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The  Shotgun  Shop (www.theshotgunshop.net)

P.O.  Box  212, Arnold  MO  63010
636-282-4379
theshotgunshop@hotmail.com

Custom Choke and Barrel Work, all Gauges

Specialty Gunsmithing

Reasons to consider special custom choke work and custom choke tubes

 

  
  Many factory choke tube holes and some aftermarket-type installations are not in line with the bore of the shotgun barrel: in other words, crooked. A choke hole that is misaligned is more likely to not shoot where you expect, and the choke tube that you use will have the performance affected by an angled or off-line condition.

The choke tubes provided for the factory and aftermarket choke holes being installed are ALL made with a lack of precise fit to reduce the possibility of danger from the prevalent off-center condition. In any case, a lack of match between the expected bore size and the manufactured choke size will create an uncertain amount of actual choke, especially if the apparent bore size is unknown. The exit size of a choke at .700” will create different results when used in a bore size of .720” vs. another at .733”. One barrel would be a “modified” choke and the other a “full” choke 12 gauge, but the same tube size is used in both situations.

The tube would have more internal “jump” when in the smaller bore barrel and have less total length of the tube providing any contact and choking action. Some extreme examples can have 40% or more of the tube length be jumped before the shot makes appreciable contact, and that is when the tube is in an aligned hole. Factory and mass-production chokes may be used in a precisely installed hole, but precision overall fit will be lacking. (The threads will necessarily have some clearance tolerance between the tube and hole)

 Exceptions to this situation are possible when a factory tube intended for a standard bore is then installed into a backbored barrel where the bore diameter may happen to be more closely matched to the tube entry end. Occasionally an aftermarket tube installation will be done to a barrel with a bore size close to the maximum that still allows safety clearance. Both situations, when installed with proper alignment to avoid having the tube edge intruding into the bore, will be closer to the ideal custom choke installation but still will be limited by standardized length and choke exit dimensions. The choke will typically be of added constriction compared to standardized markings meant to correlate to a chosen bore size. For example, a choke marked “improved cylinder” may be equated to a full choke, as it was in one particular example done here.

A precision custom choke installation and individually-fit choke tubes have none of the limitations that are present in mass produced choke holes and tubes. The pattern will be more likely to be in line with the point of aim when the tube hole is in alignment with the shotgun bore, and the patterns will likely be more uniform when the shot is constricted evenly through the entire choking action. An off-center choke will have the shot strike first on one side of the choke and have an uneven action. If the tube is held tilted as well, the shot will be forced to change the direction of travel during the choking action. Pellet deformity will be heavier on the shot column side exposed to the angled interference and cannot avoid having a detrimental effect on the pattern uniformity of any shotgun load. Such a tilt may also contribute to different points of impact between open and tight choke tubes.

An open choke may only strike against one side of the shot column to any significant degree. The more complete contact and choking of a tighter choke may guide the shot column more to the off-center side than the open choke.

 

Now that the limitations of mass production chokes and improperly aligned barrel threads has been explained, you can choose to not be limited by the chokes installed in your factory barrel or typically provided from aftermarket installers. Only when you have all of the facts can your decision truly be an informed decision.

The problem of crooked factory choke tubes should be considered whenever purchasing any barrel with tubes already installed. Ideally, if you prefer a particular length, and the barrel has a crooked choke that needs to be replaced, buy the barrel at a length longer than what you want so the barrel can be cut to the preferred length and have a precision hole installed. If that choice is not practical due to circumstances, remember this mantra: a shorter barrel with a straight choke has got to be better than a longer barrel with a crooked choke. Special choke installations can have longer extended choke tubes that eliminate the difference in “feel” of swing by replacing the lost length and mass of the removed barrel section. The main loss is of the rib length, but the tube will never be seen while looking down the barrel.

 

 

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