So I just got this 870 tactical (I’m a mossberg guy) and Im hoping to get some clarification on this. I’m told I cant swap barrels on this (I dont have any intention on doing this its strictly for HD) and that I cant add a +1 ext. I’m interested in adding this ext.
The extension I have posted is rather small so it shouldnt stick way out but Im told that it wont work period. I got a good deal so Im not worried about one extra shot.
I have that same 870 with the integral 6 rd mag tube (Product # 25077 IIRC). I haven’t installed an extension on mine yet, but I believe you should be able to install one. A fellow over on the shotgunworld forum posted pics of this model with a one shot extension that he installed.
However, the magazine tube, like that on many other Express models, has two raised “dimples” inside (near the muzzle end) that will prevent the extension from working properly unless they are removed. The dimples serve to keep the newer style plastic magazine spring retainer (?) in place when you remove the magazine cap. Some people flatten them out (Midwayusa sells a tool to accomplish this); some people remove them with a Dremel tool.
Removing the dimples probably would mean that you could no longer use the newer style mag retainer if you decided to quit using the extension for some reason. If you removed the extension, you’d probably need to get and use an older style sheet steel magazine retainer instead, and also might need the older style magazine cap. You might also need to have a detent installed on your barrel ring to make the older style cap work right. I’m not positive of that however. The older style mag retainer is a pain in the butt to remove and install based on my limited experience with one on my other 870. That gun is an older 25077 that came with the shorter 4 rd tube and a Rem +2 extension installed, and the barrel came from the factory with the detent installed in the barrel ring that made it compatible with the older style cap and retainer. So I guess I’m saying that once you remove the dimples, going back to the original configuration (with no extension)could be a pain. Hopefully someone who has plowed this ground more thoroughly than I will come along shortly and correct my post if I’m mistaken. Good luck.
On that particular model the barrel ring was moved forward which means you can’t use any other standard 870 barrels.
It is possible to install a +1 extension but you will have to send your barrel out to have a ball detent installed or use a locking wave washer to keep the extension tight.