Quoted:
The S&W 3000 was a fairly close, but NOT exact "clone" of the Remington 870.
It was made in Japan by Howa for S&W.

S&W sold it for some years along with a semi-auto gun by Howa, the Model 1000.
After S&W dropped the guns, Mossberg picked them up and sold them for about 1 year.
Gun Parts Corporation sells most parts under both S&W and Mossberg names.

The 3000 was a good, high quality gun that gained a sort of cult following with some police officers.
However, the intent of the S&W gun was to win the police shotgun market from Remington, but Remington just ate their lunch, which is why S&W dropped it.
Problem was, Remington had and still has something like 95% plus of the Police shotgun market, and too many police departments remembered the disastrous S&W Model 916 that was a major failure for S&W.

The 3000 did sell to the commercial market, but, like the police market, the gun just didn't have enough to offer over the Remington 870, and sales were disappointing.
Most 3000 owners are quite happy with the gun, and they stand up well.

The gun itself is a high quality, well made gun.  "Some" accessories made for the Remington 870 "may" fit the 3000, but barrels and magazine extensions won't.
Choate used to sell 3000 magazine extensions, but I'm not sure if they still do.
Gun Parts sold many police accessories, but I think all they have left are barrels and a folding stock.

All in all, a nice gun that just couldn't compete with Remington.

Quoted:
The S&W 916 was actually the old Noble shotgun design.
S&W decided to get into the police and commercial shotgun market, and bought the Noble design.
Exactly who actually made it is unclear, but build and design quality was bad.

S&W tried to sell the 916 to the police market, but the guns performed so bad, S&W took a hit on their reputation.  Coupled with the high rate of warranty returns from commercial buyers, apparently S&W actually discussed buying all of them back, simply to protect their reputation.

The problem with the 916 was a systemic one.  There was no one or two problems that S&W could work.  A gun would come in with one problem, S&W would fix it and it'd come back with a totally different failure.
This got so bad, most gunsmiths of the day started refusing to take them in for repair for the same reason.
We'd get one in with a broken part, fix it, and it'd come back with a different part broken, with the customer demanding we "stand behind our work" and fix the new problem for free.

To be clear, not ALL of the 916's were bad, but enough were that it caused S&W to take a big hit on their reputation for top quality guns.  It was probably S&W's biggest failure to that time.
A lot of people got 916's that gave no trouble and many are still out there.  From my experience however, once one does have a failure, these tend to cascade with the "fix one part and another breaks".
Since gunsmiths don't see these much these days, many don't know the reputation for trouble, and take one in for repair, often to their regret.

Gun Parts Corp does sell most 916 parts.
If you got a good one, they are quite serviceable.  Start having problems, and things often go south fast.

Quoted:
I just picked one up tonight that was retired from the Fort Lauderdale PD. $125 OTD.