Smoothbore Barrels

[LMNOP]

I have recently caught the slug bug and have noticed that if I smooth out the rifling and remove it entirely via abrasive polishing that not only do the slugs travel faster but it seems POI is much more consistent. My theory is that due to low muzzle velocity using slugs that the twist rate is not enough to spin stabilize the slug. Is anyone else using slugs in a smooth bore setup?

 

[MEC17670]

What velocity are you talking and what gun are you shooting?
Without some rifling , I can't see how smooth bore without a choke will be very accurate at extended ranges.
There's been a tremendous amount of research on stabilizing slugs to optimize the accuracy of slugs, check some of it out.

 

[LMNOP]

450 FPS out a P-Rod

 

[Pale_Rider]

No wonder you were having trouble shooting slugs.. you’re shooting them at low speed and out of a choked barrel. Sure some folks can get decent accuracy out of choked barrels but they’re shooting them much faster than 450 fps. I’m guessing that you’re shooting at a short distance. Try shooting longer distance and you’ll find out why you need rifling.

 

[Peashooter]

You need to spin a slug to stabilize it as it have no stabilizing feature, a pellet have its skirt to do that job so essentially a pellet would not need rifling.
The old ST barrels from FX are smoother bord all the way aside for the last couple of inches, so things shot thru those still get a spin before they leave the barrel.

I generally shoot my .177 slugs ( mostly 13 grain ) at over 900 FPS, this of course in a rifled barrel ( choked ) but i have been as high as 1030 FPS.
I am looking to get into none choked barrels in the .177 caliber, which are not super easy these days unless you get a longer choked barrel and chop a few inched off the end to remove the choke.
Larger calibers you have more choice both in choke / no choke and also twist rates on the barrel.
ATM all larger caliber seem to have a faster twist rate if the barrel are for slugs, but in .177 caliber that do not seem to apply so standard and slug barrels are same twist rate,,,, which i find suspect.

 

[Ballisticboy]

Slugs need spin to stabilize, as they are aerodynamically unstable. For the same twist rate, slugs get less stable as speeds are increased due to increasing aerodynamic instability, so the faster the slug is fired the faster the minimum twist rate required. There is no reason slugs should not be stable at 450 ft/sec, I have tested spin stabilized projectiles at less than 300 ft/sec which fly quite happily. The important factor for spin stability, apart from the degree of aerodynamic instability, is the ratio between the forward velocity and the spin rate, not just the spin rate alone.

Even after polishing, it is possible that there is some spin being given to the slugs as they pass down the barrel. Years ago, so-called scratch rifling was looked at for airguns with some success. A small amount of spin with the low speed may keep the slug close to stable over short ranges. As said previously, it is unlikely to stay for longer ranges.

 

[LMNOP]

Thanks for this — has anyone determined the advantages of clockwise versus counterclockwise spin stabilization?

 

[Bigragu]

@LMNOP-
You’ve been a member on here for awhile, as I’ve read some of your replies. For sure you must have read some slug topics, topics like the Panthera and all the crazy fast speeds people are shooting slugs at.

I’ve also never ever have read on anyone attempting to shoot a slug out of a prod as that’s not what a prod was designed or meant for. Most, not all, but most, know that Benjamin prods are one of those awesome mag fed pistols that do well shouting 22 cal pellets at around the 650-700 FPS range.

So, I have to ask- are you pulling our legs by asking about lapping off rifling out of a prod to shoot slugs out of, and continuing on and asking about twist rate?

Don’t mean to be rude, as like I mentioned I’ve seen your replies many times before and it doesn’t seem like you would ask such a question