Here is an E Mail from Remington on the subject of magnum 870's
Subject
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Remington 870
Discussion Thread
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Response (Jonsie) - 09/14/2006 10:22 AM
Dear Jeff;
Thank you for visiting Remington Country! We certainly appreciate you taking the time to write in with your question.Yes, this is correct information for you 870. We would recommend sending your 870 to the authorized Premier Repair center that services NV which is located in Roseville, CA. There contact information is:
J & G Gunsmithing
625 Vernon Street
Roseville, CA 95678
Phone: 916-786-9200
Should you have additional questions, please feel free to contact our Consumer Services Department at 800-243-9700, 9:00 am - 5:00 pm, EST, Monday through Friday.
Customer (Jeff Freitas) - 09/11/2006 08:09 AM
Have an older wingmaster 2 3/4 in only. Was told I could put a 3 in barrel on it and have a magnum ejector installed in the receiver and it would be good to go and run with 3 in shells. What say you,and would Remington install said magnum ejector in said receiver.
Auto-Response - 09/11/2006 08:09 AM
No matches were found.
Question Reference #060911-000006
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So it seems the only difference is the ejector.