My girlfriend has a 12 gauge cantilevered barrel with a scope mounted.
It had a Red Dot BSA sight. It left something to be desired so I mounted a Bushnell 1-4 scope.
It seemed ok at 50 yds so we moved back to 100 yds.
Groups got big and I don't know why.
Somebody told me maybe we let the barrel get hot and that changed point of impact.
SOS
whelennut

what slugs are you using ? what do you call a big group ?

personally , Ive found that the accuracy claims of slugs at distance are many times greatly exaggerated , including the sabots in rifled barrels


I also dont like most of the cantilever mounts Ive seen.....too much flex

I have found that the Hastings slug barrels were the best performers. Also we found that the Winchester sabots provided the best consistency.
We wire brush the bore and then use a patch with solvent after every 8 to ten shots. Accuracy fell off very quickly with out scrubbing the plastic out of the barrel.
Due to recoil of the 12 ga your shooting platform and bag position are very critical as well as how and where you position the gun.
I have seen some flexible scope bases on the Remington after market barrels and we did not have good luck with them.
We had two 870s drilled and tapped for a top mount weaver base and that worked quite well. The sloppy barrel fit caused groups to be larger so we started testing
the cantilever system.
We hunt in southern Michigan and did have to use shotguns only so we did a lot of experimenting with them
You don't mention the type of gun or barrel so I may not have relevant experience

Remington 870 with scope mounted on barrel not reciever. Hornady 300 grain SST
We got 3 inch group at 50 yds. But 100 yards was giving us flyers a lot bigger.
No way to get your face down on the stock and still see through the scope I will try cleaning the barrel.

my 12 ga rifled barrel will not group the Hornadys very well either........slug barrels can be real fussy about what they shoot , and you will need to experiment with different ammo


a rifled barrel should shoot way better @ 50 yards with a load it likes than 3 inches

Two 870 w rifled bbls.
Non cantilever.
Trigger jobs.
High comb stocks.
Receivers D&T.
WW High Impact Supreme 2 3/4" did under 2" at 100 yds.
Clean/dry bore..............fire a fouler or two. Then clean after next 10 shots.

WW dropped that slug and I quit slug gunning.
Buddy bought one of the guns, he shoots the WW Partitionsabot stuff, says it shoots 3" at 100 yds.
Better shooter proly cut that in half.

Like somebody mentioned in prev post.........bench technique is picky.
You're gonna get smacked.
Soft pistol case between you and gun can help.

FWIW the 4X Leupold compact on my old rig has held up like a champ.

At somewhere between 35 and 70 yards in a non-rifled barrel shotgun slugs tend to tumble, and when that happens the groups blow up huge. Obviously if your barrel is acting like that, rifled or not, tumbling is likely what is happening. Might be a different brand of ammo or different style of slugs will solve it. Might also be that it's not spinning the slugs to stabilize them in which case it could be leaded up from shooting Foster slugs when the barrel needs a saboted slug or a good cleaning with lead remover.. Look carefully down the bore and see if that isn't maybe the case.

Six different smoothbore shotguns, never saw tumbling evidence on paper at 100 yards.

Accuracy was not the best on the Remington 870P, 870 Wingmaster and 1100.
Groups never great, and 75 yards seemed about it for me.
Rifled choketbe helped on the Wingmaster, but would lead up and throw wicked fliers horizontal at 50 (like 6 or 7 inches to the side).

Mossberg 500, was fine at 100. Four different ones.
Accuracy was good to 150 yards, but then one might question slug performance once it landed on the money.
Had one deer shot broadside at 150, slug did not penetrate offside chest wall.

Popped others at 100 with nice exits.

I dug around in the gutpile, never did find it.
Grooved top of the heart though

Kinda known around these parts...........M500 and WW slugs............in smoothbore.............was THE choice back in the day.

The rigs would shoot. Best to buy slugs from one lot # (zero and hunt within lot).
Problem I saw.............most folks running crap scopes............and not being able to handle the recoil.

If I had to run a smoothbore today, I'd buy a Mossberg 500.
Hate the rattle, the top safety too close to scope............but I've seen em shoot just fine.

Rifled, I'd buy my old 870 back off my hunting bud!

Whelennut, I had almost the same setup just a different scope. 2 3/4" copper solids were the most accurate for me.

My brother has the same setup & his gun likes 2 3/4" Remington Copper solids sabots also.

Lightfields will shoot well from most slug guns

I used to hunt with a Winchester 1300 12 ga fully rifled barrel. Started with 3” Remington copper solids and it consistently shot 2” groups at 75 yards. It also left a 3” bruise so I switched to 2,75 copper solids wit equal success and less recoil.
About 5 years ago I got a fully rifled 20 ga barrel for my Encore an it shoots Hornady 250 gr sabots into tight little groups out to 100 yards.

By all means try to start your test session with clean barrel. The plastic from sabots builds up quickly and will affect accuracy. Secondly, try some different brands of slugs. And last but not least, get a comb raiser so that you can get consistently solid cheek weld and sight picture.

ww.accu-riser.com/categories/Accu%252dRiser-Cheek-Pads-and-Comb-Raisers

I shoot Fiocci low recoil slugs for 3 Gun. The accuracy is good and the recoil will make your Girlfriend want some action after sight in...

We are going to try the copper solids as soon as weather permits.
The gun is back from the factory with test target.
No charge, thanks Remington!

Hey guys!

On my Hastings rifled slug barrel, Beretta 390, there is a note - NOT TO USE REM. COPPER SLUGS. I don't know why? I continue to use Lightfield 12 gauge Sabot shells in it as they group well in it. Anyone else see this notation on the bottom of their Hastings {French made} barrel? (It DOES seem to be rather thin, esp, toward the muzzle.)

I intend to try out Win. Sabot slugs before next fall, just to see how they shoot? I have had this Hasting barrel w/ cantilever scope mount for a number of years now. Fun to try a variety of slugs / but a bit brutal..!!

Brittman