Weird. 12 ga Barrel in a 20 gauge 870 receiver?

[enbloc]

Hi All,

I bought a very clean, but used 870 Express 12 gauge shotgun and have not fired it yet. It has a 28" vent-rib barrel with a Rem-Choke.
Bought from a private sale, no documents/manual/cardboard box.


Here's my issue:
After doing a serial number lookup I found that serial numbers on my 870 (RS prefix, U suffix) is a small frame 20ga frame.
It feeds, cycles, chambers and extracts 12ga A-Zoom practice rounds well. Frame is 1.33 inches wide.
I have a spare 18.5 inch 12 ga barrel that fits right in, so I know that the original barrel wasn't modified (If that is even possible?)

It looks just like this receiver. (except for the digits between the 'RS' and the 'U') See note in Post# 3

20190525143026-9111.jpg (797.07 KiB) Viewed 13 times
My questions are:
How does this 20 gauge receiver allow a 12 gauge barrel and mag tube fitment?
Is it safe to fire 12ga through it?
Is this actually a 12ga or a mismatched 12/20ga 870?
What the hell did I buy?

Thanks for any help...

~Enbloc

 

[whatluck]

Rem 870 - 20 Gauge - Large Receiver

Can someone tell me anything about my 870? It looks to be a full-size 870 with a factory 20 Gauge barrel that is made to fit the larger 12Ga barrel port. Are the internals different than a 12Ga? Any special appreciation or disdain for them? Sought after or avoided? Thanks. --M

www.thehighroad.org

There are no 870s that should be avoided save overpriced ones.

Receiver codes on 20 ga. 870s are as listed below, the codes are the last letter in the serial number. Receivers left the factory set up for either 2 3/4" shells or 3" shells and are differentiated by the codes in that regard as well.

Full size frame, 2 3/4" = X ( began production in 1950)

Full size frame, 3" = N (began production in 1962)

Small frame LW 2 3/4" = K (began production in 1972)

Small frame LT-20 3" = U (began production in 1972)

Call Remington's toll free number, work your way through a couple of steps on their phone tree, and give them the model and serial # of your gun. They'll tell you what year it was made. Parts that are interchangeable among gauges are listed thus on the parts list as are parts specific to certain gauges.

hth,

lpl/nc

 

[enbloc]

Thanks whatluck. This 870 was built in the last 5 years so it is not part of the early "full-size" frame with a 'flared' 20ga barrel.

I have found a few internet posts that say that since Remington was bought out by The Freedom Group: (Cerberus) they have changed their Serial Number nomenclature and that

Note: "RS" stands for 'Remington Shotgun" and the "U" no longer denotes "20 gauge" frame. Confirmed by Rem. Customer Support 8/24/2020

I also found that if the receiver is 1.250" wide it is a 20ga receiver.
1.330" wide is a 12ga receiver.

Mine is 1.344" wide.



I have a 18.5" HD barrel that fits right into the receiver, so I'm guessing it is an actual 12ga 870 Express.

Thanks for the help,
~Enbloc

 

[mac1911]

Some where along the line remington dropped different size recievers, heck i think my 552 might be the same size as the smaller 20 g reciever?
It also could have been just in a pile to be built out and got mixed up some how at the factory.
Old nacy on the 20g line might have dropped and Rita on the 12g line picked it up and used it ?
My guess unless there is something that screams unsafe its a 12g

 

[greencobra]

damn it mr. @enbloc, next time do what bigal does, consult us first and you can avoid all this bullshit. promise?

 

[greencobra]

interesting thread though. never seen that before on a 870.

 

[Tinkermatic]

So, your measurements and recent date point to it being a 12ga. receiver, but the serial number points to it being a 20ga.? Is that correct? That sounds like a pickle!

*chuckles in Mossberg*

Edit- looks like you’ve got it sorted, glad to hear it.

 

[enbloc]

Funny thing is, I have 4 other Remmy 870's in various configurations. All 12ga.

This shottie didn't even make me think twice because it looks and is very new.
I bought this shottie because I didn't need the 3" Magnum or 3.5" SuperMagnum chassis for this HD build.
I do however, like researching serial numbers on new (used) firearms to get an Idea when they were made.
That's why I was thrown back to find internet posts that its serial number pointed to a 20ga frame.
I knew early 20ga 870's shared the same receiver chassis as the 12ga 870 and those 20ga barrels had a flared 'ring' to fit the receiver barrel hole.

I'll be calling Remington for a serial number lookup to determine the configuration it left Ilion, New York with.
Besides, if someone modified this from a 20ga to a 12ga... It would have been cheaper to buy a whole new gun...

I intend to make this into a TAC-14 type 'shorty shottie'...
But with a Mass-legal 18-inch HD barrel, heat shroud and a 3-round magazine extension. So, I guess a TAC-18?
I have everything but the extension, which is on back-order...

 

[enbloc]

Just talked to Remington Customer Support and learned:
Shotgun is 12 gauge, built in 2014 and barrel is correct and original.

Thanks for the help guys!
~Enbloc

 

[45collector]

Glad to hear you didn't KB yourself to Valhalla.

 

[enbloc]

Glad to hear you didn't KB yourself to Valhalla.

 

[Rat187]

I have 2 Remingtons 870 in 2 3/4" One a full frame, well used woodcock gun and a newer, actually never shot LW 20G 2 3/4"...both receivers match your 'miked' W dimensions

 

[enbloc]

The photo with the micrometer was from the internet showing the width specs. Mine mic'd out as the 'wide' frame and is a 12g chassis.

What had messed me up was the nomenclature on the Serial Numbers that I found on the internet stating SNs starting with "RS and ending with "U" are exclusively 20 gauge 870 shotguns.
After a little more research and a call to Remington Arms, I found out that they (Remmy) no longer followed that SN format. I updated this and a few other shotgun forums I peruse to show that.
Hopefully others find this data... useful.

Nice pair of 870s Rat...