How to choke the BBL?

[DMikeM]

Could this be used to apply a choke? http://www.grainger.com/Grainger/DAYTON-Shaft-Collar-1L699?Pid=search

Protect the BBL with some thin leather crank it down and repeat every 45°
What other methods are used to apply a choke?

[tkerrigan]

Not enough squeeze to do anything, have a sleeve made of steel about .0015 interference fit for the end of the barrel. Start out with about 3/16" wall thickness. Chill the barrel with dry ice and heat the sleeve to about 400° F., then install quickly.  The shrinkage of the sleeve should do what you want. You may have to experiment with different thicknesses of sleeve walls and interference.  If stainless expands and contracts similar to steel, you might be able to use it. Then it could be decorative also.  If the sleeve exerts too much squeeze and the choke is too small, just cut a slit lengthwise and it should come off with a little heat.  Your mileage may vary. 
                                                                                                Tom                                       

[Rescue912]

Threading the end (like for an LDC) can give a bit depending on the interference with the die. If I want more then I use a resistive soldering/brazing iron to heat the end of the barrel and then let it cool slowly. Burying the end in sand slows the cooling process down, never quench though.

Nothing too radical with the heat either, 350 degrees was enough to get my .25 Falcon Hunter to pucker about 0.0007" (seven ten thousandths).

Your mileage may vary, don't practice on anything nice. Took me a few times to get it right !

[DMikeM]

So just heating the bbl end can cause it to shrink? I understand freezing it causes it to shrink as well.