In my other post on this subject, I received so many great suggestions that I did a second mod. I further trimmed the center section down to a length of .280" (I was shooting for .250" but decided to be very careful and .280 is what I ended up with after polishing out the machine marks). The diameter was reduced from the .500 original dimention to .435". (see pic) Using a hard alloy, probably around WWs or a little softer, the cast slugs weigh in at 495 grains. They would go over 500 with a pure lead alloy. (see pic)
I loaded some up and the chronographed velocity was right at 1300 fps. With the first modification, I was using 32.0 gr Unique, Win 209, ACTIV 2 3/4" hull and a Claybuster wad sprayed with Frankfort Arsenal mould release to prevent the wad sticking to the slug, and a plastic over slug disc from Ballistic Products to help make a nice crisp fold crimp.
With the 495gr slug, I dropped the charge to 29.0gr with all other components remaining the same.
Next, I fired three shots at 25 yds, resting my Rem 870 with a 20" rifled barrel with a Weaver K 1.5 Micro Trac, over the top of my car. Again, I achieved phenomenal results. Three shots 5/8" center to center. (see pic). This is much better than I ever thought possible. In fact, this is the tighest group this shotgun has ever shot including groups shot with some very expensive sabot slugs. Muzzle energy is 1800-1900 foot pounds....coupled with the huge frontal area of the slug... will make a very deadly combination.
Can't wait to get to the range.
This mod could be done very carefully using a 1/2" drill in a vise, some files and fine sand paper. Just as long as the center section could be held steady.
Will post more as weather and time permit.
Bearmn56
Montana Territory