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STI mag tuning


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Feed lip width per STI info sheet:

38S, 38SC,9mm, 9x23---.355"-.360"

40 S&W---.385"-390"


Other individual mag tuners may have somewhat different dimensions. I tweak mine open with a small crescent wrench. When I am within a couple of thou I polish the inside of the lips with a fine diamond file and then do a final polish on my buffer feeding the lips into the wheel. I measure at the rear, middle and front of the feed lips. If the lips are too wide to begin with I use a brass hammer to close them up.



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Its seems that I'm the exception, but I put guts in a tube and go shoot. No massage required. I have almost 2 dozen STI/ SV mags that all run without adjustment of the feed lips. A couple of the SVs are out of spec and required a little beating to drop free, but they still run.

Why not try and see if they work before worrying about them?

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  • 1 month later...

I ordered them as parts, 3-140's and 1-170 with limcat base pads and I think grams springs and followers as per chuck at shooters connection and my buddy advised. 2 worked like a charm and the other 2 would not even hold the rounds the lips were spread out just a little to much. They are working good now thanks to everyones suggestions. A brass hammer, brass anvil base and a few wacks did some good. Oh ya, dont forget the the filing to get rid of the burrs around the lips. Smooth as silk now.

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  • 5 years later...


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