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Opening chokes


polski
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Unfortunately it costs the same to bore chokes be the gun worth £1000 or £100 . Chrome chokes will cost more as they have to be bored rather than reamed so there is a time factor involved .I do think £100 per barrel is excessive and would have though between £50 and £75 for the pair .

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Its not difficult to open chokes with home equipment - an electric drill, home made mandrel, wet and dry paper and a Vernier gauge.

 

Take a piece of pipe, steel / alloy / brass, does not matter as long as rigid. About 8mm dia, but anything that will fit your drill chuck will do.

about 4" long and cut a hacksaw slot 2" down it.

 

Cut a patch of 80 grit wet and dry and put it through the slot and spin the drill against the barrel wall.

Using it wet, and measuring regularly, take off 9th for every choke increment you want.

Cy is 0.729 dia ;- 1/4 0.720 etc

 

The choked area is usually about 2" long, so make sure you are cutting back into the barrel and not just flaring the end.

 

When down to size, polish with increasingly fine grade of W&D.

 

Takes a bit of time and effort, but costs little to DIY

 

If you can, its worth patterning the gun BEFORE you mod it, as choke sizes recorded on the gun may not be what its delivering now. Find out TRUE choking before modifying, as many guns throw patterns widely different from what is recorded on the barrels.

Edited by clayman
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You cannot put metal back, so you could "over-open" against the results you want, which is why testing the choke output at stages as you let the choke out would be beneficial. Other possibility would be uneven relief, i.e. oval! Thats just a matter of ensuring you turn the barrels as you grind so pressure goes around evenly.

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If your going to do it with a drill get a big split pin pull the emery cloth in the gap and then put the leg ends in the drill and you have then got a rounded end sticking out so as not to do any harm use this method for cleaning bearing seats and the like

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Certainly, if you can beg, buy or borrow a reamer the results are quick and precise, and its the Pro way to do this.

 

U-tube

 

If you thread a barrel for M/C, or port it etc, proofing is required, but shortening barrels or reaming out no further than Cy in the choked area does not. If you have any doubt, ring the Proof House for advice.

 

Note, shortening is another way of opening up - cutting barrels back beyond the choked area gives cy and cy, and if you have an inside gauge, you can shorten just enough to remove part of the taper and thereby open up progressively as you shorten. This method may have issues with bead / rib, but is a way of salvaging barrels with choke issues, ie, turn a blown M/C into Cy and Cy for skeet etc.

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I have done a number of guns over the years for customers, always reamed out, then finished with a set of stones designed for polishing brake cylinders out, never had a problem, if you only want a fraction out, get a set of cylinder honing stones, made by sykes pickavant...

by using these self centering stones you dont risk an offset choke.

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