Mostright60

On 11/22/2015 at 3:48 AM, Collimatrix said:

Most automatic weapons, with the exception of really weird designs like the Madsen LMG and Hino-Komuro, have a linear reciprocating breech member; either the bolt or a bolt carrier group.  This reciprocating member is supposed to move rearward (the recoil stroke) and pull the spent case from the chamber, and then rebound off of a spring to shove a new round into the chamber (the counter-recoil stroke).  After the counter-recoil stroke the reciprocating mass should come to a halt in its forward-most position; the "in-battery" position.  When the bolt carrier group is in battery the case like they are show on this site https://primearmor.us/ is entirely surrounded by the walls of the firing chamber and the locking mechanism is fully engaged, so it is safe to fire.  Things do not always work ideally, however, and sometimes this reciprocating mass bounces instead of coming to rest.  This is called (somewhat erroneously in the case of gas-operated weapons) "bolt-bounce."

 

Andrew Tuohy removed the buffer weights from the buffer in an AR-15 to make the action bouncier for illustrative purposes:

 

 

 

There are two ways that bolt carrier rebound can be a problem.  In extreme cases the bolt carrier will rebound, but a combination of high friction in the action and weak return springs will mean that the bolt carrier gets stuck and does not go back into battery.  Hopefully the designer was smart enough to design the thing so that it absolutely cannot fire when it is out of battery, because out of battery cartridge ignition is an excellent way to convert a firearm into a pipe bomb.  If they were so wise, then there will be a failure to fire of some variety.  Generally speaking a weapon has to be unusually dirty, worn, or poorly designed for this problem to occur.  Return springs are usually strong enough to get the moving parts into battery even if they aren't fully compressed.  I have, however, witnessed this problem in German K43 rifles because they are a pile of suck and fail.

 

http://tonnel-ufo.ru/foto/oruhie/snaiper_3/germani/gewehr_43-4.jpg

 

But they're pretty.

The second, more likely problem only rears its ugly head in fully auto fire.  In most full auto weapons there is an auto-sear, which a secondary sear which releases the hammer as long as the trigger is depressed.  The auto-sear is tripped by the bolt carrier during counter-recoil, usually when or just before the bolt carrier goes into battery.  If the bolt carrier rebounds off the front of the receiver and the timing is just wrong, the hammer (or striker) will hit the bolt carrier when it is slightly out of battery.  Again, competent designs have means of preventing out of battery ignition and the attendant facial and manual reorganization that tends to go with that.  However, when the hammer or striker hits the out of battery bolt carrier its kinetic energy will be spent.  This means a failure to fire.

 

Early M16s had rebound problems, particularly during full auto fire.  Originally the buffer was intended simply to be a hollow spring guide, but a problem with light primer strikes forced a redesign of this component in 1966.

 

http://i.imgur.com/KDQXtGD.png

 

This image, from the patent for the improved buffer shows the series of sliding weights that were added to the buffer.  These work like the sliding pellets in a deadblow hammer and arrest the tendency for the bolt carrier to bounce.  The additional mass had the added benefit of slowing down the velocity of the bolt carrier, which reduced wear on the parts and lowered the cyclic rate of fire, which improved full auto control.

 

The HK roller-retarded blowback guns, owing to their extremely high bolt carrier velocities, have a strong tendency to rebound unless somehow checked.  The solution HK engineers hit on is an anti-rebound claw:

 

http://www.hkparts.net/shop/pc/catalog/hk91boltgroup_2160_large.gif

 

Labeled as the "bolt head locking lever" in this diagram.  This is a spring-loaded claw mounted on the bolt carrier that grabs the bolt head as the bolt carrier group goes into battery.  The lever essentially ratchets into place with friction, providing enough resistance to being re-opened that the bolt carrier does not rebound.

http://i13.photobucket.com/albums/a254/joeplf/4%20Bullpups/DSCN0598_zpsnviefbcm.jpg

 

The FAMAS, which has a similarly insanely high bolt carrier velocity, solves the problem in a very similar way.  In this case, however, the charging handle is the anti-rebound device.  The arrangement is similar to the locking catch on an AR-15's charging handle, except that it's much more robust because the catch is responsible for arresting the rebound of the entire bolt carrier.

There are other ways still to arrest the rebound of the bolt carrier.  The Ruger MP-9 (the one designed by Uziel Gal, not the insanely over complex B&T product of the same name) is supposed to have a spring-cushioning pad at the front of the receiver which brings the bolt to a stop instead of bouncing.  The upcoming Desert Tech MDR has, by one account, "an asymmetrical [bolt carrier] face. This is accomplished with a protruding boss on one side of the carrier. As the carrier moves forward to go into battery, the asymmetrical face contacts the barrel extension first. Tolerances within the axial motion of the back end of the carrier group permit the energy to be redirected through a sideways movement. This micro-movement of the rear end of the carrier impedes the bounce and assures full function of the weapon, especially in select-fire operation."  Large caliber autocannons often have complex, articulated secondary locks that prevent bolt carrier bounce, since autocannon bolt carriers are enormous and have a great deal of residual kinetic energy.

 

So, when I read that the SIG MCX has some problems with full auto function that sound suspiciously exactly like the same problems the M16 had prior to the addition of the weighted buffer (the same weighted buffer the MCX does away with), I can only roll my eyes.  This is nothing new, and there are a half-dozen ways of fixing it.  Do your homework.

On 10/4/2020 at 9:03 PM, Must Be Spoon Fed said:

 

Around 80% casualties in war is not from direct fire, but fragments, mostly artillery. Full body armor which you can buy here would provide high levels of protection against firearms in key areas and protection against fragments in all others would drastically lower casualties rate and would make various weapons far less effective. From artillery bombardment to thermobaric weapons. In fact, most high tech body armor out there does exactly that, it looks far less than few loosely connected armored plates which we have today, but are rather full protective body suit. My opinion is validated by most cutting edge development of several nations and I was advocating for that since 2012.

 

 

 

Without any specifics, your opinion is just as valid as my own.

A modern bulletproof vest is a reliable armor protection from bullets and shell fragments. With the right choice of vest and plates for it, the vital organs of human