boring a long hole?

[BrokenBiker]

how would one go about drilling then reaming a hole down the centre of a piece of bar stock 410mm long.

the bar would be chucked in a lathe as this is all I have that will hold a length that long.

I have a 13mm drill chuck on an MT2 arbor in the tail stock but am struggling to think of a way to drill to that depth.

finished hole dia will be 7.62mm and reaming is essential after drilling. plan at first was to drill in stages to 7.5 then ream to 7.62mm

 

[Robotstar5]

How are you going to cut the rifling?

 

[BrokenBiker]

how do you know its a rifle barrel?

rifling will be cut by a friend who has some sort of jig setup for doing this

 

[500e]

Most whippets are smooth bore

 

[BrokenBiker]

this is going to be for a target air rifle, sort of home build but using the internals from a BSA ultra SE

 

[Jim_gsxr1000]

Making a barrel from scratch ?

 

[MattF]

With difficulty is the simple answer, especially at that diameter of hole. You'll have to feed that with a baby touch to prevent the risk of it wandering off centre, I'd guess. You want to be using a MT drill bit rather than chuck mounted one too. Chances of the bit being held dead straight in a chuck are slim.

Have you asked your friend with the rifling jig how he drills the bore hole?

 

[BrokenBiker]

I have no problem with going slow, it takes as long as it takes. im just wondering how I would get to the depth. the longest drill I have is 100mm long and I cant think of any way to 'extend' it

there must be away because I have seen rifles that have been re-bored from .22 to .35

he doesn't do the boring, only just made the rifling jig and tested it on a few bits of pipe. all went well so now we want to try it on a proper sized barrel but we cant find one that isn't rifled

 

[Keith 66]

7.62 target air rifle, that will need to be an fac job for sure.
Best book i have found on the subject is Barrels and Actions by Harold Hoffman
it was published in 1991 by H&P publishing San Angelo Texas.
It was written by a Gunsmith who wrote in a simple terse common sense style.
It has everything on boring barrels and button rifling them you could ever need to know. He used a D bit gun drill with hollow v sectioned tube, cutting oil pumped through the drill at over 500psi with the lathe running at a very high speed, a 30 cal barrel woud be bored through in 5 minutes flat.

 

[MattF]

I have no problem with going slow, it takes as long as it takes. im just wondering how I would get to the depth. the longest drill I have is 100mm long and I cant think of any way to 'extend' it

You don't extend a bit. You make one specific to the job. An old style drill bit of a long length of rod with a spade bit shape cutting tip on it is likely going to be the best form to use and make for a hole of that length.

 

[BrokenBiker]

cheers keith, will have a look for the book, plan on making a few of these barrels if all goes well.

the rifle itself wont be FAC, will be around 11ft/lbs, no need for long range or power, just accuracy at 25 yards

the barrels shouldn't need to be listed on FAC either as they are not chambered to take any live rounds although I am waiting to hear back about this from met police

 

[BrokenBiker]

You don't extend a bit. You make one specific to the job. An old style drill bit of a long length of rod with a spade bit shape cutting tip on it is likely going to be the best form to use and make for a hole of that length.

I was thinking along the lines of boring into the ground, been watching a company that is removing the oil from under the factory I work in, they just attach the cutting end into extension bars that are 10 foot long each

though a similar principle may apply here, but sadly its not that simple

 

[wyn]

On T W Chambers website you can buy up to .25 Lothar Walther barrels with no problem but if you want a .30 barrel they want proof of FAC.

I supose they just assume it will be for a FAC rifle.

 

[BrokenBiker]

they usually are but you can now buy .30 in under FAC air rifle, but there are only a handful out there I think, possibly all modified to sit under 12ft/lb this is why I checked with met police though as it may be a calibre related licensing.

I don't really want a load of barrels on my FAC, as they have to be removed again once the rifle is assembled and proved to be below FAC

 

[octo0072000]

you may find police won't like the idea as 7.62 barrel can be converted to live ammo they banned was it brococks .22 air pistols (looed like a .38 smith&wesson pistol
the barrel was drilled out to use .38 calibre rounds by certain people
see pictures

https://www.google.co.uk/search?q=b...8K6Wu7Aasn4CwAw&ved=0CD8QsAQ&biw=1152&bih=625

 

[BrokenBiker]

you can buy .30 air rifles though, and to be fair, pretty much any barrel can be converted to take live ammo, a .17hmr bullet would go down my .177 air rifle barrel with no issue, and a .22lr or .22 hornet would go down my .22 air rifles. a .223 will go down the one of my air rifle barrels as well

 

[octo0072000]

you can buy .30 air rifles though, and to be fair, pretty much any barrel can be converted to take live ammo, a .17hmr bullet would go down my .177 air rifle barrel with no issue, and a .22lr or .22 hornet would go down my .22 air rifles. a .223 will go down the one of my air rifle barrels as well

problem is it's just the way the law looks at it though that's why i no longer have a FAC or shotgun certificate now
just have sub 12lbs foot now

 

[wyn]

You could try a long masonary drill bit with a bit of work on the sharp end and turn down the flutes you might get an 8mmx 450mm to work.

 

[scott0031]

In a nut shell you pretty much wont be able to do as you want. The process used is called 'gun drilling' funnily enough. You tube the term for more information.

There are specific machines designed for gun drilling or gun drills can be used on slightly more conventional machines like horizontal machining centers. The dark art of gun drills is in the tip geometry, The shanks are totally soft and highly ductile to absorb resonance. You can bend the shanks in half by hand on those gun drills with smaller diameters. Gun drills are also used with very high pressure through coolant systems to blast the chips away from memory this can be in the region of 2000 psi to allow accurate machining with a very high surface tolerance which are not achievable by traditional twist drills.


As mentioned you can buy barrels made by gun drilling company's, this is the route everyone ends up going down as its the only cost effective way of getting the result you want.



Kind regards,



Scott

 

[brightspark]

why dont u just buy a decent gun cheap and use its barrel if u want a modified gun