Choking question

[charub]

This has probably been asked before, but most things end up being repeated on here. ( I'm sure we would run out of topics if we didn't repeat)

I have found myself in ownership of a rather dog rough HW35. It's going to be a project rifle. I have researched the breech leak, so think I will be doing that in due course.
As I'm only a fag paper over 5'5", the rifle is almost as tall as me in its current state. I would like to shorten the barrel, is it possible to remove the barrel from the breech and shorten from that end? If so, how do I go about it?
Alternatively, I could shorten and re crown. I have just bought a 20 tonne press for the workshop and am dying to use it. I was thinking of making a former to press a new choke into the barrel by squeezing the external diameter of the barrel a number of times whilst rotating it.
Has anybody tried this? Did it work? And would a 20 tonne press be enough?

Thanks in advance for any input.

[charub]

I'm surprised that nobody has waded in with an opinion. Is it because the idea is so absurd?

[bighit]

try the US forums http://www.network54.com/Forum/79537...+Airgun+Barrel
http://www.gatewaytoairguns.org/GTA/...topic=108629.0
I have heard of people turning a ring and heating and putting on a turned down barrel .as the ring contracts it chokes the barrel

you will just get people arguing that they are not needed on here even though barrel makers say its better to have ,one being lowther Walther

[Artfull-Bodger]

The possibility of creating a concentric choke in that manner is slim to say the least, you would be astounded how much pressure is required to compress a 16mm steel rod (barrel).

If you must shorten the barrel

First thing I would do is go to B&Q and buy one of the 4mm glass fibre/plastic rods they sell for a quid or so, then buy a small file handle whilst your there and fit the handle to the rod (not in the store obviously).

What you do then is round off the other end of the rod and use it to push pellets through the barrel slowly with your finger on the back of the file handle, what your looking for is the file handle rotating as the pellet follows the rifling, your also feeling for tight or slack spots, you will find the factory choke in the end of the barrel but you may also locate any tight spots further down, sometimes (not always) you may find a tight spot or slightly tighter section in the length where you could shorten the barrel, if you are lucky enough to do so, use the middle of the tight spot as a choke by cutting the barrel there.

[rabbitwrecker]

Don't shorten the barrel - stand in a Grobag for a week...

[Dan944]

I have actually had success in rechokeing a hw barrel that I've shortened by using x2 huge nuts which I lathed the inside diameter to 16mm or what ever the exact barrel diameter is? Then cut a 2.5 mm slot all the way through one side with a grinder.

By sliding it over the end of the cut barrel as a collet then putting the nut in a very very large heavy duty ribbon vice ( can't remember the number off hand ) then tightening the jaws until u see the gap or I used feeler gauges tighten ever so slightly. ( a large bar was used to create the tourque on the jaws but warn u now the torque was so high on the crush of the hard barrel that the bar of the vice bent)

Then time after time I would as said above push a pellet through where there was no resistance or tight spot before and then there was I then new I created a new choke.


I tested with pellets before and after and saved a few pellets to inspect the lan groove depths cut from the rifling and it was clear to see the difference before and after.

This is a mission I can tell u know and I may have been the only person to achieve this on the forum in this way as most said it can't be done I'm not sure? But I was determind to and I did but what else I can tell you is I once ultra shortened a hw 77 to a silly length of around 6" barrel and with a tune that thing was a tack driver up to 40 yards. ( that barrel had no choke left whatsoever and I sold that with a tyro stock for very good money as it was a one off and I wished I'd kept that now )

I'd suggest maybe do a pellet test before and after choping and recrowning the barrel as u may be hapoy withought a choke if as said above you don't find any tight spots ?

Good luck

Daniel

[charub]

Just read June's edition of AGW - seems that I wasn't far off with the press idea?

[Gunfun]

The other way to form a choke is to 'hand lap' one by hand lapping most of the bore but lapping the last inch of the muzzle slightly less. I'm certain that custom centre fire barrel manufactures use this method to produce a choke especially if they produce 'cut' rifling, but they are secretive about these methods.
https://kriegerbarrels.com/about

I've measured the force required to push a pellet past a choke on HW and Steyr barrels on found about 900 grams is required which seems like a lot of force to me. I'm sure hand lapping a choke into a parallel barrel bore could produce a much more precise and less restricted choke that would take less energy from the shot and produce better accuracy. Of course it just depends if you have enough tolerance to lap the bore in the first place.
There is an DOC. on the web by Charlie de Tuna/Scot Laughin on hand lapping air rifle barrels.

[buttloaves]

You could always make a collet that fits the outside of the barrel, if you press a cone over its tapered head it will squeeze the barrel, id say a better way to use the linear pushing force of a press to reduce the diameter of a cylinder compared to using it like a power hammer..
Not sure what size press you would need, i remember seeing a vid of the smooth twist barrel being twisted, it was an impressive machine, hydraulic jaws clamped the barrel forming its internal shape and the it twisted it a bit, im not sure who designed it ive read it was Ben Taylor then i think it was T D at the Fx factory who said it was designed by Fred, i think thats how i heard it, not trying to put words in your mouth Terry, please correct me if i am wrong.
My mate Bill built a 70ton press in his garage, its awsome, squash owt.

[bighit]

You could always make a collet that fits the outside of the barrel, if you press a cone over its tapered head it will squeeze the barrel, id say a better way to use the linear pushing force of a press to reduce the diameter of a cylinder compared to using it like a power hammer..
Not sure what size press you would need, i remember seeing a vid of the smooth twist barrel being twisted, it was an impressive machine, hydraulic jaws clamped the barrel forming its internal shape and the it twisted it a bit, im not sure who designed it ive read it was Ben Taylor then i think it was T D at the Fx factory who said it was designed by Fred, i think thats how i heard it, not trying to put words in your mouth Terry, please correct me if i am wrong.
My mate Bill built a 70ton press in his garage, its awsome, squash owt.

I'm pretty sure it's a bought in swaging machine with a custom dies
http://www.network54.com/Forum/79537...are+interested

Swaging machine does this. https://youtu.be/uUQ0HrCJT_k they just swage the end using their custom die

[buttloaves]

I'm pretty sure it's a bought in swaging machine with a custom dies
http://www.network54.com/Forum/79537...are+interested

Swaging machine does this. https://youtu.be/uUQ0HrCJT_k they just swage the end using their custom die

So it would be the die that is special?

[bighit]

So it would be the die that is special?

I would think so in the case of the smooth twist barrels.