Out to 100 yds no sweat with M500's and smooth bores. Did take one at 150yds, into a 20 MPH wind. Slug grooved heart but did not penetrate into opp side chest wall. That was a 2 3/4" WW 1 oz foster.
I've had good luck with rifled/tuned 870s. Shots have been 95 yards and under though- ran WW Hi Impact Supreme 2 3/4".
Oh yeah, I buy all my slugs from the same lot #
I did a few yrs ago go old school and try an 870 police magnum, used an Aimtech mount, smoothbore bbl.........Active slugs. The bbl fit badly into the receiver, so I added two layers of masking tape to the degreased flange and then tapped the bbl in with a wood block. Snugged mag cap with
leather and channel lock. Nice n tight and I don't think aligned for odd ringout or over stress. Oh yeah, another thing, I leave the guns together until after season deep clean.
That helped that gun shoot OK, was maybe a 4" rig at 100. Nothing spectacular. Never tried other slugs in it, got a batch at a screamin' good price so set it up for that. Took an 8pt opening day at 25 yards LOL. Slug fragmented on opp shoulder. Not too happy with that, he didn't go too far but should have gone down a little closer IMHO.
Most folks buy slugs from mixed lots, aren't used to the recoil, shoot guns with crappy triggers, improperly set up scopes/rings/bases and take their barrels off and on during season. All those variables can wreak havoc on accuracy and cause frustration.
Frustration alone can make for even worse shooting. High dollar slugs? Can get to frustrated way sooner!
When testing it's best to minimize variables, change things one at a time (if need be).
Most slug guns can shoot better than the person behind them, if some variable minimizing things are done, a good load found, and a decent technique in handling recoil is developed.
I use a pistol case when doing a lot of bench testing and sit pretty upright. Simulates body roll comparable to field positions, big recoil, slow projectiles.........it's important. Cranking a slug gun in a sight vise, leaning way over the bench, don't be surprised if your shots go high when afield.
Seen it over and over.
I like slug guns, they're mean and get the job done!