Quoted: I purchased a Sure fire for my 870 security model (Model 618FA).  I can remove the shot tube extension, but i cant remove the magazine cap.  Unlike the regular model there is no front face to use the Surefire installation tool.  It is hollow.  It seems that Remington over tourqed the cap (Fuck Remington, this is my last 870!  dimples from a past shotgun and now this on the 7-shot model)  Is there any way i can loosen the cap?  I've tried lubricating the threads and lightly tapping on the cap with a small hammer.  I also used an old leather sling to wrap around the groved cap and loosen it by letting the leather grip down.  NO-GO!!    GRrrrrr Will i have to send the weapon to a smith?  If so, who would be a good choice?

Your post is a bit confusing. The SF tool is for taking the standard fore end off of the action bar once you get it all out of the receiver and also for installing the new SF fore end back onto it. The magazine cap should come off with 556A2's method...although I prefer an old leather belt (your old sling will do fine) and channel locks. The HD models need the cap tightened well because they do not use the ball and detent system like the Wingmaster or Police models.

Can you clarify?

WWTim...the Remington extension is not spot welded to the cap, so yes, it will unscrew and leave the cap on the old mag tube if the cap is very tight.

Quoted: Looked up channel-lock and found one in a tool box.   I wrapped the mag cap in a rag and attempted to use them to loosen the cap.  All it did was wear away the finish and dig a groove in the cheap Remington steel which HAD to be screwed on so tight so the gay company could save a few cent on doing away with the detent.  Unless i find a used wingmaster or a Police Model 870 thats built proper i am DONE with Remington products.

Well, I would respectfully suggest you maybe stop a few minutes and get a cold beer or two while you calm down. Your shotgun is a very well made firearm, even if Remington did cut a corner or two so they could sell it $100+ cheaper. My personal opinion (only) is that I would take it over any other pump shotgun made anywhere in the world except, of course, the Wingmaster or Police Model.

The "Channel Locks" we speak of are, of course, Channel Lock pliars as you discovered. If that does not work, and apparently it did not, (leather pads the cap better than the rag) I have had to resort a time or two to use of a small vice. You can use a couple pieces of plywood or such to pad the vice jaws also if the leather keeps slipping. Lock the cap down good, but not TOO hard (if the whole gun moves when you twist it you know it is not tight enough) and try twisting the shotgun while the cap is locked in the vice. This will only, at best, get the cap started, (it will obviously move only a few fractions of an inch) but once started, it should then unscrew with little more problem.

If all else fails, call Remington and send the gun back..they will make it right for you.

Good Luck...hopefully you will be laughing about this next week.