Shotgun / Rifles

[Zenbon]

And there I was flaunting my half baked knowledge on firearms. I had put in Ballistics as one of my fields of interest. The interviewer obviously had never seen this on a resume of a IT guy before, so he proceeded to ask on the details. I held my own for a while, then almost flopped on a basic question. He asked me what was the difference between a shot gun and a rifle. I chucked to myself at this 'easy' question and proceeded to explain to him about the rifling in the barrel, accuracy, range, bullet structure etc. It was the next question that caught me, he asked "Wouldn't the bullet have a greater velocity, speed on a shotgun type of barrel rather than a rifle barrel?" Though I managed to convince him that the rifling lent the pellet/bullet a rotational motion and this along with the centrifugal force generated would easily enable the pellet to overcome the wind resistance.
While I was doing this 'answering part' I had a question myself that I put forth to you guys.

"Wouldn't the pellet have to overcome the friction in a rifle barrel? Then how does it have a greater velocity than a shotgun?"
I apologise if I sound so ignorant.


PS: Another question I was able to answer easily was the difference between a shotgun and handgun!
BTW , I cleared the interview.

[mundaire]

What you should be thinking in terms of is "muzzle energy" and not simply muzzle velocity.

A typical factory loading for a 12ga (2.75") shotshell loaded with a 1.25 oz slug (~ 547 grains) would produce around 2806 foot pounds of energy at the muzzle.

Compared to that a 7.92mm Mauser loaded with a 150 grain projectile would produce around 2100 foot pounds of energy at the muzzle and a .30-06 loaded with a 180 grain projectile would produce about 2033 foot pounds.

As you can see the weight of the projectile (in the case of a slug) or projectiles (in the case you are firing bird/ buck shot) far exceeds the typical bullet weights of most rifle loadings (not counting the monster rounds).

More projectile weight = lower muzzle velocity ,ceteris paribus

Which is why I mentioned the need to examine the energy figures and not simply the velocity numbers...

Higher velocities (lighter bullets), their different shape and the spin produced by rifled barrels means that rifle bullets travel further and group better than shotgun slugs.

Cheers!
Abhijeet

[Zenbon]

Higher velocities (lighter bullets), their different shape and the spin produced by rifled barrels means that rifle bullets travel further and group better than shotgun slugs.

Cheers!
Abhijeet

Any any other factors to be considered ?
I remember seeing a program on Sniper rifles, even Earth's rotation was taken into account!

Do rifle bullets also have the same structure and firing method as a shotshell? Like a firing cap, gunpowder and lead slug ?

[TwoRivers]

Abhijeet:  The 7.92mm (8x57S) Mauser gave 2825 fps/2730 ft.lb. with a 154 grain bullet, the .30-06 is rated at a nominal 2700 fps/2913 ft.lb. with the 180 grain bullet. And both would be far ahead of the slug at hundred yards. Cheers.

[TwoRivers]

Zenbon: By operating at much higher pressure, four to five times higher; and having a much greater propellant-to-projectile weight ratio. True, there is less friction in a smooth bore barrel, compared to a rifled barrel, making higher velocity possible. That's why modern tank cannon are smooth-bored, with fin-stabilized sabotted projectiles. Cheers.

[msandhu]

aha.. now i know why the tank guns can be smooth bore..i was always wondering about this.. thanks for this info tworivers

Cheers
Mandeep

[Risala]

The shift in MBT's to 120/125mm smooth bores was primarily to combat modern armour llike Chobam,cause HEAT,HESH & APDS ammo wouldnt get the job done with the 105 mm rifled guns.
Since the size of the projectiles has increased,in the case of rifled guns the length to dia ratio of the projectile would govern the restrictions imposed on it,and beyond a certain stage the they would not be as effective.

This resulted in the development of the APFSDS rounds (Armour Piercing Fin Stabilised
Discarding Sabot),where the spin to the projectile is imparted by the fins & the sabot
discards itself on leaving the barrel.
These are extremely long projectiles,just to give you an example a 125 mm APFSDS round
that is fired from a T -72 the actual penetrator is approx 18" long and approx 2 " thick.
Most penetrators today are typically made from Depleted Uranium,will get the job done .