Barrel choke

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xpfuzz

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As I have read and found,by slugging a barrel you can find where to cut the barrel for the crown,,but if a person was to,,,or had to make the barrel shorter,thus doing away with the choke,,could a person put the choke back into the barrel by making a clamp collar to attach to the end of the barrel and thus by tightening the screws on the collar,,make the choke reappear again in the barrel...Just a crazy thought..:p any thoughts????
 
I tried this and all it did was make my bbl shoot eratic. I think the choke needs to be somewhat gradual. My collar was only about 1/2".
 
ok,what if a person made it about 2 inches long with lets say 4 screws,,and tightened each one a little more,thus/maybe making it tapered???
 
G'day

I read an article recently in a magazine, where the author put a collar on the muzzle to achieve what your talking about.
It was done to a rifle that came from the factory with a bad barrel ( oversize bore and an even bigger swelling of the bore at the muzzle).
This was not a benchrest gun but a bolt action sporting rimfire.
He turned down the muzzle end of the barrel in a lathe ,and then bored a collar that was undersized.He attached the collar with a shrink fit (heated it so that it would expand , pressed it on and then let it cool and shrink).
It seemed to work if you believe the article ( improving the accuracy remarkably).
I don't think I would try it with an expensive barrel ,but a very interesting experiment.

Thankyou for your time

harro
 
Achieving the proper choke at the muzzle is easier said than done. Unless you have access to a bore air gauge you are going to have to just guess at, or go by feel, as to what you are doing. Most gunsmiths who lap barrels to achieve a choke go by feel. Once you learn this technique you can do a pretty good job.

After you decide where a choke exists in your present barrel and then cut the barrel off at that point, you will enlarge the choke. Whether or not you will remove the choke entirely can only be determined by measuring - with gauge or by feel.

Now as to use of a collar to shrink the barrel; this can easily be done. Barrels can be choked by reducing bore diameter, groove diameter, or both. A barrel might have a choke machined or lapped in it by any of these three. A collar will only reduce both bore and groove diameter.

To get a choke that extends completely out to muzzle it's necessary that collar hangs out over the muzzle. If this is not done the bore will have a slight bell shape instead of a constant taper. (This is advantage of angled or counter bored crown, not often mentioned)

Length of collar is not something I know how to calculate. You probably just have to decide what looks best to you and go with this. Just decide how long you want the choke to be and make your collar to this length.

All diameters of barrel and collar plus the amount of interference can be used to calculate how much the bore will be decreased by adding a collar. Again you will have to some how decide how much choke you want to try and achieve. I could show you how to calculate this but since you probably aren't going to be able to make the measurements to get a starting point I have a feeling it might be best to do the whole thing by "seat-of-pants". If I were doing it I'd probably make a sleeve about an inch or so, long, 1/8 radial thickness, hanging over the muzzle 3/16 inch, with .002/.003 interference. Remember this is hardly more than a guess, so take it from there
 
I can calculate the choke pretty closely mathematically but it is really much more complicated than that. Barrels are not static - when they are shot they heat up. The stress induced by the turning process, combined with the (not so) static stress from the shrink fit sleeve would lead to unpredictable changes in the dimensions of the barrel at the muzzle - not good! At the very least such a barrel would require a lot of foulers to simply warm it up. If I were experimenting with a sleeve I would avoid turning the muzzle at all costs - just make a large enough sleeve to fit over the existing diameter. Additionally, I would minimize the dimensional difference of the shrink fit - also to avoid unnecessary stress.

I'm really surprised someone hasn't tried something like a collet that fits over the muzzle. Then you could tweak the torque on the collet to adjust choke. I haven't run the numbers to see if a collet could exert enough force to change bore dimensions significantly, but its an interesting idea...
 
One way to look at it

If it's already been tried (probably has), and remains largely unknown, it didn't work very well.
 
Barrel Choke

Just for a fun "What if" could the muzzel be sandwiched between 2 blocks of dry ice and allowed to chill. Then clamp with a radiator hose clamp before coming back to room temp?
 
sleeves, collets, clamps, bands....

This is called a compound cylinder out there in that world of science and engineering. It is used so much and there is so much known about it the I have to laugh at Wilbur's use of terms like "largely unknown" or msnations's "unpredictable". I'll go so far as to say anything you want to do to the muzzle, that is any change you want to make in it's diameter, I can do in a perfectly stable, predictable manner by shrinking a band on it's outside diameter. I can't say what the effect will be on accuracy, but if you know what you want to do to the bore, it can be done with an interference fit collar.

To saikatana...Cooling the inner barrel is same as heating the outer band or clamp. When all is returned to room temperature you are left with an outer band shrunk on the inner. Your use of dry ice (or liquid nitrogen) to cool the inner barrel is used all the time out there in industry
 
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OK,here`s another thought..These run through my head pretty fast and escape faster..:p Ok,what if a fellow was to make a barrel clamp say 6-8 inches long,otta some aluminum to save some weight,,have numerous clamp screws along the length,and torque each one say a couple inch pounds more as you go towards the muzzle so as to give the bullet a graduale choke....what say yee??/
 
0 rings

Rubber o rings put along the barrel at about 3ins apart and tune with the last one it might surprize you
 
it makes me think if a barrel could be squeezed down to affect choke.
wouldn't someone make some device to freshen up or tighten the choke
up if it were possible. make a nice choked barrel out of a loose one?
 
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