Semi-auto vs full-auto

O

odugrad

New member
So I contacted one of the more prominent AR15 manufacturers and asked them what parts would be different from their semi and full-auto rifles, other than the fact that one is full-auto. I assume they use the same bcg, buffer, buffer spring, lower parts. They informed me that they weren't at liberty to discuss.

Which brings to me my question: what is the difference in parts? Gas port size? Also, why would a company not be at liberty to discuss?

Thanks!
 
9

9x19

New member
No idea who you were talking with, but put yourself in their shoes... sounds like they are just being cautious... so many events in today's world certainly encourages it. :cool:

Depending on the maker, between a semi and select fire model, there can be differences in the bolt carrier and lower receiver machining, as well as needing an auto-sear in the lower.
 
T

TXAZ

New member
Why wouldn't they tell you?

Of what business advantage is it to them to tell you? It cost them money to take someone off their real job to help you.

You could be a competitor.

You could be a "non-US Citizen", for which it could be a felony for them to provide you with technical data, if the company has US facilities.

You could be a terrorist sympathizer or nut case, which may not make their actions criminal, but very expensive in civil litigation should that conversation be linked to a crime.

It may also be that the two weapons are different designs / designers on the inside and totally unrelated.

They may have licensed technology they do not own and are not allowed to disclose.

They may have an agreement with a government entity to not disclose technical data to anyone. (This is pretty common)

So tell me, can you give a good reason why they would they want to help you?
 
O

odugrad

New member
I can't think of any reason they'd want to help me. I guess I wasn't thinking in terms of technical data. I was just looking for a very general bit of information.

I wasn't looking at sizes of gas ports, dimensions of this or that.

And I didn't approach it thinking of things from this perspective. I know I'm not a competitor, terrorist, foreigner, etc. but they don't.

But it makes sense. I wouldn't want to divulge my secrets either.
 
C

CALAMBE

New member
The main difference would be BCG, making it tougher and better able to withstand high heat and high stress.
 
H

highpower3006

New member
Full auto parts on an AR that can be used on a semi auto rifle (but usually are not) are, hammer, disconnecter, trigger and bolt carrier. I have heard there is some discussion as to whether the safety with auto cam is legal (although I don't see why it wouldn't be.

Full auto parts that are NOT okay are the auto sear and having the receiver drilled for the sear pin.

The difference between the fire control group on a full vs semi auto are a hook on the rear of the hammer to catch the auto sear, longer disconnector and disconnector notch in the trigger. The safety has a cam on it that pushes the disconnector out of battery with the semi notch on the hammer.

The bottom of the bolt carrier is designed to trip the auto sear as the bolt moves into battery.

Production civilian semi auto rifles will not have the auto fire control group, but usually will have the (slightly) heavier auto bolt.
 
O

odugrad

New member
Thanks, HighPower. That's the kind of information I was looking for. I was just looking to get a general sense of the differences.

Do you know if they'll run heavier buffers on select fire rifles?
 
2

243winxb

New member
HP covered it. Heres a photo of it. Colt M16A1 carbine i sold a while back.
th_M16A1_20080820_02.jpg
[/URL][/IMG] click for larger view.
 
K

kcub

New member
Full auto is overrated in assault rifles. Hard to keep on target. Subguns are easier to keep on target and more fun.
 
4

44 AMP

Staff
Full auto parts on an AR that can be used on a semi auto rifle (but usually are not) are, hammer, disconnecter, trigger and bolt carrier. I have heard there is some discussion as to whether the safety with auto cam is legal (although I don't see why it wouldn't be.
Click to expand...

There is a significant difference between the parts that will work, and the parts that are LEGAL.

There are localities where any, even one of the full auto parts in the gun are not considered legal, despite the fact that the gun does not full auto fire. Look at places that sell M16 (not AR15) hammers, triggers, etc., and see the places they will not ship to for some idea.

Check you local as well as federal laws. Also be aware that despite our freedom of speech, discussing certain details of machinegun construction can violate some laws, particularly when you don't know who you are really talking to.

It is a tricky technical situation, and legally what is, and is not a machine gun is up to the ATF, and if you dispute that, a court.

Mechanically, all the FA parts are needed for FA fire. However, interpretation of what is and what is not legal, and where, does not rely entirely on the mechanical function. It ought to, but everyone does not share this opinion, which is why many people wind up in court over FA issues.
 
O

odugrad

New member
I became more curious because the other day I had a chance to fire an MK18 SBR on full-auto and a Colt 9mm submachine gun (I'm guessing that's what it's called).

You're right, the MK18 was very difficult to keep on target. Much more than I would have thought. I ended up primarily shooting 3-round bursts. The MK18 was work to shoot, the Colt, however, was an absolute pleasure to shoot.
 
R

Road_Clam

New member
The "Class III" guys are their own circle. No uneducated novice outsiders are allowed. The Class III owners have spent a lot of time and money to LEGALLY posses registered Class III firearms. They also are closely monitored by the BATF. If you ask "What parts are different between semi and full auto" red flags immediately go up and now you are a threat. The Class III crew never talk full auto via the internet as it will just fester stupid and threatening questions by the unknowing. So the moral of this story is if you hear one at your local range, just respectfully admire it's coolness, don't ask questions and just leave it at that.
 
O

Ocraknife

New member
Check you local as well as federal laws. Also be aware that despite our freedom of speech, discussing certain details of machinegun construction can violate some laws, particularly when you don't know who you are really talking to.
Click to expand...

Which laws would be violated?
 
K

kcub

New member
The "Class III" guys are their own circle. No uneducated novice outsiders are allowed. The Class III owners have spent a lot of time and money to LEGALLY posses registered Class III firearms. They also are closely monitored by the BATF. If you ask "What parts are different between semi and full auto" red flags immediately go up and now you are a threat. The Class III crew never talk full auto via the internet as it will just fester stupid and threatening questions by the unknowing. So the moral of this story is if you hear one at your local range, just respectfully admire it's coolness, don't ask questions and just leave it at that.
__________________
Click to expand...

Baloney
 
C

CaptainO

Moderator
This "aura of fear" is exactly what the government wants "prohibition and secrecy". how do you think the Federal Government got away with running guns to the Mexican drug cartels?

We are giving them what they want. More power.
 
R

reynolds357

New member
The BATFE published a bulletin a while back that in essence said that full auto parts that did not in any way make a semi auto function as a full auto were legal. Basically, the only thing illegal would be the auto sear or home made variations of it.
 
M

Model12Win

Moderator
Full auto is for action movies heroes and camel jockeys.

You don't need it.

Aimed, semi-automatic fire is far more effective. Full auto is a waste of ammo in all but the most extreme of circumstances. This is especially true for full power "battle rifles" in cartridges like 7.62x51mm.
 
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