[HT/LT] Sawed-Off Smoothbore Longarms

[Gigermann]

As far as I can determine from the "Sawed-Off Shotguns" sidebar in HT, and the "Shortening Long Arms" sections in Gun Fu and Tactical Shooting, if you cut down the barrel length of a smoothbore (shotgun, musket, etc), it has no effect on damage or range. (TS does mention reducing damage and Acc for rifles, specifically.) This causes me to raise an eyebrow. I can't imagine that reducing the barrel length has no effect on muzzle-velocity. Or is the effect really that marginal? If true, what's the point of a long barrel on a smoothbore in the first place?

Have I missed something?

[Varyon]

Accuracy: A longer barrel forces the bullet into a straighter path, for increased precision. It also gives the shooter a better sight picture. In GURPS terms, longer barrels result in higher Acc - although with the low Acc of many smoothbores, this is arguably not as big of a deal as for rifles. At least, that's the way I feel it should work, but HT and TS have shortening the barrel only reduce Acc for rifled weapons.

Bayonet: Historically, many smoothbore longarms were designed to be used in conjunction with a bayonet, and a longer barrel gives you longer Reach. Of course, you can make up the difference, at least up to a point, with a longer bayonet.

Dodge This: Related to the bayonet bit, a longer barrel gives you more standoff range (in case the target lunges at you) if you opt to get really close to ensure you finish it off (or if keeping a prisoner). Kind of marginal, but in GURPS terms it increases Reach if using a firearm for a Telegraphic Attack.

Felt Recoil: The higher weight of the longer barrel allows the weapon to absorb more of the weapon's "kick." In GURPS terms, a longer barrel is likely to reduce MinST (unless the rounds are weak enough that weight is the limiting factor).

Intimidation: A big honkin' gun looks a lot more intimidating than a short stubby one, even if both put equal-sized holes in folk.

Legality: Because they are a bit less wieldy, and certainly harder to conceal, smoothbore longarms are likely to have a higher LC than short ones.

[evileeyore]

Originally Posted by Varyon

Of course, you can make up the difference, at least up to a point, with a longer bayonet.

Ahem. I see what you did there.

[Sam Cade]

Originally Posted by Gigermann

I can't imagine that reducing the barrel length has no effect on muzzle-velocity.

Very little. Pistol,shotgun and black powder burns fast in the first few inches of barrel.

Originally Posted by Gigermann

If true, what's the point of a long barrel on a smoothbore in the first place?

Shotguns "swing" better for wingshooting or other small targets. That is beneath significance for GURPS granularity.

[Sam Cade]

Originally Posted by Varyon

Accuracy: A longer barrel forces the bullet into a straighter path, for increased precision.

Mechanical Accuracy is in no way a function of barrel length. While increased velocity may enhance practical accuracy at range a shorter barrel will be stiffer and inherently more accurate than an otherwise dimensionally identical barrel of greater length.

[Anthony]

Originally Posted by Sam Cade

Very little. Pistol,shotgun and black powder burns fast in the first few inches of barrel.

Though most likely something like a Steyr IWS 2000 would actually see significant performance degradation from being cut short; it's not a function of it being smoothbore per se, it's a function of the ammo not being designed to make much use of a long barrel. You won't see much velocity drop if you cut down a carbine firing pistol ammo either.

[Varyon]

Originally Posted by Sam Cade

Mechanical Accuracy is in no way a function of barrel length. While increased velocity may enhance practical accuracy at range a shorter barrel will be stiffer and inherently more accurate than an otherwise dimensionally identical barrel of greater length.

I was working under the assumption that a longer barrel could serve to stabilize any sort of "wobble" the bullet might have going down the barrel, but even in that case I suppose there's no guarantee a whippet configuration wouldn't be long enough for maximum stability. For the other part of it, simply having greater separation between the front and rear sights is going to give you better accuracy, because the angles that will make them look aligned to the human eye are going to be narrower than with a shorter separation. Still, may not be enough to make a difference at GURPS levels of resolution.

[Sam Cade]

Originally Posted by Varyon

I was working under the assumption that a longer barrel could serve to stabilize any sort of "wobble" the bullet might have going down the barrel,

Once a bullet hits the rifling it is spinning, they don't slip at all going down the bore. So long as the projectile leaves with sufficient spin, it is stable until the rotation slows past a threshold. Exactly like a spinning top.

Originally Posted by Varyon

simply having greater separation between the front and rear sights is going to give you better accuracy,

That is called sight radius, and it can have huge effects on practical accuracy.
GURPS firearm supplements will touch on this.

However, many smoothbores don't have a sight radius since there is only one point of aim. A front sight bead or blade.


(For that matter neither do firearms fitted with an optic of any kind)

[Sam Cade]

Originally Posted by Anthony

Though most likely something like a Steyr IWS 2000 would actually see significant performance degradation from being cut short

Assuredly. Probably just some sort of run of the mill double base rifle powder.

Originally Posted by Anthony

You won't see much velocity drop if you cut down a carbine firing pistol ammo either.

A possible gain in velocity depending on ammunition of the barrel is much over a foot long to start with. Most commercial 9mm starts running out of pizzle around 14" since the gas stops pushing and the projectile is having to screw its way down the bore using momentum.

[evileeyore]

Originally Posted by Sam Cade

Once a bullet hits the rifling it is spinning...

Did you somehow miss the thread title?