SV new-style mag compatibility with old-style SV/STIs

[Kasteel]

I got curious about this, so I emailed SVI Guns and got this reply 58 minutes later:

Mr. Anderson,

The magazine dimensions and tolerances of current and prior magazine

production have not changed.

The billet grip has allowed us to run wider higher capacity magazines

but we still maintain and function/drop check each magazine in a

polymer Infinity grip and magazine release.

The difference in the pre 98 Caspian slide built pistols to the post

98 interchangeable breechface slide should not effect the magazines fitting.

There are differences in design and tolerances of the sti frame. The

internal diameter of the magazine tunnel is narrower as well as the

frame has a additional material underneath the slide stop notch.

Our frames are .700+ diameter through the magazine tunnel and are

machined symmetrically on the ID of the magazine tunnel.

When fitting our magazines to an sti we first machine the frame

symmetrically and increase the magazine tunnel diameter to .700in+.

In addition the sti magazine release is not consistent with the

original 1911 design and requires a larger diameter window or

modification back to the 1911 design with a taper downward from the shelf.

On several occasions I have seen the sti magazine release flat that

is clearanced for the front of the magazine extended in the internal

diameter of the grip creating a drag on the front of the magazine.

Overall there are a few key details to understand when fitting

Infinity magazines to an sti pistol but it can be done by a competent

pistol smith.

Any customers using a factory built polymer grip Infinity pistol and

have issues with new magazine production are fully supported by the factory.

Regards,

Brandon

[AzYooper]

That is exactly how it was for me. I bought a new style SVI magazine and had to do two modifications to get it to work with my STI. I had to enlarge the mag release hole and remove some metal in the magwell area of the frame. I modified the magazine release hole because I wanted to keep my STI mag release for my STI mags. I used a marker to mark the inside of the frame and the mag to see where it would get stuck or be tight in the frame. I then removed a bit of metal in the frame. It was not hard to do.

[Kasteel]

Cool. Will the modified mag run in an SV now? I'd like to come up with a way to run mags in both old style SVs and STis.

[cnote]

Will old style sv mags run in the new grip without mods?

[Julien Boit]

Will old style sv mags run in the new grip without mods?

From my experience, Yes.

I run 4 different brands of mags in my SVs: STI, Rescomp (requires some fitting), SV old styles and SV new styles. All run flawlessly.

The best remains the newest SV mags. All the others are used for training.

Edited November 13, 2013 by Julien Boit

[paopao]

Will old style sv mags run in the new grip without mods?

From my experience, Yes.

I run 4 different brands of mags in my SVs: STI, Rescomp (requires some fitting), SV old styles and SV new styles. All run flawlessly.

The best remains the newest SV mags. All the others are used for training.

What did you do to the rescomp mags? Im having problems with my rescomp mags when im still using my stock sti grip. It wont drop free. After i installed my advance performance grip, it just dropped free!