got a well-stocked fridge and a comfortable bunk.  You have to settle for TV via satellite, instead.   If it gets really bad, the air conditioner may crap out.

Get an aircrew position and life will always be fun and interesting.  Seeing the world go by far below you is incessantly cool.  

One enlisted Air Force job I'd like to have had would be refueling boom operator, on a KC-135 tanker.  Whatta view!  It helps that I'm a total aviation nut.

Among Navy jobs, any flight deck job on a carrier would be both dangerous and interesting. Thumbs up...but don't let it get knocked off by the wing of an F/A-18!

As for choosing a rifle, an AR-15A2 would be the correct choice, but it would be more important to get shooting instruction from a Marine who will show you the Marine way of doing it. Those guys DO know how to shoot properly, and you may not even know what bad shooting habits you have that need to be disposed of.  Get that help, and you will not regret it, no matter what service you go into.  

Time spent at the range in boot camp will be the most enjoyable days at boot camp, and if you don't have any bad habits that get you yelled at, but shoot clean, straight, and better than anybody else, it certainly won't hurt your standing with your instructors!

CJ

Quoted: .... but it would be more important to get shooting instruction from a Marine who will show you the Marine way of doing it. Those guys DO know how to shoot properly, and you may not even know what bad shooting habits you have that need to be disposed of.     Time spent at the range in boot camp will be the most enjoyable days at boot camp, and if you don't have any bad habits that get you yelled at, but shoot clean, straight, and better than anybody else, it certainly won't hurt your standing with your instructors! CJ

CJ,
your advice is right on point.  (The right way, the wrong way and the Marine way.........)

I'd say go with the M4, but you have probably already figured that I would say that. Parts on the M16A2 and the M4 are 85% interchangeable. Both function the same. There is talk of the military replacing all M16A2's with M4's eventually. Since it will be your personal weapon, get the one you like the best. It probably will not influence your shooting in boot camp either way.

I suggest the full-size rifle.  For a couple of reasons.  

1.  Your indication that you will be going into the military.  You will most likely get issued a M16A2.  Familiarity will help here.

2.  I personally do not like the shorter barrelled ARs.  Yeah, the look cool, but do some studying on the relationship between barrel length and effectiveness of the 5.56mm round.  As you reduce barrel length, the velocity goes down.  The ONE thing the 5.56mm round has going for it is VELOCITY.  Why would you want to sacrifice the round's primary reason for effectiveness for coolness?

i come from a military family, Army mostly but  i went Marine. unlike the other services Marine rifle range is 2 weeks long. youll do fine. typically the best shooters are the ones who've never seen a rifle before but are confident in their ability to learn. you will gain no advantage by being familiar with the rifle. all you will do is learn how to handle it incorrectly so you can get yelled at. by the time you reach the rifle range on PI you will have had that rifle within one arms length for 10 weeks. trust me, youll be familiar with it. and during periods of instruction about the rifle, its use and it's care, you will be expected to move in baby steps with the rest of the recruits. go ahead and be the guy that thinks he knows how to take it apart and gets ahead of the DI, you'll be playing in the sand pit for an hour while the rest of the platoon is hearing "this is called the bolt... scrub it now" also, living in the barracks and owning a firearm is such a galactic pain in the ass you'd never get to see it. it must be kept in the MP armory and they will act like its a major inconvienience to get it for you, and forget taking it to the barracks to clean it. VERBOTEN!
  my advice is to wait until after you're a Marine and you live off base and purchase your AR.

 cmjohnson had it right...the AF is soft but they do an important job it just depends on what job you want to do. AF quality of life is leaps and bounds above that in the Corps but you know what? get stationed at an AF base and watch those bitches part like the red sea when one or two of you walk in the E club. intangible benefit! i recommend 2 books, Tom Clancy's "Marine" which gives a lot of detail on the culture and ethos that is found only in the Corps and "Making the Corps" by Thomas Ricks. should only set you back about $20 and will help you decide if you pack the gear to serve in my beloved Corps.
 

I guess it depends on your body shape.  I'm skinny and I don't have long arms.  Converting my AR15A2 to M4gery (16" flat top w/ non collapsible stock) made the rifle shorter and much more easier to handle.  

