Remington 870 question

bspillman · February 7, 2018, 09:37 AM

Hello all. I recently picked up an very nice 870 12 gauge used. On the barrel it says 3 1/2 cinch shells with magnum receiver only. How do I know if I have a magnum receiver? The receiver only reads “Remington 870” then has the serial number on it. Thanks in advance.

Screwball · February 7, 2018, 09:44 AM

If the serial number ends in M, it is a 3” receiver. If it ends in A, it is a 3.5” receiver.

You can put a 3.5” barrel on a 3” receiver... but will only be able to function with 3” shells.

Sharkbite · February 7, 2018, 09:49 AM

And remember the 3” (or 3.5”) length is based on the FIRED (unfolded crimp) length. So, you can fit a 3”shell in a 2.75” chamber and it will fire. But there is no space for the crimp to unfold into. The result is increased and unsafe chamber pressure

Im not sure about the interaction with a 3.5” shell in a 3” chamber. It might not chamber at all. Even if it does, it is not safe to fire.

bspillman · February 8, 2018, 02:09 PM

My serial number is RS17940Z

Virginian · February 8, 2018, 06:05 PM

Ah, the new numbering system tells you NOTHING other than it is a Remington Shotgun - RS. All Supermagnum 3-1/2" receivers are supposed to say that on the receiver, but I wouldn't trust that. Get a FIRED 3-1/2" hull with an unfolded crimp, and put it in the chamber and see if it will eject. If it will you have a Supermagnum receiver. The Supermagnum receiver is different than the 2-3/4" and 3" receivers, but the barrels will interchange.
My bet is you have a regular 3" Magnum receiver, but NOT a 3-1/2" Supermagnum receiver.

Dfariswheel · February 8, 2018, 09:15 PM

The Super Magnum 870 has a longer ejection port.

At least the older models had a piece of black plastic at the rear of the bolt to cover the open space at the rear of the longer ejection port.

If you email Remington and give them the serial number they'll tell you what it is:

https://www.remington.com/support/reach-us

February 7, 2018, 09:37 AM	#1
bspillman Senior Member Join Date: October 28, 2011 Posts: 559	Remington 870 question Hello all. I recently picked up an very nice 870 12 gauge used. On the barrel it says 3 1/2 cinch shells with magnum receiver only. How do I know if I have a magnum receiver? The receiver only reads “Remington 870” then has the serial number on it. Thanks in advance.

February 8, 2018, 06:05 PM	#5
Virginian Senior Member Join Date: February 11, 2012 Location: Williamsburg, Va. Posts: 1,528	Ah, the new numbering system tells you NOTHING other than it is a Remington Shotgun - RS. All Supermagnum 3-1/2" receivers are supposed to say that on the receiver, but I wouldn't trust that. Get a FIRED 3-1/2" hull with an unfolded crimp, and put it in the chamber and see if it will eject. If it will you have a Supermagnum receiver. The Supermagnum receiver is different than the 2-3/4" and 3" receivers, but the barrels will interchange. My bet is you have a regular 3" Magnum receiver, but NOT a 3-1/2" Supermagnum receiver. __________________ What could have happened... did.

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February 7, 2018, 09:44 AM	#2
Screwball Senior Member Join Date: May 16, 2012 Location: ME Posts: 771	If the serial number ends in M, it is a 3” receiver. If it ends in A, it is a 3.5” receiver. You can put a 3.5” barrel on a 3” receiver... but will only be able to function with 3” shells.

February 7, 2018, 09:49 AM	#3
Sharkbite Senior Member Join Date: November 4, 2013 Location: Western slope of Colorado Posts: 3,679	And remember the 3” (or 3.5”) length is based on the FIRED (unfolded crimp) length. So, you can fit a 3”shell in a 2.75” chamber and it will fire. But there is no space for the crimp to unfold into. The result is increased and unsafe chamber pressure Im not sure about the interaction with a 3.5” shell in a 3” chamber. It might not chamber at all. Even if it does, it is not safe to fire.

February 8, 2018, 02:09 PM	#4
bspillman Senior Member Join Date: October 28, 2011 Posts: 559	My serial number is RS17940Z

February 8, 2018, 09:15 PM	#6
Dfariswheel Senior Member Join Date: May 4, 2001 Posts: 7,478	The Super Magnum 870 has a longer ejection port. At least the older models had a piece of black plastic at the rear of the bolt to cover the open space at the rear of the longer ejection port. If you email Remington and give them the serial number they'll tell you what it is: https://www.remington.com/support/reach-us