Man...talk about crazy...need some opinions. Buddy had a great hunt in Iowa..(he is there now)...even crazier, he had just traded his muzzeloader and didn't have a gun...offered my remington 870 slug gun...rifled barrel...I honestly have never missed a deer with this gun and scored on opening day this year...have even taken some stupid long shots with unbelievable results...225 yard double lung aiming at the top of the back...lots of 100 yarders...he has been at the gun smith most of the day and can't come close to grouping...14 inches left 1st shot 20 inches right second shot...sometimes he misses the entire target...he states he has got it on a shooting table with sand bags and even the gunsmith can't get it to shoot...they took the scope off put another one on...still can't group...even at 70 yards...he is in Iowa me in MI...can't help much...but I was so confident with the gun...always...if I didn't know the gun so well I would say it's knukleballing or tumbling the sabots...I told him to take the sight off and shoot open sights...he also cleaned it three times....any ideas????

All of the obvious issues (loose mounts, defective scope, fouled barrel, etc..) should have already been taken care of by the gunsmith that he took it to.

Is he shooting the same exact sabots that you shoot?

Does he have a proven shooting ability? Is he sensitive to heavy recoil?

It would be interesting to see him shoot an empty slug gun that he thought was loaded and see how much flinching is going on.

I was hoping you would reply....this guy has tons of experience...great hunter...2 elk this year, 5 whitetails...frustrating ...he just went and bought a new slug gun at a discount store to finish his hunt...I don't get why it was all over the map...would a bad scopre allow the shots to go to both sides wildly??? We did check the end cap screw as you had said earlier...gunsmiths (2) only scratched their heads....

There's aren't too many things that can cause bullet impact to vary 3 feet between 2 shots from a bench rest with sand bags fired from 70 yards. Something is loose. Since all the externals have been checked for tightness (Barrel, mounts, rings) the only thing left can be something internal in the scope. But installing a second scope still didn't remedy the issue. 2 bad scopes?? Possible.

Were these quality scopes that were being used?

I would start to suspect mis-aligned scope rings causing the scope tube to flex. But once again, the gunsmiths would have also noticed that when changing the scopes.

Shooting 3" shells in a 2 3/4" chamber?
Extremely crudded up action drastically increasing "lock" time?

I'm out of thoughts.

Have him shoot the gun from a sitting or kneeling position, his butt on the ground, not using sandbags, at 50 yards. If it's better, try placing the gun's receiver, not the fore end, on the sandbags when shooting from the bench. Many firearms (my Savage 99 included) with two piece stocks don't like to be shot with the fore end on a rest.

It could be MANY things. Ammo, shooter, scope, rings, wind, dirty barrel, loose magazine cap. First, don't use cheap scopes on slug guns. They don't last. Even good scopes can have a short life. The recoil is severe. Make sure the scope and thing mounts are good and tight. You can crush a scope, though, if you make them too tight (something to consider on this gun.) Second, when you get the gun back, clean the barrel with something that will get the plastic from the sabots out of the rifling. The products designed for muzzleloaders work well. Third, find a brand of sabots that shoot well in that gun. I have seen drastically different results with different brands of ammo. Some as bad as what you are describing. Generally, the slower the sabot, the more accurate you will be, but you give up distance. I am also assuming your barrel is rifled. If not, well, that is an entirely different matter. Fourth, when you shoot, do it from a bench with bags and hold that barrel down. You can't just touch the trigger like a rifle. Slug guns jump and you have to hold them down. This alone may be the explanation. Good luck.

Tell him to use the same shells you were using and see what happens.
I had the same deal this year and took some time to find the right shells.

I also have an 870 and would be interested in knowing what you found the problem to be. If it wasn't a bad reticle in the scope(s), I'd guess your barrel is moving around in the receiver. I don't think these guns are tack-drivers but your friend's results suggest something is seriously wrong.

IMHO, I believe that 100-125 yds is the max range for a responsible shot with these guns unless you have practiced at this distance and really know the ballistics of your gun/ammo. The longest shot I've made was 92 yrds with near perfect conditions. Beyond that distance the slug drops rapidly and probably begins to tumble - it's a hail mary. If you're off a hair or the animal moves at all in reaction to the shot, you're going to have a bad outcome.

It is good to see these comments by everyone. This is community at it's best.

There's a very simple thing nobody mentioned. Make sure the cap to secure the barrel to the frame is tightened as far as hand tightening can go. Then check it between shots.