m16和sa-80的槍口初速一問

sa-80的槍管比m16長....但係點解m16的槍口初速比sa-80大~??

Well,the two answer above both did not mention why the game are the same and the bullet are the same but the Muzzle velocity is different.

Let me tell you this, cos SA80 (L85A1) is a bullpup, where the Magazine Clip were Behind the trigger, and the M16 were a normal design the Mag is In front of the trigger.

As the longer the barrel, the Bullet will have more "Spin" (as barrel is rifled, Kinetic Energy is used to spin the bullet), so the long the barrel, the longer the spin, thus the more energy used on spinning the bullet, Which leave less energy to allow the bullet to travel in the horizontal, when some of it werededicate to spinning the bullet...

So the speed is slightly faster in the m16.

It is not very hard to understand...

槍口初速大d係唔係=打遠d同埋準d??

Basically, the longer the barrel, the shorter it can go but the more accuracy, up to the satruation point when the bullet chemical all burn out but the bullet still remain in the barrel.

The reason is simple physics.

When burning chemical in gun powder Energy is produced, when passing thru the barrel, the rifled barrel will spin the bullet while IF THE CHEMICAL HAS NOT COMPLETELY BURNOUT, the energy will still supply by the pressure from burning the chemical so the speed of the bullet unchange.

However, the longer the barrel, themore spin (as i explained before) when when the pressure is gone (ie Chemical burnout) the speed will need to decrease and slow the bullet down in order to spin.

Until the point when the bullet leave the muzzle, the bullet will spin at a rate,let's say 800 rpm. The rpm will keep dropping but every spin used energy, and a slower muzzle weapon will give a smaller RPM thus less KE loss, so a longer barrel gun will have a lower range than a shorter barrelgun.

AS for how rifling help accuracy, the first one already explain it was the gyroscopic effect (Which spinning the bullet allows stabilised trijectory of a bullet) i will not explain further

兩把槍唔係一樣用5,56mm NATO個咩??sa80用唔到M855子彈個咩??

看一看它們標示的數據:
SA80: 槍管長518mm, 初速940m/s, 動能1767J, 使用M193 子彈.
M193子彈, 彈頭重 3.63g, 膛壓52000psi, 理論初速997m/s

M16A4: 槍管長510mm, 初速945m/s, 動能1765J, 使用M855 彈彈.
M855子彈, 彈頭重 4.02g, 膛壓55000psi, 理論初速922m/s

根據以上資料可以看出, 使用不同子彈, 會有不同結果. SA80 槍管長過M16A4 8mm. 但初速又細了一點, 彈頭輕了一點但又不能增大初速. 膛壓少一點但理論初速又大一點..... 可能同槍管設計, 膛線設計不用有關.

You have to also consider the diameter, material used, firing mechanism & breech design of the barrel & rifle.

Right, muzzle velocity effect the range, but NOT the accuracy.

Accuracy of any firearm come from the barrel rifling ratio. Quote from Wikipedia, "Rifling is the process of making spiral grooves in the barrel of a gun or firearm, which imparts a spin to a projectile around its long axis. This spin serves to gyroscopically stabilize the projectile, improving its aerodynamic stability and accuracy."

A chromed barrel will also increase the accuracy and functionality of the gun.

2010-06-17 15:01:27 補充：
So, Dick, you are right about that 膛線設計 is not related to the muzzle velocity of a giving gun.


But it DOES affect the accuracy of the gun.

2010-06-17 15:11:07 補充：
And, Dick, when you compare, U have to compare 2 guns with the same bullet. Otherwise, the number are meaningless with no point of reference.
When comparing 2 guns with the SAME brand, SAME type, SAME weight of ammunition and SHOOTING at the same altitude; U have a true comparison of 2 weapons