I don't want to make waves, but I disagree with some posts here about not shooting for fear of forming bad habits.  I do agree with the idea that no potential soldier should attempt to learn the proper care and maintenance of his rifle before boot camp.  Almost anyone can learn by shooting, but there is no need to force the instructors to unlearn the recruits' ideas about maintaining a combat weapon.  I mean learn shooting all you can, but let the military teach you the rest.  

My brother, as well as I, learned to shoot AR's when we were in grade school.  He is now in the US Army at Ft. Hood in the Sig and qualified as Expert with the M-16.  He attributes this to his experience shooting AR's.  While I have great respect for the men who train our soldiers to shoot, he told me of some fairly dumb "facts" he was told by some of the instructors.  We all know the classic .223 bullet tumbling after leaving the barrel, etc...  Of course he could not argue with them, since he would get smoked.

Just my .02  

Of course this is the US Army I am talking about and not the Marines.

If you want to shoot expert, put all guns away, and have a doctor remove all memories of shooting from your brain.  The only people who scored Expert in my Basic Training Company (Ft. Leonard Wood, MO, Class of 1999) were the people who never shot a firearm before in their life (I was two shots away!!  Waaaaahhhhhh!!!!!)
In training, you'll have a full size M-16, but you might end up differntly once you are out of training.  My Guard unit is getting M4's now, and when a Guard unit gets the equipment, you know the active army guys are going to get it (based on your MOS and mission of course)  It didn't apply to me, I ended up as the gunner on our Humvee, so it's SAWs and MK-19s for me.  
The Air Farce does indeed have a cushy life.  We went to Italy on a two week rotation, there were some Air Farce guys living in our barracks, they were getting extra money for living in substandard housing, the same barracks we were staying in for no extra money.  

Hey, I’m a 24yr old former Army ROTC cadet who’ll be shipping out for enlisted Basic in October for the Army
National Guard. I’ve been shooting since I was fourteen, and all but a few of the, now hundreds of guns, I’ve owned
Have been military types. In 1995 the Army ROTC program sent me to a nine week ‘camp challenge’ at Ft. Knox, KY to qualify for a scholarship. During those nine weeks we went through a basic type course, save for a more relaxed curriculum and more pleasant Drill Sergeants. Our training unit was a real one, the 1st Bn. 46th Inf., and we did everything that I’ll do as an enlisted trainee. As so many others on here have said, my shooting skills did nothing to improve my skills on the range, in fact I’d say they were a big liability. But…

I too am building a AR-15 and intend on using it as a training implement to brush up on care and handling of the weapon, just as I will begin running and practicing obstacle course exercises that I know I have trouble with once the snow melts around here. My biggest problems with qualifying with the M-16 (other than my training weapon, named “Petra,” after a girl who broke up with me a week before I came home, was crap) was that the way I had learned as a civilian to shoot, was completely different than the way the Army teaches.

Get a hold of someone who has recently (I.E. with in the past five years) graduated the USMC program that you are going to go through. Have them teach you the positions that the Marines will require you to shoot from. For me, shooting from an unsupported prone position on a gravel surface was pure hell. Especially on the pop up targets at varied ranges, it shredded my elbows, and no matter how light the AR or how strong you are, by the end of the day on the range you’ll be fighting to keep from shaking when you’re on the sights. No doubt the USMC has a better marksmanship program than the Army, but still, its written in a book that is available to you right now (a FM or a TM, field manual or training manual.) If you can get a hold of the manual, you can train with it. May be not totally, but it’ll give you a good idea what will get you gigged, and what will get you left alone. And being left alone is golden.

The final bit of advice I’ve got for you is general. Most DI’s I’ve met, former and current, are cut from the same cloth all good teachers are cut from, and they care deeply for their students and the ultimate cause they serve. The pressure they will put on you is to make sure you survive if things get ugly. Every push-up, every crap-detail you pull, every do-over you get for a fubar, is a lesson that could save you in the field. Never quit. Never ever quit. If you cant go over or around, you can always go under or through. When things get tough….FIDO, F* it, Drive On.

God Bless you for going into the Corps, my father's brother served five tours in Vietnam and twenty years in the Corps overall. From Private to Major, including a Drill. Finest soldier I’ve ever met.