Thanks for your response last week about using polywad spreaders in my 20 gauge 870 Wingmaster. I have used the polywad and it does spread things out…almost too much however, since in my modified choke when patterning there are some big holes at twenty yards…(as an aspiring junior technoid, I have done my share of patterning over the last several weeks!)
I have tried the Ballistic brush wads and they have opened things up too, somewhat less than the polywad spreader, but interestingly, the pattern is wider than high. Another words, the shot string is not circular on the paper. It is at twenty yards or so with a 7/8 ounce load about 20 inches wide but only about 14 inches top to bottom.
I am seriously thinking about just taking it to a gunsmith and open it up permanently. He also does a complete 3 screw in choke job for about $80, and other shooters in the area say he is competent. I am leaning more to just opening up the modified barrel to improved cylinder or skeet. What are the diameters for 20 gauge barrels for improved cylinder and skeet?
Thanks for your responses,
I have gotten half a dozen emails on the Polywad performance. Most readers have had the same results that I experienced – open and uniform patterns. Naturally, if you extend the range too far, the patterns will degrade and become patchy. It doesn’t surprise me that a modified 20 gauge would get patchy at 20 yards with the Polywad. It might be just a little bit too far for it. My .026″ choked 20 gauge FN’s upper barrel was just about perfect at 20 yards with the Polywad. I doubt if your Mod 870 20 gauge had that much choke- more like .015″ to .018″. My guess is that your Mod choke would look about right at 15-17 yards with those Polywad loads. By the time the shot got to 20 yards, the pattern may have gone to pieces. In some barrels, that little disk really spreads them out.
I’ve never tried the Ballistic Brush wads, but I am surprised that they make the pattern wider rather than higher. If that happened in my gun, I would sure start testing it a whole bunch more. While it probably means that you just had a couple of aberrant patterns, if it continues, it means that your 870’s bore and/or choke is seriously out of round. The shell couldn’t be doing by itself as the shell could just as easily be put in the chamber 90 degrees twisted around. It would then toss the patterns higher than wider and you didn’t find that happening.
As to 20 gauge dimensions, the nominal bore size is .615, but it is quite common to have 20s with tighter bores. Overboring is not common in the 20s just yet. Skeet chokes for 20s vary from around .002″ to .007″, with .005″ being quite common. IC for 20s would add a few points, probably maxing out around .008″ or so. There really isn’t any hard and fast rule. Remember, technically (I just love that word!), IC choke is any constriction which will print a 50% pattern in a 30″ circle at 40 yards. The dimensions of the choke that will do that will vary with the individual barrel and the shell selected. Nothing is writ in stone. The choke designation refers to the performance of the choke, not the particular amount of constriction.
The Technoid at <www.ShotgunReport.com>
(Often in error, never in doubt.)