Mulling idea of 870 build (but have limited 870 knowledge)

Munkey1973

Munkey1973

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Hey all,
I'm no stranger to doing some custom builds (Rem 700 SA, CZ 457s) but my knowledge of 870 is limited.
I love the look of the 18 inch 870 Marine (as well as the 870 Police)... but of course they're "unobtainium" used or new at the moment.

Long story made short... Ideally I'd like to find a used, and maybe cosmetically abused 870 since I am a professional laser engraver (& intermediate Cerakoter). I am soon to bebranching out into nickel & gold plating as well, and the steel receivers of the 870 actions would be a great canvas.

The thing I really like about them (as well as my Benelli M4), is the look of how the magazine tube is flush with the end of the barrel (3rd photo of actual Marine).

If I were to buy something like a 870 Express (1st photo) with a 4 round mag, could I use a mag extender (like one's sold by the good folks at S&J) to achieve that flush look ?

If its doable, are there any pitfalls to such a build.... or should I just keep watching the market to see what comes available for Marine/Police ?





870 express.jpg

extender.jpg

Marine.jpg
 
The marine and police guns are overpriced for what they are...nothing special

if you are able to finish the gun teh building from a well used 870 makes sense and is fun.

As far as mag tube matching the barrel length just need to match the various aftermarket and or oem rem extenstions to the various or cur down barrels
 
It is perfectly doable, and well below your skill level. Just make sure to properly heat treat it to avoid hydrogen embrittlement post nickel plating. There are shops that do nice nickel plating, after you do all the meticulous prep work of course (polishing).
 
99Solutions said:
It is perfectly doable, and well below your skill level. Just make sure to properly heat treat it to avoid hydrogen embrittlement post nickel plating. There are shops that do nice nickel plating, after you do all the meticulous prep work of course (polishing).
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"Doable" in that you figure the mag extension would end up flush with the barrel ?

Thanks for the tip..I'll have to look into that idea of heat treatment pre-nickel plating.. I got the impression from other guys in the engraving industry that they engrave and plate handgun slides right after cleaning and polishing.
 
Handgun slides likely don’t require the heat treating as they aren’t subject to the pressure barrels are.

Electroless nickel plating is the way to go, but I’m sure you’ve already researched this. Make sure it’s a thin plating as it can be subject to flaking off when too thick. It’s awesome stuff. Beautiful, weather resistant, naturally slick without lube.

Post when you’re done - it’ll be awesome.

I’m not certain which mag extension would work for yours, but a +1 fit perfectly on a 14” barrel.
 
Munkey1973 said:
"Doable" in that you figure the mag extension would end up flush with the barrel ?
Click to expand...
A +1 mag extension is flush with a 14” barrel, the +2 flush with the 18-18.5” barrel and the +3 extension is flush with a 20” barrel.

870 express models have dimples on the mag tube to hold in the mag spring retainer, you will have to either drill out the dimples or swage them flat with a deep well socket. Drilling is quicker but swagging is better looking and there’s no visible holes to potentially let dirt etc into the mag tube, I’ve gone the swagged route.
 
terez said:
The marine and police guns are overpriced for what they are...nothing special

if you are able to finish the gun teh building from a well used 870 makes sense and is fun.

As far as mag tube matching the barrel length just need to match the various aftermarket and or oem rem extenstions to the various or cur down barrels
Click to expand...
Aren't they made with fewer cast parts and better fitting and rust proof finish?
 
If you’re refinishing it anyway I’d get the cheapest old Wingmaster you can find. They are a smoother action and don’t have any of the mim parts that are used in the express to cut costs. Shorten or replace the barrel. Then you can just order a +2 or 3 extension and shorten the barrel perfectly flush if that’s what you want. The express has a plastic trigger guard so you’d have to spray paint it silver to match. The police, marine magnum and Wingmaster have an aluminum trigger guard
 
Butcherbill said:
A +1 mag extension is flush with a 14” barrel, the +2 flush with the 18-18.5” barrel and the +3 extension is flush with a 20” barrel.

