AR Sponsor
Posted: 5/25/2007 10:24:14 AM EDT
|
Sorry guys I know that Im probably barking in the wrong yard. Im looking to find technical information regarding how AUTOMATIC WEAPONS work. I know that most are gas driven using some of the gas pressure to shove the bolt back and eject as well as allow the next round to chamber. What I dont get is how specificaly BURST fire works. Everywhere Ive asked (other forums) Ive gotten a bunch of NANCY A$$ed people telling me about the legalities of it and the WHOAS.......... I just happen to be very mechanical and I want to understand how the gun was designed to effectively fire 2, 3 or whatever the number is of rounds and actually stop. SINGLE FIRE...........I GET AUTO FIRE.............I GET SELECTED #...........I dont get. Thanks to anyone who can lead me in the right direction or explain it to me. |
|
There is a ratchet cam in addition to the standard fire control group. Each time the carrier returns into battery, it trips the cam one notch. If the cam is for three-round burst, at the end of the third shot, the cam releases the disconnector to catch the hammer in the cocked position. The problem with burst fire is if you release the trigger before all shots are fired, the next squeeze of the trigger reactivates the cam. So if you fire two shots intead of three, your next "burst" will only be one shot. The 605b had a burst FCG and then the M16A2 was the next to have the burst feature. |
If you haven't seen the parts involved, Bushmaster has a good picture of them here:www.bushmaster.com/shopping/lowers/3shotburstkit.asp |
|
There are different types of burst mechanisms; the M-16A2 type works as described above, i.e. it won't reset until a total of 3 rounds are fired. This means you could have a burst of 3, 2, or 1 round, depending on the position of the ratchet cam. In addition, the M-16A2 burst mechanism affects the trigger pull of the rifle, changing the pull weight as the burst ratchet, which is always engaged, counts off the rounds fired, even on semi-auto. The type of burst mechanism used by Heckler and Koch resets every time the trigger is released, meaning you could fire 2-shot bursts all day long with a rifle set on the 3-shot burst setting. This type of mechanism is far more complex, not surprising considering the manufacturer and country of origin of these weapons! There are other types as well (Romanian AK-74 <safe, full, 3-shot burst, semi> mechanism anyone?!?), these are just the two I am vaguely familiar with. I completely agree with you that this is a fascinating subject, and the solutions that firearms designers come up with are often times downright ingenious. Good luck with your research. 
|
| Don't forget that the Ruger AC556 and FNC also use burst cams. I don't recall if they reset though. I don't mess with the burst groups all that much. I've worked with the M16 burst groups plenty and don't really care for them. You need a PhD to work on the HK burst groups. The AK, FN, and Ruger burst groups are all pretty simple and effective in design. |
|
YOU GUYS KICK SOME SERIOUS ARSE! Other places Ive asked about this always assume that Im up to no good..........makes me angry. Im fascinated by the idea that they came up with a clever device that not only counts but limits firings and they manage to house it in the same weapons as single shot. Thanks for everyones imput and I hope I get a better grasp to the ingenuity that is necessary to have designed this mechanism. |
Yep. Created as a "solution" to lack of training and proper trigger control. |
The RDIAS mimics a real autosear. This autosear is the same for a full auto or 3 round burst set up. So yes, you can use a RDIAS with a burst set up. |
|
Forgive my total and complete ignorance.............but what exactly is a RDIAS???? I gather its a device that converts your ar to a M16 but I was under the impression that the guns were machined differently and while possible, all the gadgets they make for conversions were in fact dangerous IF they worked at all. |
RDIAS = Registered Drop-In Auto Sear It is a small assembly that drops into semi-auto lower receivers to mimic the function of a factory-installed auto sear. Because it mimics the function of the sear only, it must be used with all the pertinent M-16 parts to function properly. But it also should function reliably and safely, since it is performing a function the rifle was originally designed to have. |
|
OK, since people are answering questions here, i have one that's kind of off topic. I undertand the mechanics of a closed bolt full auto gun, but as I was driving home yesterday I was wondering about open bolts. Do they have the same issues as a closed bolt gun where the timing has to be right to keep it from firing out of battery? Is there still a sear that gets tripped each time the bolt cycles until you let off the trigger, or do they just catch on the trigger when you stop? Or am I just WAY off on how an open bolt works? |
|
Here is more then you ever wanted or needed to know: www.quarterbore.com/library/pdf_files/tm9-1005-319-23.pdf Look at PDF pages 207 to 212 for detailed information on how the M16A2 group works. Then read the rest of the manual several times and you will know how the rest of the AR-15 and M-16 works! It really is worth the time to read it! |
AR Sponsor