Hey experts, question about issue with my 12 ga Mossberg 500 (w/ slug cantalever barrel and simmons scope)

Last season I was comming out of the woods and my sling broke, I caught the gun enough that only the barrel hit the ground like this ( \ ) over my back. It plugged with Dirt/gravel/mud...and hit fairly hard. I then gave the barrel a quick wipe down, rag through the barrel with water..then dry rag...and continued to go hunting in the afternoon. I went to sight the gun in to confirm I did not bang my scope out of wack...and it won't shoot accurately. I shot about 12 bullets off sandbags etc...and it won't hit. Some dead center...some way out, no constant grouping. I am willing to change the scope, although I believe the issue may be the crowing in the barrel from what someone explained. Can anyone give me insight on what they believe it could be...and what a repair would cost ? Thanks in advanced.

I'm no expert, but here's what I'd do:

give the whole thing a good cleaning, barrel and action. Take the barrel off and remount it. Examine the muzzle/crown carefully for signs of obvious damage. If there's obvious damage, that's probably it. If not, swap the scope out and try to sight in again. If that doesn't work, I'd take it to a gunsmith. You might have a bent barrel.

Check your muzzle carefully. You may have damaged the very end. That would make the gun shoot erratically. A raised metal bur or even a barrel bent out of round may be affecting the slug as it leaves the muzzle. A gunsmith should be able to tell.

You didn't say whether or not you have already completely removed the scope and remounted it or not... rings, mounts and all...

Other than the above, andremoving and reinstalling the barrel (as mentioned earlier) the only sensible thing left would be to have a smith check the crown and/or anything the smith believes needs to be checked.

what brand of scope? it doesn't take alot of shock or vibration to mess up a cheaper scope. if the scope took any of the impact, you might have broke something inside it.

I'm thinking scope damage or loose rings/bases. Never heard of much of a crown for a slug gun but if the end of the barrel is bent/dented it'll definately cause you problems.

I'd look into the scope/rings/bases first. At least swap out the scope and do some shooting.

I really doubt that being dropped into mud from a few feet up would've BENT THE BARREL.

The previous posts have pretty well covered what could be wrong. Any good gunsmith can inspect your barrel to see if the muzzle has been damaged. If it is out of round, or needs recrowning, he can fix it for you! Merely BENDING the barrel would not result in a scattered grouping such as you are experiencing. All it would do is move the group center to a different point of impact. (Muzzleloader builders bend barrels quite often to get the point of impact to coincide with the line of sight.)

You may need a new scope. I don't know how rugged the current Simmons scopes miught be. The gunsmith can check it for you too. All he needs to do is put an optical collimator into the muzzle, and check the response of the windage & elevation adjustments to ensure they are moving the amount specified for each click......

Ive found that the front rest postion is crucial when shooting a slug gun. Are you resting the mag/receiver or the pump handle on the bag? You need to have the pump handle off the bag and a good rear rest to get any kind of accuracy in a slugger. Most people I see at the range rest the pump on the bag and they always get flyers. Also make sure your barrel screw is very tight aswell as your scope rings.