scratch rifling

[Biker_Bob]

yeah, you need something that will uniformly spin and feed at the same time, as stated above.

a square section (say 1/4") length of steel, heated and twisted (one turn in 16" is common), might form a suitable pattern ? feed it though a square hole, and the rod will twist as it feeds. youd obviously need to attach a sub .177 sized steel rod to the end of it, and the end of that would need your "scratch filing mandrel" or button, or whatever it's called.

Just thinking aloud... something like a giant yankee screwdriver

and yes, definitely pull, not push...

This is genius!

I was trying to think of how to do this with a lathe, but lathes generally don't have the gearing to cut threads as coarse as you need to make rifling.

[isobar]

Thanks.
I suppose I was just trying to think of a method that could be done by "Ghetto engineering" & without it becoming elaborate or expensive.

It occurred to me that using something like this method shouldn't take much force, and even if it was difficult to do by hand it might be possible to modify something such as a silicone sealant gun to apply the moving force.
On the plus side, the "donor" rifled barrel could be of any calibre as it's sole purpose would be to act as a template that would turn the emery carrier at an even rate. Of course, a jig of some kind to keep the bores of both barrels concentric with each other would be needed, and the rod connecting both the "lead plug" (or whatever) and the emery carrier would have to be the right length to do the job.

i begin to understand this idea now,thankyou

[isobar]

yeah, you need something that will uniformly spin and feed at the same time, as stated above.

a square section (say 1/4") length of steel, heated and twisted (one turn in 16" is common), might form a suitable pattern ? feed it though a square hole, and the rod will twist as it feeds. youd obviously need to attach a sub .177 sized steel rod to the end of it, and the end of that would need your "scratch filing mandrel" or button, or whatever it's called.

Just thinking aloud... something like a giant yankee screwdriver

and yes, definitely pull, not push...

i couldn't get my head round this idea but am beginning to understand where you are coming from.i think you are suggesting that if a twisted rod is pulled through a suitably sized square it will twist evenly and possibly faithfully and if attached to that twisted rod was another rod carrying the scratching devise it would produce the rifling?

[evert]

If you twist a rod to make your "twist guide" (worm?) how du you ensure the twist is even down the entire rod?

[Shed tuner]

i couldn't get my head round this idea but am beginning to understand where you are coming from.i think you are suggesting that if a twisted rod is pulled through a suitably sized square it will twist evenly and possibly faithfully and if attached to that twisted rod was another rod carrying the scratching devise it would produce the rifling?

yup....

[Shed tuner]

If you twist a rod to make your "twist guide" (worm?) how du you ensure the twist is even down the entire rod?

yup... but here's another question... how consistent does it need to be ? obviously not miles out, but is it really that critical if it's one turn in 15 for the first half and say one in 16 for the second half ? I have no idea !

[greenwayjames]

Crosman used the same principle on some of their repeating rifles and pistols to operate a loading gate from magazine to breech position. 400 rifles, 600 pistols and previous.
Scratch rifling is just that. No more than that produced by very coarse emery cloth or linishing belt. It can produce good accuracy which was one of the questions originally put

[Adam77K]

yup... but here's another question... how consistent does it need to be ? obviously not miles out, but is it really that critical if it's one turn in 15 for the first half and say one in 16 for the second half ? I have no idea !

I don't think it matters that much. Progressive twist rifling has been done for years, as has just rifling the last few inches. I guess it's not optimal to have the twist nearer the muzzle slower than nearer the breech as you're just wasting energy imparting a faster spin then slowing it down.

[isobar]

At this moment I'm not exactly sure how to do it, but it occurs to me that it may be possible to use another (rifled) barrel, along with something that will engage with its rifling and a sub-calibre rod to connect with whatever carries the emery if the barrels are placed end to end, then push this assembly down the rifled barrel toward the smooth bored barrel so that it imparts a "spin".
Does this make any sense to you or am I talking through my hat ?

this is the idea i'm inclined to pursue,i have some tubing to practice on and some slugs for a .22 barrel.not quite sure of the set up yet but will do plenty of dummy runs even on the practice tubing.if the .22 slugs haven't enough mass to follow the rifling i'm sure i could melt some lead to make a bigger plug.just a thought!would it be an idea to cast a "plug" in the rifled barrel?who knows if i can get it to work?but it seems to be within my capability and understanding.
please keep the ideas coming,i'm quite enjoying the mental exercise.

[isobar]

yup... but here's another question... how consistent does it need to be ? obviously not miles out, but is it really that critical if it's one turn in 15 for the first half and say one in 16 for the second half ? I have no idea !

it's an ingenious idea and i think i could possibly do this in the shed.i would have to find some bits and pieces.i am very grateful for these suggestions,i would never have come up with this sort of logic.
you're all a load of engineers aren't you?

[keith66]

Im curious how much spin you would really need to stabilise an air rifle pellet, Muzzleloaders shooting ball often had one turn in 6ft, a fast twist was 1 in 48". If you are scratch rifling it would make sense to use the minimum twist that would stabilise the pellet, any more & the risk of it skipping the rifling grows.

[isobar]

Im curious how much spin you would really need to stabilise an air rifle pellet, Muzzleloaders shooting ball often had one turn in 6ft, a fast twist was 1 in 48". If you are scratch rifling it would make sense to use the minimum twist that would stabilise the pellet, any more & the risk of it skipping the rifling grows.

quite possible i suppose,difficult to assess the risk.i was hoping the relatively low velocity would work in favour of a standard twist rate.i will before i do anything attach a rifled barrel from another rifle to see if it shoots more accurately,if not,project over.

[isobar]

Spinning a drill will just cause rings,you need a slow helix 1 in 16" is common ,you could do it by hand pushing a glass rod
with emery glued to it along the barrel whilst feeding the barrel with the other hand and rotating it,but I wouldn't bother I
would recrown the barrel and find a suitable pellet

silly me,this was the answer,hobby pellets came to the rescue again.the little rifle is shooting well with these without the ridiculous fliers.

some great ideas on this thread from a while a ago.