Pitted Bore Vs. Smooth

[cloud8a]

A thought just crossed my mind. If a rifled bore is pitted and loses accuracy is it still more accurate than a smoothbore?

[Bill Akins]

Cloud 8a wrote:
A thought just crossed my mind. If a rifled bore is pitted and loses accuracy is it still more accurate than a smoothbore?

The key phrase in your above sentence is "loses accuracy". If the bore is so badly eroded that it significantly loses accuracy and the rifling grooves do not engage the projectile at all and imparts no spin, then it may be no more accurate than a smoothbore. However; the accuracy loss would depend on the degree of rifling lands and grooves erosion. Light pitting would not do that. In fact lead (if using lead projectiles) will often fill light pitting as the bullet travels down the barrel so that the pits are almost filled....(and if the lead is not removed from the barrel with a lead remover). In your above scenario the rifling would have to be so badly eroded that it imparted no spin on the projectile and gave the same effect as a smoothbore. If however the rifling erosion was just enough to slightly affect accuracy without totally losing all accuracy, it would still be better than a smoothbore because any gyroscopic spin imparted from the rifling onto the projectile to stabilize it in flight is better than no spin at all. So your above question would depend solely on the degree of erosion of the rifling. Generally speaking my opinion is that if the rifling spins the projectile at all, it will be more accurate than a smoothbore with no gyroscopic projectile spin at all.


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[cloud8a]

I have heard alot of folks suggest that if a person has a badly pitted bore they could have it turned into a smoothbore. Are there other problems that come with a bore pitted bad enough to effect accuracy? In other words are there other reasons to smooth out a pitted bore other than possible loss of accuracy, like safety or further damage.

This scenario assumes that once one has a badly pitted bore they take constant care of it.

Is there a point at which pitting in a rifled barrel could cause it to be less accurate than a smoothbore?

I guess what I am trying to get at here is that it sounds like one should not smooth out their bore because of pitting, because its always better to have some rifling, right?

I am sure there are factors I am not considering here. that is why I posted this so you guys could educate me on this thought of mine.

[arcticap]

A smooth rifle can shoot just as accurately as a rifle can at 50 yards. So if the bore is pitted then the chances are that the rifle will no longer be able to match the performance of a smooth rifle. At a much longer distance maybe the rifle would out perform the smoothie, but that won't be saying much for the overall accuracy of the rifle though.

Originally Posted by cloud8a

Are there other problems that come with a bore pitted bad enough to effect accuracy?

Yes, the pitting rapidly accumulates fouling so the accuracy degrades rapidly as more shots are fired.
The pitting makes it very difficult to swab the bore clean because the pits collect so much fouling that it really cakes up the bore.
The bore could be swabbed 10 times and it still won't be clean.

Originally Posted by cloud8a

I guess what I am trying to get at here is that it sounds like one should not smooth out their bore because of pitting, because its always better to have some rifling, right?

False. It best to test fire the gun for accuracy at a moderate range like 50 yards. Experiment working up loads to see if all of the shots will hit a paper plate at that range. If it won't hit the plate most of the time then consider lapping the bore to smooth out the pits to see if that improves its performance. If it doesn't, then keep lapping until the pits are mostly gone or it's decided to turn it into a smoothie.
A smooth rifle can fire 1 -2 inch groups at 50 yards if it's loaded properly with a tight fitting patched ball.
But if a gun can keep its shots on a paper plate then that's good enough for recreational plinking and hunting unless better performace is desired.

[mykeal]

+1 arcticap

[cloud8a]

Very good. When you say lapping the bore, do you mean with a grinding compound like you have mentioned to me before?

So a badly pitted bore can be less accurate than a smooth under 50 yards but then become more accurate beyond that?

[arcticap]

Yes, I imagine so. But that's just my guess.
I wasn't thinking about a badly pitted bore as much as one improved by lapping or a bore that was only moderately pitted to begin with.
The severity of the pitting and the degree of bore roughness could make a considerable difference.
Worn out rifling can lose its accuracy too, but that's also a matter of degree.

[Model-P]

So a badly pitted bore can be less accurate than a smooth under 50 yards but then become more accurate beyond that?

No. Once the shots have spread, they aren't going to magically come back to center. They will keep spreading. A gun that is less accurate than another at 50 yards isn't going to all of a sudden outshoot the other at 100 yards, ever (unless you add wind to the equation).

By the way, you didn't mention what type of gun. IIRC, a smoothbore center fire handgun is considered an NFA weapon and illegal to own without the proper license. At what exact point does a rifled barrel legally become a smooth bore due to wear? I dunno. Can't explain stupid laws.

[arcticap]

By the way, you didn't mention what type of gun.

The discussion is about muzzle loading long guns, a rifle with a pitted bore.

A gun that is less accurate than another at 50 yards isn't going to all of a sudden outshoot the other at 100 yards, ever (unless you add wind to the equation).

Round balls fired from some smoothbores tend to knuckle beyond the effective range of the barrel.
That's why even poor quality, pitted rifling may be able to outshoot a smoothbore at longer range but not at 50 yards.
The effective smoothbore range is different for every barrel and load, mostly based on qualitative differences of the barrels.
The wind has nothing to do with the ball knuckling, but the caliber and/or velocity of the ball might. Once the ball starts to knuckle, I think that it can go helter skelter. Especially if it's a choked shotgun barrel. I can only say that one of mine shoots pretty good out to a certain distance and then the ball just goes haywire. It's a 28 ga. with a modified choke.

[Model-P]

O.K. I see what you're saying. Interesting.

[Swede68]

Perhaps slightly besides the topic, but it may still be of interest to the original poster.
I´ve been shooting original/antique blackpowder guns for over 20 years (I shoot modern guns too but it isn´t half as fun!). My favourite type of antique gun to shoot is a percussion revolver, but I´ve shot cap and ball rifles and carbines too. When it comes to rifled barrels, in my experience, something like a tiny nick at the muzzle can hurt precision a lot more than a badly pitted bore.

Bores can sometimes look awful, yet still produce extremely good accuracy. When looking for a cap and ball revolver to shoot (usually a Colt), I watch out for deep pits that cut through and make a break in the rifling, that´s allways a bad thing. A barrel that is otherwise in mint condition with a mirror like finish and razorsharp lands and grooves but with a single pit that puts a break in the rifling is generally worse for precision than a bore which is lightly but evenly pitted all through.

Last thing regarding rifled barrels..., a bore with quite serious rustpits but with sharp edges of the lands and grooves is often a lot more precise than a bore with a mirror finish (one that has obviously never been stored dirty) but which has thin rifling and rounded off edges in the lands and grooves (from simple wear) is.

To sum it up, a bore can look godawful overall yet be capable of outstanding precision, and it can look quite allright except for some little thing and be useless for precision work.

And to answer the original question (which has allready been done), a good smoothbore will outperform a bad rifled barrel, no doubt about that. Question is "what makes a bad bore?", because it isn´t down to apearance only!

Regards!
Anders Olsson