Improving A Cylinder Bore

Dear Mr. Buck –

I have an Ithaca Model 37 Pump 12 gauge shotgun. The modified choke was too tight for the cover I hunt in for Ruffed Grouse up here in the U.P. of Michigan, so I cut it off. I am concerned it may now be to open. With out having choke tubes added, can you advise me as to how I can get a tighter pattern with my new cylinder barrel. I was hoping to adjust my shotshells for the desired results. How does shot size effect pattern with a constant DRAM rating or, how does DRAM rating effect pattern with a constant shot size.

Thank You Very Much,


Dear Dave,

There is nothing at all wrong with cylinder bore for ruffed grouse. In my SxS grouse gun, my right bbl is cylinder bore and the left is light mod. Cyl will reliably take a grouse out to 30 yards. Hitting the little brutes is the hard part. Grouse is one of the few birds I’ve hunted that can fly and laugh at the same time.

If you want to snug up the pattern you have a number of options. You can experiment with slower powders. Don Zutz always liked Green Dot to heat up the center of his patterns. I’ve had good luck with Unique. The Alliant Powder website lists many 1-1/8 oz 1200 fps loads using Red Dot, the slower Green Dot and the even slower Unique. If you are inclined, do a little experimenting. It’s easy to open patterns with spreader inserts (Polywad Spred-R inserts) and soft shot, but tightening is always harder. Next time, keep the modified choke and use spreaders inserts to open things up. Make your first shot a spreader (opening a 60% modified pattern to about a 50% IC or less) and then the second shot standard for a Modified pattern. By the way, I’ve tried just about all the spreader gizmos on the market and Polywad’s Spred-R insert is the hands down winner.

The other way to “tighten choke” would be to just use a larger shot load. Does the same thing. If you generally use one ounce and raise that 25% to 1-1/4 oz, it’s the same as increasing your choke from cylinder bore’s 40% to Improved cylinder’s 50% as far as pattern density goes. 25% is 25%. In theory, raising your shotload from one ounce to 1-1/2 ounce, an increase of 50%, would increase the pellet count in the pattern circle from the Cylinder Bore 40% to the Modified’s 60%. Obviously, that load would also kill by concussion to, but you get the idea. More is, well, more.

I mention the above approaches because you said that you don’t want to add choke tubes. But that really is the easy way to do it. Over the years I’ve had very good luck with Trulock and Briley chokes. Carlson and Colonial are also popular. The obvious advantage to having the gun screw choked is that you can use it on different game when you wish. Your 37 would be a nice pheasant gun as well as a good grouse gun if you could swap chokes.

Best regards,

Bruce Buck
The Technoid writing for Shotgun Report, LLC
(Often in error. Never in doubt.)

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