I have a Marlin 880 SQ heavy barrel with a cheap 3-9x scope by Simmons.  The first firearm I ever bought, and it was in secret back in highschool in an anti-gun home and state (NY).  I saved up some cash, sold a few things or two for funds, and bought it brand new in the late 90s.  I knew barely anything about guns back then.  

I never really tested it's accuracy in a controlled setting.  The closest to that was hitting small targets at 50 yards (1/5 scale paper animal silhouettes) from a benchrest and I was able to hit them fairly consistently.  I'm guessing this is about 2-3 MOA?  I also would try to hit spent 12ga shotgun shells at 50 yards... hit or miss on those, maybe hitting the shells about 1/2 to 2/3 of the shots.  Not great distance by any means, but tons of fun for my buddies and me considering it was a cheap rifle using the (back then) cheap .22 ammo from 550 round bricks.

Fast forward 15 years... I don't shoot the rifle anymore, not getting rid of it for sentimental reasons, but now wondering what accuracy it is capable of.  I'm thinking of "upgrading" it, focusing on the scope and mount.  I don't want to waste my time and money if it's not going to shoot too much better than what I've already done with it.

Anyone else have one of these rifles?  What accuracy do you think it is capable of with better shooting, match ammo, better scope, etc?  Any suggestions of an upgraded setup?

Mine was more accurate than most can hold with Winchester silver box ammo. The heavy barrel was heavy so I cut 4 inches of length off the barrel, recrowned and loved it. Found another project and sold it. I regret but there are more. Great little rifle!

The 880sq is known for great accuracy, a little trigger work and a solid scope and mount, maybe bedding or pillars and it will shoot alongside almost anything.

My Dad bought one in the late 90's and it was the rifle that really taught me how to shoot. The thing was incredibly accurate with Winchester Power-Points and has racked up thousands of gophers in the time it's been in the family. After I moved away to college Dad put an aftermarket trigger in it and it only got better. Much better.

What Dad did was he drilled a chunk of 2x4 so it would hold a half dozen golf tees. At 25 yards he'd put a tee in each hold and a paintball on each tee. Then he would shoot all the paintballs in 6 or 7 shots and split the tees in 6 or 7 more. Dad's a far better shot than I am but I've seen him do it enough times to know that the gear is definitely up to the task.

Seems like the rifle is more than what I've been giving it credit for.  The heavy barrel (at least mine) isn't set up for iron sights, so I'm guessing you have optics of some sort... so what magnification, mounting, etc?  Any recommendations on triggers?

Try the links from RimefireCentral to get your trigger fixed up first. If you are not happy with the results, then get a Rifle Basix trigger is my suggestion.

As far as magnification, that is up to you and what you will be doing with the rifle, 3-9x is pretty common, but  4-14x,6-24x, and even 8-32x are also well liked for an accurate target gun.

The 880SQ of my Old Man's is set up with a Bushnell Banner 3-9x40. It accurate enough that a 4-12x40 or better would be about perfect for it.

I love my 880SQ...bummer that it's been discontinued.  The 880SQ was suppose to have been made with a "match" grade barrel and I'd believe it since mine is a keeper.

I had mine threaded and with a suppressor, it's my favorite 22LR rifle.

I did lighten the trigger pull with a spring from a pen.

Big +1 on the RifleBasix trigger. I put that trigger in my 882SSV, and it made it into a ground squirrel destroying machine. I promise the crap factory trigger is a bigger problem for you than your mount and cheap scope. Address the trigger first and see how you like it. I think it's less than $100 still, and a 15 minute DIY job to install it.

If you still want to mess with the mount, I'd highly reccomend the Warne .22 rings, or even better, the Burris Signature rimfire rings with the plastic inserts. Both mount up directly on your grooved reciever. Both of those rings are tits, but the Burris ones are my personal favorite. They look better and offer some flexibility with the inserts. Don't worry about adding any rails or additional mounting surfaces or anything. The less crap bolted onto the top of your rifle, the less places you have a chance to lose accuracy by misalignments or other assorted defects and variances in mount equipment.

Thanks all for your suggestions.  Gonna look into the trigger!

Nice to see others have the rifle... None of my shooting  buddies even know the 880.

Match chamber.

880SQ's shoot

Got one & mine is crazy accurate. I have read that early 880SQ models were made with 2000 model barrels. IOW, damn good barrels. No clue if this is true or not, but it's what I've read.

A 880SQ will easily do MOA with ammo that it likes. Yes, tweaking the trigger is a virtual requirement in order to wring the gun's accuracy potential. But find what ammo the gun likes & one will be amazed what a little old $300 rimfire rifle can do.

My .o2

I have a Marlin 880 (not the SQ) and it is one of the most accurate rifles I've ever owned.

I used to use it for aerial clay target shooting and was pretty consistent with it.

It is true

They are D&T for the Marlin 2000 sights

It has been verified by former supervisors from the old North Haven plant several times.

Mine had great accuracy. It was a rifle I grabbed a lot for awhile for the fun and the fact it was hard to miss with it. The only thing I hated was the plastic stock, and at the time there was no wood replacements. I ended up buying another Marlin Bolt action wood stock cheap off ebay, (forgot which one) and adapted it for the SQ. Worked out great and made the rifle even better.