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40 mags not fitting the gauge

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Bought this used, it's probably over 10 years old. 

It's set up for limited, but upon gauging, it doesn't fit, by just a little.

Seems the basepad is dawson. Took it apart, it has the grams follower. Does anybody know who made the tube? It has no inscription on it.

How would I be able to fix this to make it fit?



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If it says SNL on the side of the basepad that means "sometimes not legal"

You'll need to get a regular dawson base pad or sometimes referred to as +1 pad

TTI 4mm usually will work also, may need a slight amount of filing to the rear of the feed lips to clear the gauge.

All my Dawson +1 fit without any filing

a few of my TTI 4mm pads had to be filed on the back of the feed lips to clear the gauge.

When you gauge lay the gauge horizontal and just lay the mag in it. No pressure on the pad at all.

Both set-ups hold 20 easily reloadable with either old SVI tubes or old gen1 STI mags

Don't know about the gen2 STI mags 

Good fortune


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Should be an "old-style" SV tube. They are good stuff!

As previous poster mentioned, there are multiple means or dwaling with this issue:

1- Different basepad that is a tiny bit shorter

2- Removing material (small amount) from rear of feed lips, where they are contacting the guage

3- Removing a little material from bottom of basepad

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Can you show the ofher side of the tube with the control rib? It might be an sps tube. Like others have said you can do one of two things, put a different basepad on it, or file a bit of the rear of the feedlips, which is probably what I would do. 

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Could be an SPC tube, the only one I had was soft and wouldn't retain the proper feed lip width.

How many rounds?  My SNL's get 20, reloadable.

You can take a small amount off of the bottom back corner and the SNL's will sometimes fit.  Don't put any kind of tape on the back half of the base pad either.


As long as you don't weaken it you can file the lips down a shade and the base pad a shade to make it fit.  Looks about like my STI/Dawson SNL pad/tube fit was before I started "whittlin" on it.  Now they both fit just fine.

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The basepad does not have any inscription like "SNL" on it.

Called dawson, measure the basepad height, comes to 0.825, according to dawson, that's +1, SNL will measure about 0.885. 

Measured the tube alone, overall back length is 128.5mm. 

I am not confident to file the tube by myself. Anyone has any idea which basepad will make this legal. 

Anyone can identify these tubes?




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On 12/11/2018 at 1:05 PM, anbrumm said:

I'd recommend filing the feed lips a little or try a thinner basepad like the Taran Tacticals.


I wouldn't touch the feed lips on a $100+ no-longer-available, highly desirable mag tube when the solution is readily available for $30.

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47 minutes ago, quliming said:

Thank you guys for the help. SV confirmed this is their old style mag. I also contacted Grams and Beven said his 11mm basepad will work.

If I decide to sell these at some point, how much is this worth?


Check the Classifieds. SV old style mag with Grams guts is worth about $120-$150.

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