CHOKE TUBE ERROR RECOGNITION
Many factory shotgun barrels are equipped with interchangeable chokes, and few guns have non-tube barrels as an option anymore. Your most important detail is proving that an acceptable pattern is hitting where you point. The best fit and handling are useless if you fail to hit the target. My first rude example shot 11” high at 19 yards. The hunter owner realized he wasn’t losing his talent after all- at least after the wrong bird fell out of a group. He had been thinking all those misses were HIS fault. The trouble he had just trying to get the factory to replace this dud was a long wait plus a barrel that was only half as far off target. That amount must be what they called “acceptable deviation” for that maker. I believe the BEST warranty is the one that needs to be used LEAST.
Every shooter realizes a rifle with iron or telescopic sight needs work if the sight can’t be adjusted onto the aiming point. BUT! How many even bother to check their shotguns?
Most excuses I hear include: “I’ve never had any problems hitting game and/or making good scores at the range”, “the factory will make it good if I have a problem”, even “I’m not that good a shot anyhow”. Does anyone refuse to believe that (regardless of ability or talent) a straight (or straighter) shooting gun will make any shooter more effective and best for the circumstance?
The fix for a crooked choke starts with a hacksaw and ends with a new straight hole. Now, some people don’t want a shorter barrel, but remember that a shorter barrel that shoots right beats a longer barrel that shoots wrong. The smart move, if possible, is to start by buying the longer barrel that can be cut to the length you want. An older gun/barrel that never had chokes, but can shoot on target now, usually makes a great performing barrel with a custom choke tube installation.
There are two main errors in choke alignment that (in a few cases) can accidentally work together to make a gun hit about straight, but the pattern will not be as smoothly spread as an aligned choke. Error one: tilt, angle (Tower of Pisa) Error two: off centerline but parallel (railroad tracks, not monorail). Usually the two errors are both present to some degree. An open choke (in such a crooked hole) would most likely impact one side of the shot stack much harder than the other, if it even bothered to hit both sides. That situation just can’t be expected to produce a good pattern. Any tube in an angled hole will exert extra force against the shot since the direction change must happen at the same instant as the choking effect. More pellet distortion makes more erratic dispersion.
One more unavoidable situation when using mass produced choke tubes is the jump factor built into the tube. If I installed a new factory-type choke hole (straight) and the shooter uses the factory tubes (to save money), the performance and choices are limited.
Mass production needs tolerance choices, and all tubes are made much bigger than any barrel bore they are likely to encounter, plus a little extra to help minimize dangerous interference from those pesky crooked holes. One example: 12 gauge .728 bore, modified tube of .710 exit diameter, 2” length tube, .746 entry end of tube. Expect the shot to jump more than 25% of the tube prior to contact (in a straight hole).
The best performance involves use of the maximum amount of the choke length, and that means you need custom fit tubes. The examples of crooked chokes show one that has the edge intruding into the bore from the point of view of the shot/wad impact. I have plenty of examples to show much more variety of problems, and I will include more pictures in the future. I hope this information will benefit each one of you.
Factory installation shows poor alignment.
Aftermarket installation with choke edge disappearing from 9 o’clock to 1 o’clock, extremely crooked and DANGEROUS!
This choke is turning inside out and has lost some pieces already. The barrel is bulged and has a split starting at the edge of the rib.
BENEFITS OF PRECISION AND CUSTOM CHOKE WORK
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.
P.O. Box 212, Arnold MO 63010
(636)-282-4379 yourgunsmith@hotmail.com