M3 questions

[StreetSweeper56]

I recently acquired an M3 and would like to add a 2 round mag extension. Will that throw off the weight enough to make a big difference to the inertia system? Will the factory spring work or will I need another and where would I get one? I'm not sure if one is included with the extension or not. There doesn't seem to be a lot of aftermarket stuff for the M3. Thanks!

[Doge]

No it won't.

[StreetSweeper56]

27 minutes ago, Doge said:

No it won't.

I assume you mean the weight question. As for the spring, I guess I'll have to test. In my mind, a spring is a spring, they're all sized for 12 gauge so I'd think that one meant for one Benelli would work for another, I may have to trim coils, IDK. I did find a discussion on springs from several years ago, I suppose I'll be the one testing this out. Fortunately springs are not expensive so if I totally botch one up it won't be a big money loss.

[Doge]

I usually use the magazine springs that are included with the kits. Otherwise just estimate about 1 foot/300mm longer than the magazine tube. I have a mix mash of brands from Remington, Wolff, Benelli, and Beretta springs in my guns. I honestly couldn't you tell the difference apart from Wolff is shiny.

[Triode]

I have a M3 and wanted to do the same (add the 2 round extension).  It will not throw weight off as they offer it that way from the factory.  I searched high and low for months, and could not find the Benelli kit in stock (wanted to keep the gun all OEM.)  I used a SuperNova extension kit for a while - it fit/worked; it just was a different length and did not have the barrel clamp in the right spot.  

I finally got tired of the bastardized setup and purchased the full length M3 tube, nut, and the plastic parts from Midwest and swapped the whole thing.  Contrary to what I read online, the plastic pieces did not melt when heating to remove the threadlocker (I bought replacements just in case as they were relatively inexpensive.)  I like the full tube better - the extension made removing the barrel more of a hassle plus the look is a lot cleaner.  I used the barrel clamp from the Supernova kit.

I also swapped the stock with a telescoping one from my SuperNova, and am really happy with the final results.  Below picture is from Benelli (mine has different stock.)  You can see how the full length tubes looks in comparison to the extension. 

[Doge]

On 2/7/2022 at 12:59 PM, Triode said:

Contrary to what I read online, the plastic pieces did not melt when heating to remove the threadlocker (I bought replacements just in case as they were relatively inexpensive.)  I like the full tube better - the extension made removing the barrel more of a hassle plus the look is a lot cleaner.

You gotta keep in the mind the M3 has been around for more than 3 decades. What didn't apply to you is definitely applicable to the older M3s. A super old H&K I had to service had different plastic than a newer one I had. Melted fairly quick because I had to blast more heat on it remove 25+ year old thread locker. Basically I use a blanket statement when I talk about the M3 because there hasn't be a good way to identify the numerous variants of the M3.

Sorta like how the M4 and M1014 get confused with naming. Or a Cerakote and H2O version.

[Triode]

Thanks for the clarification on the issue with plastic melting on earlier versions.  Mine was bought new mid 2021.