SpudFiles

I tried shooting 16mm marbles with an 170 cm long ABS barrel telescoped into 3/4" steel pipe... accuracy was poor... after the marbles cover the distance of about 30 m I can acctualy see them as they fly becasue they reflect the sun quite well so I know that they spin... I acctually get better results with firing bolts...

I suppose that this ABS pipe is so soft that I could try to put rifling on it with the use of something that can cut groves...
what do you think - is it possible ?
how many groves would I need ?
any idea what could i use to do it ?

It would not work on marbles, as they are harder than your barrel.
So the barrel would deform, rather than the marble.

You could do it but as necrosis said it would not work on marbles the marbles wont deform the pipe it just wont help the accuracy at all.

If you wrapped a little wadding aroung the marble, something like a paper towel or tissue paper, it might work.

if you really care about your barrel, i suggest you dont use marbles at all (unless the barrel is made out of something harder than the marble (copper, steel, etc.))

switch to something the same size (about) but made of a softer material

may i suggest:
*hot glue sticks (with wadding)
*pencils
*pvc rockets
*or the old reliable.....potato pellets

I managed to put lots of groves inside the pipe with a piece of steel that I formed into a spiral shape and attached a rope to it... the twist rate is about one twist / 15 - 20 cm... I fired 5 shots with this and it seems that it helps with accuracy but I have to test it more... All the shots were consistent but the marbles hit always a bit to the left.. I noticed that it must have been caused by the last 2 cm of the muzzle that I abused a little while trying to remove the ABS pipe from the 3/4" steel pipe....
and unfortunatelly I run out of marbles... but I'll get them on Monday

sry for double posting but does the projectile really has to be softer than the barrel..? it seems to me that it does improve accuracy...

I suppose that JSR has some knowledge about it

it doesn't have to...but it would be less wear and tear on your barrel if you did and should improve your accuracy.

According to an interview with John Bokett (not by me, I read it), if your ball (marble) makes solid contact with the lands of the rifling, it will spin enough for excellent accuracy. You have already proven this to yourself.

That being said, the surface finish on the marbles that I have seen was shall we say "less than glass smooth". As indicated, this may be hard on your barrel, testing will be the best judge of "barrel life".

Since you already have it set up, why not keep a record of shots fired and average group size. I am sure that I am not the only one here who would find such data of interest.

Good luck.

So what if it screws your barrel, getting a pvc one is a matter of 3 or 4 dollars. I'm not sure but ABS cant be much more expensive.

Projectiles have to be softer than a rifled barrel - if you had a steel projectile in a lead barrel, it would simply strip off the rifling and you'd have a smoothbore after the first shot. Note that bullets for firearms have a major diameter greater than the inside of the barrel, to allow them to "bite" into the rifling and enable the rotational movement to be transferred effectively.

If your marble is a tight fit with the lands of the rifling, then some rotation will be transferred by friction, but not at effectively if there was a soft medium fitting into the grooves.

How tight do the marbles fit into your barrel? Also, is the muzzle end of the barrel but at a perfect 90 degrees to the length of it?

@ pizlo yeah it would be easier to buy a marble PVC barrel... the problem is that there are no PVC pipes where I live and generaly they are not often used in poland... the fact that PVC is rarely used has some advantages - steel pipes are relatively cheap.. but it is still hard to find a seamless pipe in sizes smaller than 1".. not to mention that machining steel requires special tools so making rifling in steel pipe is a different story......
ofcourse bigger sizes of PVC and ABS pipes (1" and bigger) are available..but those smaller than 1" are usually very flexible... I would buy a PCV one if it offered better results than an ABS one, but I doubt it would

@JSR yeah i know that the muzzle of the barrel has great effect on accuracy... it isn't perfectly 90 deg becasue I dammaged the muzzle when I removed the ABS pipe from the 3/4" steel pipe
acctually that is the problem - I used most of marbles shooting this day (100 pcs package ) and then after I finished making the rifling I had only 5 marbles left... the target was about 40 meters from me and all those shots were consistent - the marbles struck the ground about 1.5 m to the left and a bit lower of the intended target that i was aiming at... ofcourse we could say that consistency = accuracy but 5 shots are not enought to say wheather the rifling really works well... I've noticed that the muzzle was damaged in a way that might have send projectiles more to the left but that is easy to repair ( i'll just cut those 2 cms of the barrel )

there is about 0.5 mm gap betwen marbles and the barrel... acctually it depends on the size of the marble - some of them differ a bit in their diam.

here is a pic of that twised metal thing that I pulled several times through the ABS pipe (lol it looks great as it rotates inside the barrel I'll make a video of this if my tests show that this rifling is really good and it does not wear out )
It has sharp edges on one sides and a hole to pull it.

besides having less spin, if your projectile dosem't conform to the rifling grooves you can lose some power as air will go around it.

today I tested the rifled barrel again.. and the results were not satisfactory...
i suppose it was becasue the new marbles are a little bigger (0.5 mm ) than those used before or becasue this whole idea of riffled barrel wasn't good from the very begining...

well anyway today I tried a different aproach - a hop-up
I put 15 cm long piece of electrical tape near the breech of the barrel... the tape puts spin on marbles... so far it is more promising than the rifling idea as I managed to notice that marbles flew straight and I had to aim lower than before... I managed to hit the intended target several times (an old kennel; aprox. size 1X1 meters; before you ask my dog wasn't happy about it )
I am gonna test it more soon

today I was testing my ghetto hop-up and I managed to get some accurate shots.... aiming is a bit tricky becasue I have to aim much lower than normaly but I could see that marbles were flying straight even at greater ranges so I am rather satisfied...

so.. to sum up, rifling an ABS pipe does not work well enough.... hop- up offers the best accuracy for spherical projectiles....
now I have to find some place that sells seamless stell pipes in my town...