How do I produce a "lead in" on an air rifle barrel

[Daveo]

I'm swapping the barrel on a webley Vulcan from .22 to .20
The original barrel was bent upwards when the original owner let go of it during loading.
I've got a blank, machining it to fit in the breech block isn't an issue
But creating a lead in so the pellets drop far enough into the barrel is proving difficult.
What the best way to do it?
I've experimented on a section of barrel I've cut off from the blank.
I've tried using a tapered drill bit but it left a really rough finish so I made a lap out of aluminium and tried with grinding paste but it's taking forever.
How do professionals do it?

[rancidtom]

I personally use a taper reamer, I have various reamers customised for various profiles when "chambering" a PCP barrel. Sadly all mine are .177 or .22 so I can't help with a .20 barrel.

[Rich]

Could you make yourself a tapered D bit from a piece of silver steel rod, then quench harden it, followed by a light temper? You're looking for sharpness rather than toughness.

[angrybear]

I'm swapping the barrel on a webley Vulcan from .22 to .20
The original barrel was bent upwards when the original owner let go of it during loading.
I've got a blank, machining it to fit in the breech block isn't an issue
But creating a lead in so the pellets drop far enough into the barrel is proving difficult.
What the best way to do it?
I've experimented on a section of barrel I've cut off from the blank.
I've tried using a tapered drill bit but it left a really rough finish so I made a lap out of aluminium and tried with grinding paste but it's taking forever.
How do professionals do it?

Surely the aluminium being softer than the steel of the barrel will be wearing down not the barrel
I'd go with either just the taper tip of an over size drill or a counter sink drill and then polish the finish with a hard steel ball bearing & grinding paste.

[rancidtom]

Surely the aluminium being softer than the steel of the barrel will be wearing down not the barrel
I'd go with either just the taper tip of an over size drill or a counter sink drill and then polish the finish with a hard steel ball bearing & grinding paste.

The abrasive media embeds into the soft aluminium and once embedded then cuts the harder material it is in contact with. Lead, aluminium and copper are often used as a carrier for the abrasive when honing.
EDIT:
You can even use wood to apply abrasive and the steel will still be cut.

[lensman57]

I'm swapping the barrel on a webley Vulcan from .22 to .20
The original barrel was bent upwards when the original owner let go of it during loading.
I've got a blank, machining it to fit in the breech block isn't an issue
But creating a lead in so the pellets drop far enough into the barrel is proving difficult.
What the best way to do it?
I've experimented on a section of barrel I've cut off from the blank.
I've tried using a tapered drill bit but it left a really rough finish so I made a lap out of aluminium and tried with grinding paste but it's taking forever.
How do professionals do it?

If you have an accurate lathe or a 4 jaw chuck then just cut the metal at the required angle and then hone it with a dremmel felt bit in the tool post and some soft grinding cream.

A.G

[Shed tuner]

one thing I will say - the amount of lead in is critical to power. Keep it small - too big robs a lot of power.

I posted a while back.. here:

http://www.airgunbbs.com/showthread....RWS-superdomes

[Daveo]

Thanks fellas
Taking all that's been typed on board I've managed to get the pellets to fit just below flush with the breech with a little bit of thumb pressure.
I'm happy with that, didn't want the pellet dropping halfway down the barrel
Trouble is I only have JSB pellets to try for fit
They seem to have a big skirt and be very soft I really hope they group ok now.....
I tried various things with grinding paste and a 4 degree lap but it was painfully slow going.
I found a demel grinding bit, reshaped it and used it in a drill chuck in my lathe.
I used autosol as lubricant..
It's a rough and ready way to do it and the engineers out there will be shaking their heads.
but you've got to piss with the dick you've got.

[hmangphilly]

If you have an accurate lathe or a 4 jaw chuck then just cut the metal at the required angle and then hone it with a dremmel felt bit in the tool post and some soft grinding cream.

A.G

one thing I will say - the amount of lead in is critical to power. Keep it small - too big robs a lot of power.

I posted a while back.. here:

http://www.airgunbbs.com/showthread....RWS-superdomes

what they said ^^^^^ sounds like you've got the tools no problem