View Full Version : Got my 870 Marine Magnum.... Couple of questions

November 12, 2006, 05:53 PM
This is my first SG and I need a little help.
I would like to know how to give it a good cleaning.

Do you need to remove the Mag extension to remove the barrel?

What all needs to be lubricated after cleaning?

The manual that came with it is generic for 870's, if someone could tell me how or point me to a good link I would really appreciate it.

Also... the shop gunsmith told me that you could no longer replace the saftey with a lefthanded one. Is this true?

silicon wolverine
November 12, 2006, 07:56 PM
Lefty safetys are obsolete. you might try finding a smith who will retrofit an AR style paddle safety for you.

Yes the mag extension has to come off to remove the barrel.

Clean and lube just like you would any other gun.

There is nothing different between teh 870 MM and regular 870s operations wise. its just stainless/synth.


November 12, 2006, 09:23 PM
In order:
Yes, you have to remove the extension to remove the barrel.
Some new Remington's are leaving the factory with the extension coupling screwed on so tight, owners have had to use padded pliers to get them off.

To remove the barrel, unscrew and remove the barrel clamp screw from the clamp.
Slide the clamp off.
Unscrew the extension tube from the coupling. WARNING: The magazine spring is long and STRONG. It will try to escape from the gun with some force, so take care to keep it under control.
Unscrew the coupling. If it is too tight, use leather or heavy canvas to pad some large pliers to unscrew it.

With the coupling off, finish disassembly per the owner's manual.
When reinstalling the coupling, screw it on just snug, then give it ONE more "click".
You should be able to remove it with just your fingers.

As above, clean and lube like any other gun. A good method is Remington's.
Use a rod, patches, solvent, and bore brush to clean the bore.
Be sure to scrub the chamber thoroughly of powder fouling and plastic fouling.

Spray everything dripping wet with something like CLP Breakfree, or Rem-Oil.
Spray the trigger group to flush out fouling and burned powder particles.
Stand it up to allow it to drain, then shake and wipe off the excess.
Wipe the excess lube and softened fouling off all parts, then reassemble.

You can replace the standard safety with a new left handed safety.
If you decide to replace it, buy a new OLD style safety detent spring and detent ball to go with the safety.
Here's the left-handed safety:

The old style safety spring and detent are parts number 49 and 50.

November 13, 2006, 06:50 AM
Thanks for the responses.

Is the safety swap something a novice can do, or do I need to take it to a gunsmith?


November 13, 2006, 07:05 PM
Unless you have 10 thumbs, it's easy.

Here's how:
At the extreme rear of the trigger group, right above the safety you'll see a small silver cross pin.
Directly above that on top of the group is a hole.

Put your finger over the top hole to catch the spring, and push out the silver cross pin.

Remove the safety detent spring from the top hole, and remove the safety.
NOTE: under the spring is a TINY ball detent. It usually stays in the hole, or can be removed by turning the group over and gently bumping it until the ball drops out.

Lube the safety, ball detent, and detent spring.

Inset the new safety.
Since you'll be replacing the right hand safety with a left hand, be sure the red band is on the RIGHT side of the guard.
Drop the ball in the hole if it was removed, and insert the detent spring in the hole.

Use a small punch or screwdriver to push the detent spring down, and being sure the safety stays in place, push the silver cross pin in from the RIGHT side, being sure the tapered end goes in first.

Test the safety to insure it works properly, and works with a clean "SNAP".

silicon wolverine
November 13, 2006, 07:36 PM
if your MM has the lockable safety, the retrofit wont work, I tried. it is a different assy.


November 13, 2006, 09:11 PM
It does have the J-lock safety.
I don't care for that either.
So does this mean I'm stuck with it?

November 13, 2006, 11:31 PM
Do a search on the forums.
A good number of people have installed old-style safeties on guns with the locking safety with no problems.

They report the safety dropped right in.