Hello,
So I bought an SPR 220 (Baikal IZH 43) 12ga 20" 2 3/4" with screw in chokes.
Got the 45-70 conversion tubes.
Made a rib and front ramp, dakota fixed express rear with a marbles fibre optic front (Green).
45-70 shoots OK need to complete load development.

Live in a shotgun only zone, so decided to get colonial extended rifle chokes (2).
Arrived last week and fitted fine.
Off into my woods I went armed with Federal sabot slugs (older style, hour glass shaped with HP), Remington copper solids, older style (PR12CS) and newer style (PR12RS).
Set up cardboard with white paper and some dots (36" x 42"), paced off 15 yds.
Bang Bang Right Left, Federal's 1.5" low 2 shots in a vertical line 1/2" apart - OK
Friend repeats, Bang Bang Right Left, he covers dot unlike my 6 oclock hold, 4 shots now in a vertical line - OK.
Repeat with Remington (PR12RS) BIG Surprise !
All four enter tree behind target sideways, four perfect side profile keyholes, no exit on 8" rotten dead tree, Federals 6" in dirt after exiting.
Try one of the Remington (PR12CS) round hole, hits tree so hard back falls off and three of the sideways solids fall out of the tree.
HUH !
So today I search and Hasting has a warning on the web that the old Remingtons damage there barrels and the new ones are OK.
Definite velocity and recoil difference between the old and new (New has more of both).

My theory:
Old Remingtons are tighter to the bore but lower velocity and the 1/36" can stabilize.
The new Remingtons and too loose and too fast for the 1/36" twist.

I would not expect then to tumble in 15 yds, that was interesting.

Any thoughts ?

Regards Nitro450exp