Interesting idea. Have you ever patterned the spreader loads to see how the compare to “normal” loads in different chokes?

I did do patterning, and as I recall they opened things up to perhaps LM/IM, with some flyers. With vulnerable birds such as quail, the flyers might have made things almost IC/M in practice.

The shells I used were Polywads. They may be out of business, and fortunately I have some on the shelf. I'm sure there are other spreader makers; no doubt there are others on this thread who know more than I do about alternatives.

RST does have spreader loads available on occasion.

When I was big into reloading in a prior life, I fooled around with some 28 ga. spreader load combinations for my VH 28'M&F upland gun. Tried both the post wad and X - box wad configurations; post wads were OK but the X- box wads were real close range killers; the X-box wads gave near cylinder pattern distribution at 20 yards, hellacious for skeet, woodcock, quail and railbirds. Nearest thing to them available today is Morris Baker's #10 woodcock loads from RST, 2 1/2 or 2 3/4", thank you.

For 12 gauge spreaders, I use, or used, the post wads. As purchased, the post wads didn't work all that well. However, I cut short pieces of fuel line (tubing) and pushed them over the post. This created more disruption of the shot and opened the patterns even more. An added advantage is that it converted a 1 1/8 ounce wad into a 1 ounce wad. I recently found a bag of post wads in my wad stash and may load some when the weather breaks in my garage/loading empire.

The X-stream spreaders from Ballistics products work. I have found they will open patterns from full to modified, modified to improved cylinder. I did not care for the post style spreaders as they left holes in the pattern. The X-spreaders fit in the 12-gauge wads minus an 1/8 oz of shot. When I reload 20 gauge loads, I clip the pedals off the wads in order for them to fit. I do not have any experience reloading 28-gauge rounds.

I had posted the following previously when Spred-R discs were readily available. Unfortunately they are tough to find nowadays, but fortunately, I have a good supply on hand if I ever feel the need for them:

I wanted to see and put on paper what a Spred-R disc did through my 28ga. Repro's FULL (.034 constriction) choke at 15 paces and compare that to the same load w/o a Spred-R disc. So I loaded up a few shells with the Spred-R disc on top of the shot. Yes, the disc is a somewhat snug and tight fit in the AA hull, but as Martha Stewart would say "That's a good thing!" I used my standard Sporting Clays load for comparison:

* 28ga. AA compression formed hull
* W209 primer
* 12.9gr Universal Clays
* CB1075-28 wad
* 3/4 oz. #8 magnum shot
* 1200 FPS
* 10,800 PSI*

* It has been estimated that the addition of a Spred-R disc results in less than a 500 PSI increase in pressure.

The first pic below is the pattern at 15 paces with the Spred-R disc. It resulted in a 19" pattern spread. The second pic is a same load, but w/o the disc. This load resulted in only a 10" maximum spread at the same 15 paces.