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S1S90 18.5" magazine capacity?


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I posted this on a different forum but i think i might get a better answer here. I have a M1S90 with a factory +3 mag extension on it. The entire assembled mag tube is right at 18" long. How many rounds should i be able to fit in it? i Keep seeing sights that list it as 7 rounds in the magazine tube. I can only fit 6 light (short) trap loads or 5 S+B 00 buck. I have had it apart and there is no plug in it. It was bought used so the only thing i could guess is maybe it has a odd mag spring in it? Could it be a long spring that takes up a bunch of extra room? How much longer than the magazine tube should a shotgun mag spring be? I know years ago i bought some wolf shotgun mag spring for a Mossy 500. It was a trim to fit spring and i just cut it to the length i needed. What should the length be for a 18" mag tube? Really i would rather use the proper Benelli spring in it. The one that is in it now has both ends bent "flat". It looks like a factory spring that has not been cut. Any suggestions?

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Not all 2.75" cartridges are created equal...remember the 2.75" is the approximate length of the fired cartridge...the actual length of the crimped unfired cartridge may vary by 1/8" or more, depending on manufacturer; when this variance is multiplied by 5-7 cartridges, the difference is enough to change the loaded magazine capacity. Before you start clipping springs, you might do some side-by-side cartridge comparisons and observe the loading differences.


Some of these same cartridge specification differences often account for loading / feeding problems that some experience with their actions, but the action, not the cartridges get identified as the cause.


Just sayin'.






Edited by benelliwerkes
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I think i had it wrong. I tried this morning to load it up with S&B 9 pellet 00 buck. I fit 6 of these in there. I had some Remington number 2 steel shot that i have sitting around. I can fit 7 of these in the tube. So i guess this was all my error. Does anyone know any good 00 buck that is short enough to fit 7 rounds in these?

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