BlackBore Shotgun Choke Articles
Shotgunners that are concerned with choke performance know to test their shotgun/choke/shotshell combo using the pattern board. There just is not a better way to do it!
The usual way (as all the books/articles, etc. state the procedure) is to set up the pattern paper, step off 40 yards and take the shot. Using a thirty inch circle to encircle the densest portion, you count the pellets and figure the percentages. Using a Cylinder choke (not really a choke, but actually an extension of the barrel bore), the percentage count is supposed to be in the order of 40% at that range. For Improved Cylinder, the percentage is 50%, Modified at 60%, and Full at 70%. Just remember, these are averages and your milage may vary!
Frankly, I don't know any shooter that blasts away using an IC or MOD at forty yards and expects good results! So, let's look at doing pattern testing using a slightly different method.
Why not simply test CYL chokes at 25 yards, IC chokes at 30 yards, MOD chokes at 35 yards and FULL chokes at 40 yards. At these different ranges, the pellet percentage should be near the 70% pellet count for each choke! By using the right choke for the distance, your probability of hits goes up which results in more clays destroyed and more game in the bag. The shooter will have to pay more attention to the distances to the target/game, but the results should be worth the effort.
And, by investing in BlackBore chokes (made from 17-4 PH stainless steel), the shooter knows the choke will work for him/her every time, stopping the wad from "rear-ending" the shot column and eliminating fliers!
As one who owns many shotguns (hunting, competition, testing), I have some thoughts regarding backbored barrels. No great revelations here, but something to consider when reading about the pros and cons of backbored shotgun barrels.
Probably the most often stated advantage for backboring or purchasing a gun with a backbored barrel is that backbored barrels help give better patterns and reduces felt recoil. Let's look at some particulars.
SAAMI dimensions for 12 gauge shotgun barrels specifies .729" as Cylinder bore (manufacturing tolerances +- .002"). This has been the standard bore for many years and many thousands of guns are equipped with these barrels today. But what about factory shotguns that come with "backbored barrels"? Is there a "standard" dimension out there that all manufacturers comply with?
Unfortunately, there is no standard for backbored barrels and with little agreement as to what the bore dimension should be for backbored barrels. Bores range from .733" to .745" or more (the more metal you remove, the lighter the barrel, but also the thinner the walls). As a manufacturer of shotgun chokes and a believer in patterning your shotgun/choke/load combination, I have recovered hundreds of shell wads and recorded the measurements and condition of each one. These wads were recovered after firing through factory and aftermarket non-ported choke tubes, ported chokes and, of course, BlackBore chokes.
An unfired wad removed from a new shell of common, popular shotgun ammo measures about .715" at that point where the petals merge into the body of the wad and .695-.700 for the body itself. When a shotshell wad/shot column is fired in a .729" barrel, the expansion at the wad base is still about .695"-.700", the waist is running about .710" and at the junction where the petals meet the rest of the wad has expanded out to .729". This was especially obvious when shot from the barrel with the BlackBore choke where the blades in the ports mutilated the base, sides of the wad and the petals. It was not so obvious when examining the wad fired through non-ported choke tubes as there is little damage to the wad.
What happens in a backbored barrel? Using the same ammo and recovering the wads, the base and sides of the wads showed expansion to the backbored barrel inside diameter. The petals of the wads are deformed to a greater degree because of the greater amount of expansion. This could indicate a greater potential for pellet deformation (which doesn't help the flight of the pellet to the target).
What's the bottom line? All shotguns tested with backbored barrels gave good patterns using extended conical/parallel chokes. A backbored barrel shotgun may not be the great advantage that so many think it might be! By letting more of the combustion gases escape around the wad/shot column during its journey up the barrel, there might be some lessening of felt recoil, but that is very subjective and hard to prove. I would say that a ported extended choke releasing gases near the muzzle of the barrel would help to reduce felt recoil more, but that is just an opinion. Is there a more likelihood of pellet deformation with a backbored barrel? There are indications that this might be happening, but it is probably not enough that the shooter would recognize the difference from one pattern to the next. Something to keep in mind!
Also, keep in mind that BlackBore Chokes help you shoot your best, no matter if you have a standard barrel or backbored barrel! By consistently slowing the wad at the moment the shot leaves the barrel/choke, the patterns from your shotgun will always be dense and evenly distributed because the wad will not "blow thru" the shot column as the shot exits the barrel!