870 express models have dimples on the mag tube to hold in the mag spring retainer, you will have to either drill out the dimples or swage them flat with a deep well socket. Drilling is quicker but swagging is better looking and there’s no visible holes to potentially let dirt etc into the mag tube, I’ve gone the swagged route.
Click to expand...

Correction, the +3 S&J extension is NOT flush with a 20" barrel!

It sticks out by 0.5 inches .....
 
geologist said:
Aren't they made with fewer cast parts and better fitting and rust proof finish?
Click to expand...

The 870 Police models are parkerized and go through a more rigorous quality control. They are even sighted in with 1oz foster slugs from the factory .... All the ghost ring 870 Police guns that I have bought and all the rifle sighted 870 Police guns that I bought in the last 10 years were all sighted in to 50 meters. No adjustments needed to the sights.
 
As Butcherbill said .... S&J +1 extension is flush with a 14" barrel ... and the S&J +2 extension is flush with an 18" barrel.


Tac14_Marine_Sept_2020_lowres2.jpg


This 18" 870 one has an extended choke installed, .... the S&J +2 extension is flush with the 18" barrel.

Rem870_Police_GhostRing_MonteCarlo_2021_lowres.jpg
 
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Butcherbill said:
When I looked pics of the rem +3 it seems to only stick out buy the smaller diameter tip of the tube on a 20” barrel.
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I think that’s because it depends on the size of the nut that screws the extension to the magazine tube. The one in this pic looks longer than most and it may be taking up more space. Just my guess, because it looks longer than any of the ones on the mag extensions I’ve handled.
 
Butcherbill said:
When I looked pics of the rem +3 it seems to only stick out buy the smaller diameter tip of the tube on a 20” barrel.
Click to expand...

Well, that gun is an 870 Police with a 20" rifle sighted barrel that I bought last year brand new.
And the +3 S&J extension I also bought brand new from S&J last year ....

And I just measure it .... the mag extension sticks out by 0.5 inches.
 
99Solutions said:
I think that’s because it depends on the size of the nut that screws the extension to the magazine tube. The one in this pic looks longer than most and it may be taking up more space. Just my guess, because it looks longer than any of the ones on the mag extensions I’ve handled.
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99Solutions, what nut are you talking about? The S&J extensions are a one piece construction .... there is no separate nut .....
 
Butcherbill said:
A +1 mag extension is flush with a 14” barrel, the +2 flush with the 18-18.5” barrel and the +3 extension is flush with a 20” barrel.

870 express models have dimples on the mag tube to hold in the mag spring retainer, you will have to either drill out the dimples or swage them flat with a deep well socket. Drilling is quicker but swagging is better looking and there’s no visible holes to potentially let dirt etc into the mag tube, I’ve gone the swagged route.
Click to expand...

Thanks for sharing information. I will likely go with an 18 inch barrel. I think I read somewhere before about the dimples.... yeah, I don't think I'd want to drill them out either. Swage or expand from the inside would be the preferred option. I know that my 1 round S&J extension for my Benelli was OK with the factory spring, I wonder if a 870 with a +2 extension would be OK to use a factory spring ?
 
Ungrateful said:
If you’re refinishing it anyway I’d get the cheapest old Wingmaster you can find. They are a smoother action and don’t have any of the mim parts that are used in the express to cut costs. Shorten or replace the barrel. Then you can just order a +2 or 3 extension and shorten the barrel perfectly flush if that’s what you want. The express has a plastic trigger guard so you’d have to spray paint it silver to match. The police, marine magnum and Wingmaster have an aluminum trigger guard
Click to expand...

I'm glad that you mentioned the trigger guard issue between the models -as I had no idea.... I could not stand the plastic guard on my factory M4. and upgraded to the A&S Engineering Enhanced Trigger Guard.
 
99Solutions said:
I think that’s because it depends on the size of the nut that screws the extension to the magazine tube. The one in this pic looks longer than most and it may be taking up more space. Just my guess, because it looks longer than any of the ones on the mag extensions I’ve handled.
Click to expand...
Factory Rem +3 sticks out the length of the smaller stepped down part, it’s a bayonet lug from what I understand.

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