JeffCooper wrote:I have a pair of 870 police trades on their way to my FFL that have no barrels. The story is that the PD removed the barrels as they were less than the legal length. Fair enough. However, I need a pair of plain-jane 870 barrels, parked and threaded for chokes. 18". Bead sights are fine (I'd prefer none) as I intend to solder LPA front sights on anyway.
The barrels you describe may be tough to find. Most Police barrels have fixed chokes; and the Tactical 870 barrels that are threaded (so they can be sold with the tactical-looking breacher stand-offs) usually have the basic matte finish. You may end up having to have barrels refinished if you want them threaded for chokes
and parkerized.
I'd get in touch with J.D. of AI&P Tactical. He builds combat 870s, and does his own refinishing. You could probably
get some barrels like the ones you describe from him for a fair price, if he isn't too swamped with all that's going on nowadays.
JeffCooper wrote:I'd read that not all 870 barrels are the same in the way they are secured (detents?)...not sure I understand that, and am not sure what to look for when the rcvrs show. Any help would be appreciated!
The barrels on Police 870s and some civilian models have a ball detent in the barrel guide ring. These ball detents are used to lock down magazine caps or extensions.

- Ball detent
- 870 barrel guide ring ball detent_small.JPG (35.34 KiB) Viewed 4422 times
Around 1993, Remington started using a new-style plastic spring retainer on models without tube extensions. These new retainers engaged two bumps in the end of the mag tube, and provided a ratchet system to lock down the magazine cap.

- Synthetic retainer ratchet
- 870 ratchet retainer_small.JPG (32.01 KiB) Viewed 4422 times
(The guy in Wal-Mart looked only slightly concerned when I started taking down the 870 he handed me.)
These were a cost-saving measure, and work well enough for guns without extensions. They're also less of a pain to take out than the older-style, press-in spring retainers. However, the bumps in the magazine tube that these new retainers need to lock in to to work will interfere with the follower if a magazine extension is installed, so they have to be pressed out, filed off, or drilled out.
Barrels for shotguns with this new system do not have ball detents in their guide rings, but it can be added. You can also use a wave-style lockwasher to keep a cap or extension tight.

- Guide ring without ball detent
- barrel guide ring no ball_small.JPG (51.06 KiB) Viewed 4422 times
You can put any 870 barrel on any 870 receiver, as long as the gauge and mag tube length match up; but if the barrel doesn't have the ball detent in the guide ring, unclamped extensions and some styles of magazine caps may work loose during extended shooting sessions.